draft-ietf-nfsv4-flex-files-02.txt   draft-ietf-nfsv4-flex-files-03.txt 
NFSv4 B. Halevy NFSv4 B. Halevy
Internet-Draft T. Haynes Internet-Draft T. Haynes
Intended status: Informational Primary Data Intended status: Informational Primary Data
Expires: April 10, 2015 October 07, 2014 Expires: June 4, 2015 December 01, 2014
Parallel NFS (pNFS) Flexible File Layout Parallel NFS (pNFS) Flexible File Layout
draft-ietf-nfsv4-flex-files-02.txt draft-ietf-nfsv4-flex-files-03.txt
Abstract Abstract
The Parallel Network File System (pNFS) allows a separation between The Parallel Network File System (pNFS) allows a separation between
the metadata and data for a file. The metadata file access is the metadata and data for a file. The metadata file access is
handled via Network File System version 4 (NFSv4) minor version 1 handled via Network File System version 4 (NFSv4) minor version 1
(NFSv4.1) and the data file access is specific to the protocol being (NFSv4.1) and the data file access is specific to the protocol being
used between the client and storage device. The client is informed used between the client and storage device. The client is informed
by the metadata server as to which protocol to use via a Layout Type. by the metadata server as to which protocol to use via a Layout Type.
The Flexible File Layout Type is defined in this document as an The Flexible File Layout Type is defined in this document as an
skipping to change at page 1, line 38 skipping to change at page 1, line 38
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on April 10, 2015. This Internet-Draft will expire on June 4, 2015.
Copyright Notice Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the Copyright (c) 2014 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
skipping to change at page 2, line 15 skipping to change at page 2, line 15
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Definitions . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Definitions . . . . . . . . . . . . . . . . . . . . . . . 3
1.2. Difference Between a Data Server and a Storage Device . . 5 1.2. Difference Between a Data Server and a Storage Device . . 5
1.3. Requirements Language . . . . . . . . . . . . . . . . . . 5 1.3. Requirements Language . . . . . . . . . . . . . . . . . . 5
2. Coupling of Storage Devices . . . . . . . . . . . . . . . . . 5 2. Coupling of Storage Devices . . . . . . . . . . . . . . . . . 6
2.1. LAYOUTCOMMIT . . . . . . . . . . . . . . . . . . . . . . 6 2.1. LAYOUTCOMMIT . . . . . . . . . . . . . . . . . . . . . . 6
2.2. Security Models . . . . . . . . . . . . . . . . . . . . . 6 2.2. Security Models . . . . . . . . . . . . . . . . . . . . . 6
2.3. State and Locking Models . . . . . . . . . . . . . . . . 6 2.3. State and Locking Models . . . . . . . . . . . . . . . . 7
3. XDR Description of the Flexible File Layout Type . . . . . . 7 3. XDR Description of the Flexible File Layout Type . . . . . . 7
3.1. Code Components Licensing Notice . . . . . . . . . . . . 8 3.1. Code Components Licensing Notice . . . . . . . . . . . . 8
4. Device Addressing and Discovery . . . . . . . . . . . . . . . 9 4. Device Addressing and Discovery . . . . . . . . . . . . . . . 9
4.1. ff_device_addr . . . . . . . . . . . . . . . . . . . . . 9 4.1. ff_device_addr4 . . . . . . . . . . . . . . . . . . . . . 9
4.2. Storage Device Multipathing . . . . . . . . . . . . . . . 10 4.2. Storage Device Multipathing . . . . . . . . . . . . . . . 10
5. Flexible File Layout Type . . . . . . . . . . . . . . . . . . 11 5. Flexible File Layout Type . . . . . . . . . . . . . . . . . . 11
5.1. ff_layout4 . . . . . . . . . . . . . . . . . . . . . . . 12 5.1. ff_layout4 . . . . . . . . . . . . . . . . . . . . . . . 12
5.2. Interactions Between Devices and Layouts . . . . . . . . 14
6. Striping via Sparse Mapping . . . . . . . . . . . . . . . . . 14 6. Striping via Sparse Mapping . . . . . . . . . . . . . . . . . 14
7. Recovering from Client I/O Errors . . . . . . . . . . . . . . 14 7. Recovering from Client I/O Errors . . . . . . . . . . . . . . 15
8. Mirroring . . . . . . . . . . . . . . . . . . . . . . . . . . 15 8. Mirroring . . . . . . . . . . . . . . . . . . . . . . . . . . 15
8.1. Selecting a Mirror . . . . . . . . . . . . . . . . . . . 15 8.1. Selecting a Mirror . . . . . . . . . . . . . . . . . . . 16
8.2. Writing to Mirrors . . . . . . . . . . . . . . . . . . . 16 8.2. Writing to Mirrors . . . . . . . . . . . . . . . . . . . 17
8.3. Metadata Server Resilvering of the File . . . . . . . . . 16 8.3. Metadata Server Resilvering of the File . . . . . . . . . 17
9. Flexible Files Layout Type Return . . . . . . . . . . . . . . 16 9. Flexible Files Layout Type Return . . . . . . . . . . . . . . 17
9.1. ff_ioerr . . . . . . . . . . . . . . . . . . . . . . . . 17 9.1. I/O Error Reporting . . . . . . . . . . . . . . . . . . . 18
9.2. ff_iostats . . . . . . . . . . . . . . . . . . . . . . . 18 9.1.1. ff_ioerr4 . . . . . . . . . . . . . . . . . . . . . . 18
9.3. ff_layoutreturn . . . . . . . . . . . . . . . . . . . . . 19 9.2. Layout Usage Statistics . . . . . . . . . . . . . . . . . 19
10. Flexible Files Layout Type LAYOUTERROR . . . . . . . . . . . 19 9.2.1. ff_io_latency4 . . . . . . . . . . . . . . . . . . . 19
11. Flexible Files Layout Type LAYOUTSTATS . . . . . . . . . . . 19 9.2.2. ff_layoutupdate4 . . . . . . . . . . . . . . . . . . 19
12. Flexible File Layout Type Creation Hint . . . . . . . . . . . 20 9.2.3. ff_iostats4 . . . . . . . . . . . . . . . . . . . . . 20
12.1. ff_layouthint4 . . . . . . . . . . . . . . . . . . . . . 20 9.3. ff_layoutreturn4 . . . . . . . . . . . . . . . . . . . . 21
13. Recalling Layouts . . . . . . . . . . . . . . . . . . . . . . 20 10. Flexible Files Layout Type LAYOUTERROR . . . . . . . . . . . 21
13.1. CB_RECALL_ANY . . . . . . . . . . . . . . . . . . . . . 21 11. Flexible Files Layout Type LAYOUTSTATS . . . . . . . . . . . 21
14. Client Fencing . . . . . . . . . . . . . . . . . . . . . . . 21 12. Flexible File Layout Type Creation Hint . . . . . . . . . . . 21
15. Security Considerations . . . . . . . . . . . . . . . . . . . 22 12.1. ff_layouthint4 . . . . . . . . . . . . . . . . . . . . . 22
16. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 22 13. Recalling Layouts . . . . . . . . . . . . . . . . . . . . . . 22
17. References . . . . . . . . . . . . . . . . . . . . . . . . . 23 13.1. CB_RECALL_ANY . . . . . . . . . . . . . . . . . . . . . 22
17.1. Normative References . . . . . . . . . . . . . . . . . . 23 14. Client Fencing . . . . . . . . . . . . . . . . . . . . . . . 23
17.2. Informative References . . . . . . . . . . . . . . . . . 23 15. Security Considerations . . . . . . . . . . . . . . . . . . . 24
Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . 24 15.1. Kerberized File Access . . . . . . . . . . . . . . . . . 24
Appendix B. RFC Editor Notes . . . . . . . . . . . . . . . . . . 24 15.1.1. Loosely Coupled . . . . . . . . . . . . . . . . . . 24
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 24 15.1.2. Tightly Coupled . . . . . . . . . . . . . . . . . . 25
16. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 25
17. References . . . . . . . . . . . . . . . . . . . . . . . . . 25
17.1. Normative References . . . . . . . . . . . . . . . . . . 25
17.2. Informative References . . . . . . . . . . . . . . . . . 26
Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . 26
Appendix B. RFC Editor Notes . . . . . . . . . . . . . . . . . . 26
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 27
1. Introduction 1. Introduction
In the parallel Network File System (pNFS), the metadata server In the parallel Network File System (pNFS), the metadata server
returns Layout Type structures that describe where file data is returns Layout Type structures that describe where file data is
located. There are different Layout Types for different storage located. There are different Layout Types for different storage
systems and methods of arranging data on storage devices. This systems and methods of arranging data on storage devices. This
document defines the Flexible File Layout Type used with file-based document defines the Flexible File Layout Type used with file-based
data servers that are accessed using the Network File System (NFS) data servers that are accessed using the Network File System (NFS)
protocols: NFSv3 [RFC1813], NFSv4 [RFC3530], NFSv4.1 [RFC5661], and protocols: NFSv3 [RFC1813], NFSv4 [RFC3530], NFSv4.1 [RFC5661], and
skipping to change at page 3, line 30 skipping to change at page 3, line 38
yet the requirements for the protocol are specified in [RFC5661] and yet the requirements for the protocol are specified in [RFC5661] and
clarified in [pNFSLayouts]. clarified in [pNFSLayouts].
1.1. Definitions 1.1. Definitions
control protocol: is a set of requirements for the communication of control protocol: is a set of requirements for the communication of
information on layouts, stateids, file metadata, and file data information on layouts, stateids, file metadata, and file data
between the metadata server and the storage devices (see between the metadata server and the storage devices (see
[pNFSLayouts]). [pNFSLayouts]).
Client-side Mirroring: is when the client and not the server is
responsible for updating all of the mirrored copies of a file.
data file: is that part of the file system object which describes data file: is that part of the file system object which describes
the payload and not the object. E.g., it is the file contents. the payload and not the object. E.g., it is the file contents.
Data Server (DS): is one of the pNFS servers which provide the Data Server (DS): is one of the pNFS servers which provide the
contents of a file system object which is a regular file. contents of a file system object which is a regular file.
Depending on the layout, there might be one or more data servers Depending on the layout, there might be one or more data servers
over which the data is striped. Note that while the metadata over which the data is striped. Note that while the metadata
server is strictly accessed over the NFSv4.1 protocol, depending server is strictly accessed over the NFSv4.1 protocol, depending
on the Layout Type, the data server could be accessed via any on the Layout Type, the data server could be accessed via any
protocol that meets the pNFS requirements. protocol that meets the pNFS requirements.
skipping to change at page 4, line 31 skipping to change at page 4, line 43
metadata file: is that part of the file system object which metadata file: is that part of the file system object which
describes the object and not the payload. E.g., it could be the describes the object and not the payload. E.g., it could be the
time since last modification, access, etc. time since last modification, access, etc.
Metadata Server (MDS): is the pNFS server which provides metadata Metadata Server (MDS): is the pNFS server which provides metadata
information for a file system object. It also is responsible for information for a file system object. It also is responsible for
generating layouts for file system objects. Note that the MDS is generating layouts for file system objects. Note that the MDS is
responsible for directory-based operations. responsible for directory-based operations.
Mirror: is a copy of a file. While mirroring can be used for Mirror: is a copy of a file. While mirroring can be used for
backing up a file, the copies can be distrbuted such that each backing up a file, the copies can be distributed such that each
remote site has a locally cached copy. Note that if one copy of remote site has a locally cached copy. Note that if one copy of
the mirror is updated, then all copies must be updated. the mirror is updated, then all copies must be updated.
Object Layout Type: is a Layout Type in which the storage devices Object Layout Type: is a Layout Type in which the storage devices
are accessed via the OSD protocol [ANSI400-2004]. It is defined are accessed via the OSD protocol [ANSI400-2004]. It is defined
in [RFC5664]. in [RFC5664].
recalling a layout: is when the metadata server uses a back channel recalling a layout: is when the metadata server uses a back channel
to inform the client that the layout is to be returned in a to inform the client that the layout is to be returned in a
graceful manner. Note that the client could be able to flush any graceful manner. Note that the client could be able to flush any
skipping to change at page 9, line 25 skipping to change at page 9, line 33
/// */ /// */
/// ///
4. Device Addressing and Discovery 4. Device Addressing and Discovery
Data operations to a storage device require the client to know the Data operations to a storage device require the client to know the
network address of the storage device. The NFSv4.1 GETDEVICEINFO network address of the storage device. The NFSv4.1 GETDEVICEINFO
operation (Section 18.40 of [RFC5661]) is used by the client to operation (Section 18.40 of [RFC5661]) is used by the client to
retrieve that information. retrieve that information.
4.1. ff_device_addr 4.1. ff_device_addr4
The ff_device_addr data structure is returned by the server as the The ff_device_addr4 data structure is returned by the server as the
storage protocol specific opaque field da_addr_body in the storage protocol specific opaque field da_addr_body in the
device_addr4 structure by a successful GETDEVICEINFO operation. device_addr4 structure by a successful GETDEVICEINFO operation.
/// struct ff_device_addr { /// struct ff_device_addr4 {
/// multipath_list4 ffda_netaddrs; /// multipath_list4 ffda_netaddrs;
/// uint32_t ffda_version; /// uint32_t ffda_version;
/// uint32_t ffda_minorversion; /// uint32_t ffda_minorversion;
/// uint32_t ffda_rsize; /// uint32_t ffda_rsize;
/// uint32_t ffda_wsize; /// uint32_t ffda_wsize;
/// bool ffda_tightly_coupled; /// bool ffda_tightly_coupled;
/// }; /// };
/// ///
The ffda_netaddrs field is used to locate the storage device. It The ffda_netaddrs field is used to locate the storage device. It
MUST be set by the server to a list holding one or more of the device MUST be set by the server to a list holding one or more of the device
network addresses. network addresses.
The ffda_version and ffda_minorversion represent the NFS protocol to The ffda_version and ffda_minorversion represent the NFS protocol to
be used to access the storage device. This layout specification be used to access the storage device. This layout specification
defines the semantics for ffda_versions 3 and 4. If ffda_version defines the semantics for ffda_versions 3 and 4. If ffda_version
skipping to change at page 11, line 30 skipping to change at page 11, line 36
the data consist of exact replicas. the data consist of exact replicas.
5. Flexible File Layout Type 5. Flexible File Layout Type
The layout4 type is defined in [RFC5662] as follows: The layout4 type is defined in [RFC5662] as follows:
enum layouttype4 { enum layouttype4 {
LAYOUT4_NFSV4_1_FILES = 1, LAYOUT4_NFSV4_1_FILES = 1,
LAYOUT4_OSD2_OBJECTS = 2, LAYOUT4_OSD2_OBJECTS = 2,
LAYOUT4_BLOCK_VOLUME = 3, LAYOUT4_BLOCK_VOLUME = 3,
LAYOUT4_FLEX_FILES = 0x80000004 LAYOUT4_FLEX_FILES = 0x80000005
[[RFC Editor: please modify the LAYOUT4_FLEX_FILES [[RFC Editor: please modify the LAYOUT4_FLEX_FILES
to be the layouttype assigned by IANA]] to be the layouttype assigned by IANA]]
}; };
struct layout_content4 { struct layout_content4 {
layouttype4 loc_type; layouttype4 loc_type;
opaque loc_body<>; opaque loc_body<>;
}; };
struct layout4 { struct layout4 {
offset4 lo_offset; offset4 lo_offset;
length4 lo_length; length4 lo_length;
layoutiomode4 lo_iomode; layoutiomode4 lo_iomode;
layout_content4 lo_content; layout_content4 lo_content;
}; };
[[AI10: Remember, using experimental version number to track changes
to the XDR via LAYOUT4_FLEX_FILES! --TH]]
This document defines structure associated with the layouttype4 value This document defines structure associated with the layouttype4 value
LAYOUT4_FLEX_FILES. [RFC5661] specifies the loc_body structure as an LAYOUT4_FLEX_FILES. [RFC5661] specifies the loc_body structure as an
XDR type "opaque". The opaque layout is uninterpreted by the generic XDR type "opaque". The opaque layout is uninterpreted by the generic
pNFS client layers, but obviously must be interpreted by the Flexible pNFS client layers, but obviously must be interpreted by the Flexible
File Layout Type implementation. This section defines the structure File Layout Type implementation. This section defines the structure
of this opaque value, ff_layout4. of this opaque value, ff_layout4.
5.1. ff_layout4 5.1. ff_layout4
/// struct ff_data_server4 { /// struct ff_data_server4 {
skipping to change at page 12, line 46 skipping to change at page 12, line 49
layout segment. Each layout segment MAY represent different striping layout segment. Each layout segment MAY represent different striping
parameters, applying respectively only to the layout segment byte parameters, applying respectively only to the layout segment byte
range. range.
The ffl_stripe_unit field is the stripe unit size in use for the The ffl_stripe_unit field is the stripe unit size in use for the
current layout segment. The number of stripes is given inside each current layout segment. The number of stripes is given inside each
mirror by the number of elements in ffm_data_servers. If the number mirror by the number of elements in ffm_data_servers. If the number
of stripes is one, then the value for ffl_stripe_unit MUST default to of stripes is one, then the value for ffl_stripe_unit MUST default to
zero. The only supported mapping scheme is sparse and is detailed in zero. The only supported mapping scheme is sparse and is detailed in
Section 6. Note that there is an assumption here that both the Section 6. Note that there is an assumption here that both the
stripe unit size and the number of of stripes is the same across all stripe unit size and the number of stripes is the same across all
mirrors. mirrors.
The ffl_mirrors field is the array of mirrored storage devices which The ffl_mirrors field is the array of mirrored storage devices which
provide the storage for the current stripe, see Figure 1. provide the storage for the current stripe, see Figure 1.
+-----------+ +-----------+
| | | |
| | | |
| File | | File |
| | | |
skipping to change at page 13, line 43 skipping to change at page 13, line 46
data file. data file.
ffds_fhandle provides the filehandle of the data file on the given ffds_fhandle provides the filehandle of the data file on the given
storage device. For tight coupling, ffds_stateid provides the storage device. For tight coupling, ffds_stateid provides the
stateid to be used by the client to access the file. For loose stateid to be used by the client to access the file. For loose
coupling and a NFSv4 storage device, the client may use an anonymous coupling and a NFSv4 storage device, the client may use an anonymous
stateid to perform I/O on the storage device as there is no use for stateid to perform I/O on the storage device as there is no use for
the metadata server stateid (no control protocol). In such a the metadata server stateid (no control protocol). In such a
scenario, the server MUST set the ffds_stateid to be zero. scenario, the server MUST set the ffds_stateid to be zero.
For NFSv3 storage devices, ffds_auth provides the RPC credentials to For loosely coupled storage devices, ffds_auth provides the RPC
be used by the client to access the data files. For NFSv4.x storage credentials to be used by the client to access the data files. For
devices, the server SHOULD use the AUTH_NONE flavor and a zero length tightly coupled storage devices, the server SHOULD use the AUTH_NONE
opaque body to minimize the returned structure length. The client flavor and a zero length opaque body to minimize the returned
MUST ignore ffds_auth in this case. [[AI6: Even for tightly coupled structure length. I.e., if ffda_tightly_coupled (see Section 4.1) is
systems, that cannot be correct! --TH]] set, then the client MUST ignore ffds_auth in this case.
ffds_efficiency describes the metadata server's evaluation as to the ffds_efficiency describes the metadata server's evaluation as to the
effectiveness of each mirror. Note that this is per layout and not effectiveness of each mirror. Note that this is per layout and not
per device as the metric may change due to perceived load, per device as the metric may change due to perceived load,
availability to the metadata server, etc. Higher values denote availability to the metadata server, etc. Higher values denote
higher perceived utility. The way the client can select the best higher perceived utility. The way the client can select the best
mirror to access is discussed in Section 8.1. mirror to access is discussed in Section 8.1.
5.2. Interactions Between Devices and Layouts
In [RFC5661], the File Layout Type is defined such that the
relationship between multipathing and filehandles can result in
either 0, 1, or N filehandles (see Section 13.3). Some rationals for
this are clustered servers which share the same filehandle or
allowing for multiple read-only copies of the file on the same
storage device. In the Flexible File Layout Type, there is only one
filehandle, independent of the multipathing being used. If the
metadata server wants to provide multiple read-only copies of the
same file on the same storage device, then it should provide multiple
ff_device_addr4, each as a mirror. The client can then determine
that since the ffds_fhandle are different, then there a multiple
copies of the file available.
If the metadata server wants to allow access to the file with
different versions and/or minor versions of NFS, then for each
allowed version and/or minor version, a new ff_device_addr4 must be
defined. The client should not assume any relationship (or lack of
relationship) between the filehandles presented in ffds_fhandle.
I.e., even if the filehandles are binary equivalent for different
versions, they may have varying semantics.
6. Striping via Sparse Mapping 6. Striping via Sparse Mapping
While other Layout Types support both dense and sparse mapping of While other Layout Types support both dense and sparse mapping of
logical offsets to phyisical offsets within a file (see for example logical offsets to phyisical offsets within a file (see for example
Section 13.4 of [RFC5661]), the Flexible File Layout Type only Section 13.4 of [RFC5661]), the Flexible File Layout Type only
supports a sparse mapping. supports a sparse mapping.
With sparse mappings, the logical offset within a file (L) is also With sparse mappings, the logical offset within a file (L) is also
the physical offset on the storage device. As detailed in the physical offset on the storage device. As detailed in
Section 13.4.4 of [RFC5661], this results in holes across each Section 13.4.4 of [RFC5661], this results in holes across each
skipping to change at page 14, line 37 skipping to change at page 15, line 22
N: stripe number N: stripe number
N = L / S N = L / S
7. Recovering from Client I/O Errors 7. Recovering from Client I/O Errors
The pNFS client may encounter errors when directly accessing the The pNFS client may encounter errors when directly accessing the
storage devices. However, it is the responsibility of the metadata storage devices. However, it is the responsibility of the metadata
server to recover from the I/O errors. When the LAYOUT4_FLEX_FILES server to recover from the I/O errors. When the LAYOUT4_FLEX_FILES
layout type is used, the client MUST report the I/O errors to the layout type is used, the client MUST report the I/O errors to the
server at LAYOUTRETURN time using the ff_ioerr structure (see server at LAYOUTRETURN time using the ff_ioerr4 structure (see
Section 9.1). Section 9.1.1).
The metadata server analyzes the error and determines the required The metadata server analyzes the error and determines the required
recovery operations such as recovering media failures or recovery operations such as recovering media failures or
reconstructing missing data files. reconstructing missing data files.
The metadata server SHOULD recall any outstanding layouts to allow it The metadata server SHOULD recall any outstanding layouts to allow it
exclusive write access to the stripes being recovered and to prevent exclusive write access to the stripes being recovered and to prevent
other clients from hitting the same error condition. In these cases, other clients from hitting the same error condition. In these cases,
the server MUST complete recovery before handing out any new layouts the server MUST complete recovery before handing out any new layouts
to the affected byte ranges. to the affected byte ranges.
skipping to change at page 15, line 32 skipping to change at page 16, line 17
Figure 1). Figure 1).
The metadata server is responsible for determining the number of The metadata server is responsible for determining the number of
mirrored copies and the location of each mirror. While the client mirrored copies and the location of each mirror. While the client
may provide a hint to how many copies it wants (see Section 12), the may provide a hint to how many copies it wants (see Section 12), the
metadata server can ignore that hint and in any event, the client has metadata server can ignore that hint and in any event, the client has
no means to dictate neither the storage device (which also means the no means to dictate neither the storage device (which also means the
coupling and/or protocol levels to access the file) nor the location coupling and/or protocol levels to access the file) nor the location
of said storage device. of said storage device.
The updating of mirrored files is done via client-side mirroring.
With this approach, the client is responsible for making sure
modifications get to all copies of the file it is informed of via the
layout. If a file is being resilvered to a storage device, that
mirrored copy will not be in the layout. Thus the metadata server
MUST update that copy until the client is presented it in a layout.
Also, if the client is writing to the file via the metadata server,
e.g., using an earlier version of the protocol, then the metadata
server MUST update all copies of the mirror. As seen in Section 8.3,
during the resilvering, the layout is recalled, and the client has to
make modifications via the metadata server.
8.1. Selecting a Mirror 8.1. Selecting a Mirror
When the metadata server grants a layout to a client, it can let the When the metadata server grants a layout to a client, it can let the
client know how fast it expects each mirror to be once the request client know how fast it expects each mirror to be once the request
arrives at the storage devices via the ffds_efficiency member. While arrives at the storage devices via the ffds_efficiency member. While
the algorithms to calculate that value are left to the metadata the algorithms to calculate that value are left to the metadata
server implementations, factors that could contribute to that server implementations, factors that could contribute to that
calculation include speed of the storage device, physical memory calculation include speed of the storage device, physical memory
available to the device, operating system version, current load, etc. available to the device, operating system version, current load, etc.
However, what SHOULD not be involved in that calculation is a However, what SHOULD not be involved in that calculation is a
perceived network distance between the client and the storage device. perceived network distance between the client and the storage device.
The client is better situated for making that determination based on The client is better situated for making that determination based on
past interaction with the storage device over the different available past interaction with the storage device over the different available
network intefaces bewteen the two. I.e., the metadata server might network interfaces between the two. I.e., the metadata server might
not know about a transient outage between the client and storage not know about a transient outage between the client and storage
device because it has no presence on the given subnet. device because it has no presence on the given subnet.
As such, it is the client which decides which mirror to access for As such, it is the client which decides which mirror to access for
reading the file. The requirements for writing to a mirrored file reading the file. The requirements for writing to a mirrored file
are presented below. are presented below.
8.2. Writing to Mirrors 8.2. Writing to Mirrors
The client is responsible for updating all mirrored copies of the The client is responsible for updating all mirrored copies of the
skipping to change at page 16, line 38 skipping to change at page 17, line 34
The metadata server may elect to create a new mirror of the file at The metadata server may elect to create a new mirror of the file at
any time. This might be to resilver a copy on a storage device which any time. This might be to resilver a copy on a storage device which
was down for servicing, to provide a copy of the file on storage with was down for servicing, to provide a copy of the file on storage with
different storage performance characteristics, etc. As the client different storage performance characteristics, etc. As the client
will not be aware of the new mirror and the metadata server will not will not be aware of the new mirror and the metadata server will not
be aware of updates that the client is making to the file, the be aware of updates that the client is making to the file, the
metadata server MUST recall the writable layout segment(s) that it is metadata server MUST recall the writable layout segment(s) that it is
resilvering. If the client issues a LAYOUTGET for a writable layout resilvering. If the client issues a LAYOUTGET for a writable layout
segment which is in the process of being resilvered, then the segment which is in the process of being resilvered, then the
metadata server MUST deny that request with a NFS4ERR_LAYOUTTRYLATER. metadata server MUST deny that request with a NFS4ERR_LAYOUTTRYLATER.
The client can then perform the IO through the metadata server. The client can then perform the I/O through the metadata server.
9. Flexible Files Layout Type Return 9. Flexible Files Layout Type Return
layoutreturn_file4 is used in the LAYOUTRETURN operation to convey layoutreturn_file4 is used in the LAYOUTRETURN operation to convey
layout-type specific information to the server. It is defined in layout-type specific information to the server. It is defined in
[RFC5661] as follows: [RFC5661] as follows:
struct layoutreturn_file4 { struct layoutreturn_file4 {
offset4 lrf_offset; offset4 lrf_offset;
length4 lrf_length; length4 lrf_length;
skipping to change at page 17, line 30 skipping to change at page 18, line 21
struct LAYOUTRETURN4args { struct LAYOUTRETURN4args {
/* CURRENT_FH: file */ /* CURRENT_FH: file */
bool lora_reclaim; bool lora_reclaim;
layoutreturn_stateid lora_recallstateid; layoutreturn_stateid lora_recallstateid;
layouttype4 lora_layout_type; layouttype4 lora_layout_type;
layoutiomode4 lora_iomode; layoutiomode4 lora_iomode;
layoutreturn4 lora_layoutreturn; layoutreturn4 lora_layoutreturn;
}; };
If the lora_layout_type layout type is LAYOUT4_FLEX_FILES, then the If the lora_layout_type layout type is LAYOUT4_FLEX_FILES, then the
lrf_body opaque value is defined by the ff_layoutreturn4 type. The lrf_body opaque value is defined by ff_layoutreturn4 (See
new type allows the client to report I/O error information or layout Section 9.3). It allows the client to report I/O error information
usage statistics back to the metadata server as defined below. or layout usage statistics back to the metadata server as defined
below.
9.1. ff_ioerr 9.1. I/O Error Reporting
9.1.1. ff_ioerr4
/// struct ff_ioerr4 { /// struct ff_ioerr4 {
/// offset4 ffie_offset; /// offset4 ffie_offset;
/// length4 ffie_length; /// length4 ffie_length;
/// stateid4 ffie_stateid; /// stateid4 ffie_stateid;
/// device_error4 ffie_errors; /// device_error4 ffie_errors;
/// }; /// };
/// ///
Recall that [NFSv42] defines device_error4 as: Recall that [NFSv42] defines device_error4 as:
struct device_error4 { struct device_error4 {
deviceid4 de_deviceid; deviceid4 de_deviceid;
nfsstat4 de_status; nfsstat4 de_status;
nfs_opnum4 de_opnum; nfs_opnum4 de_opnum;
}; };
The ff_ioerr4 structure is used to return error indications for data The ff_ioerr4 structure is used to return error indications for data
files that generated errors during data transfers. These are hints files that generated errors during data transfers. These are hints
to the metadata server that there are problems with that file. For to the metadata server that there are problems with that file. For
each error, ffie_errors.de_deviceid, ffie_offset, and ffie_length each error, ffie_errors.de_deviceid, ffie_offset, and ffie_length
represent the storage device and byte range within the file in which represent the storage device and byte range within the file in which
the error occurred; ffie_errors represents the operation and type of the error occurred; ffie_errors represents the operation and type of
error. The use of device_error4 is described in Section 16.6 of error. The use of device_error4 is described in Section 15.6 of
[NFSv42]. [NFSv42].
9.2. ff_iostats Even though the storage device might be accessed via NFSv3 and
reports back NFSv3 errors to the client, the client is responsible
for mapping these to appropriate NFSv4 status codes as de_status.
Likewise, the NFSv3 operations need to be mapped to equivalent NFSv4
operations.
9.2. Layout Usage Statistics
9.2.1. ff_io_latency4
/// struct ff_io_latency4 {
/// nfstime4 ffil_min;
/// nfstime4 ffil_max;
/// nfstime4 ffil_avg;
/// uint32_t ffil_count;
/// };
///
When determining latencies, the client can collect the minimum via
ffil_min, the maximum via ffil_max, and the average via ffil_avg.
Further, ffil_count relates how many data points were collected in
the reported period.
9.2.2. ff_layoutupdate4
/// struct ff_layoutupdate4 {
/// netaddr4 ffl_addr;
/// nfs_fh4 ffl_fhandle;
/// ff_io_latency4 ffl_read;
/// ff_io_latency4 ffl_write;
/// uint32_t ffl_queue_depth;
/// nfstime4 ffl_duration;
/// bool ffl_local;
/// };
///
ffl_addr differentiates which network address the client connected to
on the storage device. In the case of multipathing, ffl_fhandle
indicates which read-only copy was selected. ffl_read and ffl_write
convey the latencies respectively for both read and write operations.
ffl_queue_depth can be used to indicate how long the I/O had to wait
on internal queues before being serviced. ffl_duration is used to
indicate the time period over which the statistics were collected.
ffl_local if true indicates that the I/O was serviced by the client's
cache. This flag allows the client to inform the metadata server
about "hot" access to a file it would not normally be allowed to
report on.
9.2.3. ff_iostats4
/// struct ff_iostats4 { /// struct ff_iostats4 {
/// offset4 ffis_offset; /// offset4 ffis_offset;
/// length4 ffis_length; /// length4 ffis_length;
/// stateid4 ffis_stateid; /// stateid4 ffis_stateid;
/// uint32_t ffis_duration; /// io_info4 ffis_read;
/// io_info4 ffis_read; /// io_info4 ffis_write;
/// io_info4 ffis_write; /// deviceid4 ffis_deviceid;
/// layoutupdate4 ffis_layoutupdate; /// layoutupdate4 ffis_layoutupdate;
/// }; /// };
/// ///
Recall that [NFSv42] defines io_info4 as: Recall that [NFSv42] defines io_info4 as:
struct io_info4 { struct io_info4 {
uint32_t ii_count; uint32_t ii_count;
uint64_t ii_bytes; uint64_t ii_bytes;
}; };
With pNFS, the data transfers are performed directly between the pNFS With pNFS, the data transfers are performed directly between the pNFS
client and the storage devices. Therefore, the metadata server has client and the storage devices. Therefore, the metadata server has
no visibility to the I/O stream and cannot use any statistical no visibility to the I/O stream and cannot use any statistical
information about client I/O to optimize data storage location. information about client I/O to optimize data storage location.
ff_iostats4 MAY be used by the client to report I/O statistics back ff_iostats4 MAY be used by the client to report I/O statistics back
to the metadata server upon returning the layout. Since it is to the metadata server upon returning the layout. Since it is
infeasible for the client to report every I/O that used the layout, infeasible for the client to report every I/O that used the layout,
the client MAY identify "hot" byte ranges for which to report I/O the client MAY identify "hot" byte ranges for which to report I/O
statistics. The definition and/or configuration mechanism of what is statistics. The definition and/or configuration mechanism of what is
considered "hot" and the size of the reported byte range is out of considered "hot" and the size of the reported byte range is out of
the scope of this document. It is suggested for client the scope of this document. It is suggested for client
implementation to provide reasonable default values and an optional implementation to provide reasonable default values and an optional
run-time management interface to control these parameters. For run-time management interface to control these parameters. For
example, a client can define the default byte range resolution to be example, a client can define the default byte range resolution to be
1 MB in size and the thresholds for reporting to be 1 MB/second or 10 1 MB in size and the thresholds for reporting to be 1 MB/second or 10
I/O operations per second. For each byte range, ffis_offset and I/O operations per second. For each byte range, ffis_offset and
ffis_length represent the starting offset of the range and the range ffis_length represent the starting offset of the range and the range
length in bytes. ffis_duration represents the number of seconds the length in bytes. ffis_read.ii_count, ffis_read.ii_bytes,
reported burst of I/O lasted. ffis_read.ii_count, ffis_write.ii_count, and ffis_write.ii_bytes represent, respectively,
ffis_read.ii_bytes, ffis_write.ii_count, and ffis_write.ii_bytes the number of contiguous read and write I/Os and the respective
represent, respectively, the number of contiguous read and write I/Os aggregate number of bytes transferred within the reported byte range.
and the respective aggregate number of bytes transferred within the
reported byte range. [[AI7: Need to define whether we are using
ffis_layoutupdate or not. --TH]] [[AI8: Actually, ffis_duration
might be what we plop down in there. In any event, ffis_duration
needs some work. --TH]]
9.3. ff_layoutreturn The combination of ffis_deviceid and ffl_addr uniquely identify both
the storage path and the network route to it. Additionally, the
ffis_deviceid informs the metadata server as to the version and/or
minor version being used for I/O to the storage device. Finally, the
ffl_fhandle allows the metadata server to differentiate between
multiple read-only copies of the file on the same storage device.
/// struct ff_layoutreturn { 9.3. ff_layoutreturn4
/// ff_ioerr4 fflr_ioerr_report<>;
/// ff_iostats4 fflr_iostats_report<>; /// struct ff_layoutreturn4 {
/// ff_ioerr4 fflr_ioerr_report<>;
/// ff_iostats4 fflr_iostats_report<>;
/// }; /// };
/// ///
When data file I/O operations fail, fflr_ioerr_report<> is used to When data file I/O operations fail, fflr_ioerr_report<> is used to
report these errors to the metadata server as an array of elements of report these errors to the metadata server as an array of elements of
type ff_ioerr4. Each element in the array represents an error that type ff_ioerr4. Each element in the array represents an error that
occurred on the data file identified by ffie_errors.de_deviceid. If occurred on the data file identified by ffie_errors.de_deviceid. If
no errors are to be reported, the size of the fflr_ioerr_report<> no errors are to be reported, the size of the fflr_ioerr_report<>
array is set to zero. The client MAY also use fflr_iostats_report<> array is set to zero. The client MAY also use fflr_iostats_report<>
to report a list of I/O statistics as an array of elements of type to report a list of I/O statistics as an array of elements of type
ff_iostats4. Each element in the array represents statistics for a ff_iostats4. Each element in the array represents statistics for a
particular byte range. Byte ranges are not guaranteed to be disjoint particular byte range. Byte ranges are not guaranteed to be disjoint
and MAY repeat or intersect. and MAY repeat or intersect.
10. Flexible Files Layout Type LAYOUTERROR 10. Flexible Files Layout Type LAYOUTERROR
If the client is using NFSv4.2 to communicate with the metadata If the client is using NFSv4.2 to communicate with the metadata
server, then instead of waiting for a LAYOUTRETURN to send error server, then instead of waiting for a LAYOUTRETURN to send error
information to the metadata server (see Section 9.1), it can use information to the metadata server (see Section 9.1), it can use
LAYOUTERROR (see Section 16.6 of [NFSv42]) to communicate that LAYOUTERROR (see Section 15.6 of [NFSv42]) to communicate that
information. information. For the Flexible Files Layout Type, this means that
LAYOUTERROR4args is treated the same as ff_ioerr4.
11. Flexible Files Layout Type LAYOUTSTATS 11. Flexible Files Layout Type LAYOUTSTATS
If the client is using NFSv4.2 to communicate with the metadata If the client is using NFSv4.2 to communicate with the metadata
server, then instead of waiting for a LAYOUTRETURN to send I/O server, then instead of waiting for a LAYOUTRETURN to send I/O
statistics to the metadata server (see Section 9.2), it can use statistics to the metadata server (see Section 9.2), it can use
LAYOUTSTATS (see Section 16.7 of [NFSv42]) to communicate that LAYOUTSTATS (see Section 15.7 of [NFSv42]) to communicate that
information. information. For the Flexible Files Layout Type, this means that
LAYOUTSTATS4args.lsa_layoutupdate is overloaded with the same
contents as in ffis_layoutupdate.
12. Flexible File Layout Type Creation Hint 12. Flexible File Layout Type Creation Hint
The layouthint4 type is defined in the [RFC5661] as follows: The layouthint4 type is defined in the [RFC5661] as follows:
struct layouthint4 { struct layouthint4 {
layouttype4 loh_type; layouttype4 loh_type;
opaque loh_body<>; opaque loh_body<>;
}; };
skipping to change at page 21, line 20 skipping to change at page 23, line 14
const RCA4_TYPE_MASK_FF_LAYOUT_MIN = -2; const RCA4_TYPE_MASK_FF_LAYOUT_MIN = -2;
const RCA4_TYPE_MASK_FF_LAYOUT_MAX = -1; const RCA4_TYPE_MASK_FF_LAYOUT_MAX = -1;
[[RFC Editor: please insert assigned constants]] [[RFC Editor: please insert assigned constants]]
struct CB_RECALL_ANY4args { struct CB_RECALL_ANY4args {
uint32_t craa_layouts_to_keep; uint32_t craa_layouts_to_keep;
bitmap4 craa_type_mask; bitmap4 craa_type_mask;
}; };
[[AI13: No, 5661 does not define these above values. The ask here is
to create these and _add_ them to 5661. --TH]]
Typically, CB_RECALL_ANY will be used to recall client state when the Typically, CB_RECALL_ANY will be used to recall client state when the
server needs to reclaim resources. The craa_type_mask bitmap server needs to reclaim resources. The craa_type_mask bitmap
specifies the type of resources that are recalled and the specifies the type of resources that are recalled and the
craa_layouts_to_keep value specifies how many of the recalled craa_layouts_to_keep value specifies how many of the recalled
Flexible File Layouts the client is allowed to keep. The Flexible Flexible File Layouts the client is allowed to keep. The Flexible
File Layout Type mask flags are defined as follows: File Layout Type mask flags are defined as follows:
/// enum ff_cb_recall_any_mask { /// enum ff_cb_recall_any_mask {
/// FF_RCA4_TYPE_MASK_READ = -2, /// FF_RCA4_TYPE_MASK_READ = -2,
/// FF_RCA4_TYPE_MASK_RW = -1 /// FF_RCA4_TYPE_MASK_RW = -1
skipping to change at page 22, line 43 skipping to change at page 24, line 43
permissions or ACL, it SHOULD recall all layouts for that file and it permissions or ACL, it SHOULD recall all layouts for that file and it
MUST fence off the clients holding outstanding layouts for the MUST fence off the clients holding outstanding layouts for the
respective file by implicitly invalidating the outstanding respective file by implicitly invalidating the outstanding
credentials on all data files comprising before committing to the new credentials on all data files comprising before committing to the new
permissions and ACL. Doing this will ensure that clients re- permissions and ACL. Doing this will ensure that clients re-
authorize their layouts according to the modified permissions and ACL authorize their layouts according to the modified permissions and ACL
by requesting new layouts. Recalling the layouts in this case is by requesting new layouts. Recalling the layouts in this case is
courtesy of the server intended to prevent clients from getting an courtesy of the server intended to prevent clients from getting an
error on I/Os done after the client was fenced off. error on I/Os done after the client was fenced off.
15.1. Kerberized File Access
15.1.1. Loosely Coupled
Under this coupling model, the principal used to authenticate the
metadata file is different than that used to authenticate the data
file. I.e., the synthetic principals generated to control access to
the data file could prove to be difficult to manage.
While RPCSEC_GSS version 3 (RPCSEC_GSSv3) [rpcsec_gssv3] could be
used to authorize the client to the storage device on behalf of the
metadata server, such a requirement exceeds the loose coupling model.
I.e., each of the metadata server, storage device, and client would
have to implement RPCSEC_GSSv3.
In all, while either an elaborate schema could be used to
automatically authenticate principals or RPCSEC_GSSv3 aware clients,
metadata server, and storage devices could be deployed, if more
secure authentication is desired, tight coupling should be considered
as described in the next section.
15.1.2. Tightly Coupled
With tight coupling, the principal used to access the metadata file
is exactly the same as used to access the data file. Thus there are
no security issues related to kerberization of a tightly coupled
system.
16. IANA Considerations 16. IANA Considerations
As described in [RFC5661], new layout type numbers have been assigned As described in [RFC5661], new layout type numbers have been assigned
by IANA. This document defines the protocol associated with the by IANA. This document defines the protocol associated with the
existing layout type number, LAYOUT4_FLEX_FILES. existing layout type number, LAYOUT4_FLEX_FILES.
17. References 17. References
17.1. Normative References 17.1. Normative References
[LEGAL] IETF Trust, "Legal Provisions Relating to IETF Documents", [LEGAL] IETF Trust, "Legal Provisions Relating to IETF Documents",
November 2008, <http://trustee.ietf.org/docs/ November 2008, <http://trustee.ietf.org/docs/
IETF-Trust-License-Policy.pdf>. IETF-Trust-License-Policy.pdf>.
[NFSv42] Haynes, T., "NFS Version 4 Minor Version 2", draft-ietf- [NFSv42] Haynes, T., "NFS Version 4 Minor Version 2", draft-ietf-
nfsv4-minorversion2-22 (Work In Progress), April 2014. nfsv4-minorversion2-28 (Work In Progress), November 2014.
[RFC1813] IETF, "NFS Version 3 Protocol Specification", RFC 1813, [RFC1813] IETF, "NFS Version 3 Protocol Specification", RFC 1813,
June 1995. June 1995.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3530] Shepler, S., Callaghan, B., Robinson, D., Thurlow, R., [RFC3530] Shepler, S., Callaghan, B., Robinson, D., Thurlow, R.,
Beame, C., Eisler, M., and D. Noveck, "Network File System Beame, C., Eisler, M., and D. Noveck, "Network File System
(NFS) version 4 Protocol", RFC 3530, April 2003. (NFS) version 4 Protocol", RFC 3530, April 2003.
skipping to change at page 23, line 44 skipping to change at page 26, line 20
"Network File System (NFS) Version 4 Minor Version 1 "Network File System (NFS) Version 4 Minor Version 1
External Data Representation Standard (XDR) Description", External Data Representation Standard (XDR) Description",
RFC 5662, January 2010. RFC 5662, January 2010.
[RFC5664] Halevy, B., Ed., Welch, B., Ed., and J. Zelenka, Ed., [RFC5664] Halevy, B., Ed., Welch, B., Ed., and J. Zelenka, Ed.,
"Object-Based Parallel NFS (pNFS) Operations", RFC 5664, "Object-Based Parallel NFS (pNFS) Operations", RFC 5664,
January 2010. January 2010.
[pNFSLayouts] [pNFSLayouts]
Haynes, T., "Considerations for a New pNFS Layout Type", Haynes, T., "Considerations for a New pNFS Layout Type",
draft-haynes-nfsv4-layout-types-02 (Work In Progress), draft-ietf-nfsv4-layout-types-02 (Work In Progress),
April 2014. October 2014.
17.2. Informative References 17.2. Informative References
[ANSI400-2004] [ANSI400-2004]
Weber, R., Ed., "ANSI INCITS 400-2004, Information Weber, R., Ed., "ANSI INCITS 400-2004, Information
Technology - SCSI Object-Based Storage Device Commands Technology - SCSI Object-Based Storage Device Commands
(OSD)", December 2004. (OSD)", December 2004.
[rpcsec_gssv3]
Adamson, W. and N. Williams, "Remote Procedure Call (RPC)
Security Version 3", November 2014.
Appendix A. Acknowledgments Appendix A. Acknowledgments
Those who provided miscellaneous comments to early drafts of this Those who provided miscellaneous comments to early drafts of this
document include: Matt W. Benjamin, Adam Emerson, Tom Haynes, J. document include: Matt W. Benjamin, Adam Emerson, Tom Haynes, J.
Bruce Fields, and Lev Solomonov. Bruce Fields, and Lev Solomonov.
Appendix B. RFC Editor Notes Appendix B. RFC Editor Notes
[RFC Editor: please remove this section prior to publishing this [RFC Editor: please remove this section prior to publishing this
document as an RFC] document as an RFC]
 End of changes. 41 change blocks. 
100 lines changed or deleted 235 lines changed or added

This html diff was produced by rfcdiff 1.41. The latest version is available from http://tools.ietf.org/tools/rfcdiff/