Parallel NFS (pNFS) Flexible File Layout
RFC 8435
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Type |
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RFC - Proposed Standard
(August 2018; No errata)
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Last updated |
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2018-08-24
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IETF
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plain text
pdf
htmlized
bibtex
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Reviews |
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WG state
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Submitted to IESG for Publication
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Document shepherd |
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Spencer Shepler
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Shepherd write-up |
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Show
(last changed 2017-10-25)
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| IESG |
IESG state |
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RFC 8435 (Proposed Standard)
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Consensus Boilerplate |
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Yes
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Telechat date |
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Responsible AD |
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Spencer Dawkins
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Send notices to |
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Spencer Shepler <spencer.shepler@gmail.com>
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| IANA |
IANA review state |
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Version Changed - Review Needed
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IANA action state |
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RFC-Ed-Ack
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Internet Engineering Task Force (IETF) B. Halevy
Request for Comments: 8435
Category: Standards Track T. Haynes
ISSN: 2070-1721 Hammerspace
August 2018
Parallel NFS (pNFS) Flexible File Layout
Abstract
Parallel NFS (pNFS) allows a separation between the metadata (onto a
metadata server) and data (onto a storage device) for a file. The
flexible file layout type is defined in this document as an extension
to pNFS that allows the use of storage devices that require only a
limited degree of interaction with the metadata server and use
already-existing protocols. Client-side mirroring is also added to
provide replication of files.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc8435.
Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Halevy & Haynes Standards Track [Page 1]
RFC 8435 pNFS Flexible File Layout August 2018
Table of Contents
1. Introduction ....................................................3
1.1. Definitions ................................................4
1.2. Requirements Language ......................................6
2. Coupling of Storage Devices .....................................6
2.1. LAYOUTCOMMIT ...............................................7
2.2. Fencing Clients from the Storage Device ....................7
2.2.1. Implementation Notes for Synthetic uids/gids ........8
2.2.2. Example of Using Synthetic uids/gids ................9
2.3. State and Locking Models ..................................10
2.3.1. Loosely Coupled Locking Model ......................11
2.3.2. Tightly Coupled Locking Model ......................12
3. XDR Description of the Flexible File Layout Type ...............13
3.1. Code Components Licensing Notice ..........................14
4. Device Addressing and Discovery ................................16
4.1. ff_device_addr4 ...........................................16
4.2. Storage Device Multipathing ...............................17
5. Flexible File Layout Type ......................................18
5.1. ff_layout4 ................................................19
5.1.1. Error Codes from LAYOUTGET .........................23
5.1.2. Client Interactions with FF_FLAGS_NO_IO_THRU_MDS ...23
5.2. LAYOUTCOMMIT ..............................................24
5.3. Interactions between Devices and Layouts ..................24
5.4. Handling Version Errors ...................................24
6. Striping via Sparse Mapping ....................................25
7. Recovering from Client I/O Errors ..............................25
8. Mirroring ......................................................26
8.1. Selecting a Mirror ........................................26
8.2. Writing to Mirrors ........................................27
8.2.1. Single Storage Device Updates Mirrors ..............27
8.2.2. Client Updates All Mirrors .........................27
8.2.3. Handling Write Errors ..............................28
8.2.4. Handling Write COMMITs .............................28
8.3. Metadata Server Resilvering of the File ...................29
9. Flexible File Layout Type Return ...............................29
9.1. I/O Error Reporting .......................................30
9.1.1. ff_ioerr4 ..........................................30
9.2. Layout Usage Statistics ...................................31
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