Internet DRAFT - draft-ietf-nfsv4-pnfs-block-disk-protection
draft-ietf-nfsv4-pnfs-block-disk-protection
NFSv4 Working Group D. Black (ed.)
Internet-Draft EMC Corporation
Intended status: Proposed Standard J. Glasgow
Expires: December YY, 2012 Google
Updates: 5663 S. Faibish
EMC Corporation
June 22, 2012
pNFS block disk protection
draft-ietf-nfsv4-pnfs-block-disk-protection-03
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Abstract
Parallel NFS (pNFS) extends Network File System version 4 (NFSv4) to
enable direct client access to file data on storage, bypassing the
NFSv4 server. This can increase both performance and parallelism,
but requires additional client functionality, some of which depends
upon the type of storage used. The pNFS specification for block
storage (RFC 5663) describes how clients can identify the volumes
used for pNFS, but this mechanism requires communication with the
NFSv4 server. This document updates RFC 5663 to add a mechanism that
enables identification of block storage devices used by pNFS file
systems without communicating with the server. This enables clients
to control access to pNFS block devices when the client initially
boots, as opposed to waiting until the client can communicate with
the NFSv4 server.
Table of Contents
1. Introduction...................................................3
2. Conventions used in this document..............................4
3. GPT Partition Table Entry......................................4
4. Security Considerations........................................5
5. IANA Considerations............................................5
6. References.....................................................6
6.1. Normative References......................................6
6.2. Informative References....................................6
Acknowledgements..................................................6
Authors' Addresses................................................7
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1. Introduction
Figure 1 shows the overall architecture of a Parallel NFS (pNFS)
system:
+-----------+
|+-----------+ +-----------+
||+-----------+ | |
||| | NFSv4.1 + pNFS | |
+|| Clients |<------------------------------>| MDS |
+| | | |
+-----------+ | |
||| +-----------+
||| |
||| |
||| Storage +-----------+ |
||| Protocol |+-----------+ |
||+----------------||+-----------+ Control |
|+-----------------||| | Protocol |
+------------------+|| Storage |------------+
+| Devices |
+-----------+
Figure 1 pNFS Architecture
In this document, "storage device" is used as a general term for a
data server and/or storage server for any pNFS layout type. The
MetaData Server (MDS) is the NFSv4 server that provides pNFS layouts
to clients and handles operations on file metadata (e.g., names,
attributes).
For the pNFS block protocol as specified in [RFC5663], client
identification of pNFS storage devices requires contacting the MDS to
obtain device signature information. It is not possible for a pNFS
client to reliably identify pNFS block storage devices without
contacting the MDS because the device signature location and contents
may vary among devices and servers; both device signature location
and contents are determined by the MDS, not the client.
Typical operating system (OS) boot functionality scans and activates
block devices (e.g., SCSI) before activating the NFS client
(including pNFS functionality). That sequence of operations creates
a window of time during which the client OS may modify a pNFS block
device without contacting the server (e.g., by attempting to mount or
initialize a local physical filesystem). This document specifies an
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identification mechanism for pNFS block storage devices that can be
used by an OS implementation to remove this window of vulnerability.
Many storage area network (SAN) storage systems provide quasi-static
access control mechanisms (e.g., Logical Unit Number (LUN) mapping
and/or masking) that operate at the granularity of individual hosts.
While it is feasible to use such mechanisms to remove this window
(e.g., by only enabling a client to access pNFS block storage devices
after the client has contacted the responsible MDS), that usage is
undesirable and potentially problematic. This is because the storage
access control mechanisms are quasi-static; they are typically
configured once to allow client access to the block pNFS storage
devices and not reconfigured dynamically (e.g., based on crashes and
reboots). Block storage access controls can be changed to respond to
unusual circumstances (e.g., to fence [remove access from] an
uncooperative pNFS client), but should not be used as part of routine
client operations (e.g., reboot). A different mechanism is needed.
This document specifies an entry in the GUID partition table (GPT)
that can be used by a pNFS server to label pNFS storage devices. This
GPT entry is intended for shared pNFS storage devices that are
accessible to pNFS clients and servers, and that may be accessible to
other hosts or systems. This entry enables pNFS clients as well as
other hosts and systems to avoid accessing pNFS storage devices via
means other than pNFS.
2. Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC-2119 [RFC2119].
3. GPT Partition Table Entry
The following mechanism enables pNFS clients to identify pNFS block
storage devices without contacting the server:
- Each block storage device dedicated to pNFS includes a GUID
partition table (GPT) [GPT].
- The pNFS Block Storage partitions are identified in the GPT with
GUID e5b72a69-23e5-4b4d-b176-16532674fc34 which has been
generated for this purpose. GPT GUID usage is well understood
and implemented. This document provides a definition for this
GUID and its usage. A central registration mechanism does not
exist for GPT GUIDs, or GUIDs in general by design, see
[RFC4122].
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This mechanism enables an operating system to prevent non-pNFS access
to pNFS block storage immediately upon boot. Servers that support
pNFS block layouts SHOULD use the GPT and this GUID for all pNFS
block storage devices.
A pNFS client operating system that supports block layouts SHOULD
recognize this GUID and SHOULD use its presence to prevent data
access to pNFS block devices until a layout that includes the device
is received from the MDS.
Data stored on pNFS block layout storage devices can be better
protected by incorporating checks for this GUID into other hosts and
systems that do not support pNFS block layouts. If pNFS block
storage devices are presented to such hosts or systems by mistake,
the check for presence of this GUID can be used to prevent writes
that could otherwise corrupt stored pNFS data.
Many current operating system versions support the GPT [GPT-W].
4. Security Considerations
The pNFS block layout security considerations in [RFC5663] apply to
this document.
The security considerations in [RFC4122] apply to the GUID specified
in this document.
5. IANA Considerations
There are no IANA considerations in this document.
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6. References
6.1. Normative References
[GPT] Unified EFI Forum, "Unified Extensible Firmware Interface
Specification", Version 2.3.1, Errata A, Section 5.3,
September 2011, available from http://www.uefi.org .
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC5663] Black, D., Glasgow, J., Fridella, S., "Parallel NFS (pNFS)
Block/Volume Layout", RFC 5663, January 2010.
6.2. Informative References
[GPT-W] http://en.wikipedia.org/wiki/GUID_Partition_Table
[RFC4122] Leach, P., Mealling, M., Salz, R., "A Universally Unique
IDentifier (UUID) URN Namespace", RFC 4122, July 2005.
Acknowledgements
This document was produced by the IETF NFSv4 Working Group. Review
comments from members of the working group improved this document and
are gratefully acknowledged. The authors would like to thank Tom
Talpey, and members of the IESG for helpful comments on this
document, and also Alex Burlyga for providing an appropriate
reference for the format of the GPT.
This document was prepared using 2-Word-v2.0.template.dot.
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Authors' Addresses
David L. Black (editor)
EMC Corporation
176 South Street
Hopkinton, MA 01748
US
Phone: +1 (508) 293-7953
Email: david.black@emc.com
Jason Glasgow
Google
5 Cambridge Center, Floors 3-6
Cambridge, MA 02142
US
Phone: +1 (617) 575-1599
Email: jglasgow@google.com
Sorin Faibish
EMC Corporation
228 South Street
Hopkinton, MA 01748
US
Phone: +1 (508) 305-8545
Email: sfaibish@emc.com
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