NFSv4 Working Group                                          S. Faibish
Internet-Draft                                          EMC Corporation
Intended status: draft                                       J. Glasgow
Expires: March 28, 2012                                          Google
Updates: 5663                                                  D. Black
Intended Status: Proposed Standard                      EMC Corporation
                                                     September 27, 2011

                         pNFS block disk protection

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   Section 4.e of the Trust Legal Provisions and are provided without
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   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 adds a mechanism to RFC 5663 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. Conclusions....................................................5
   7. References.....................................................5
      7.1. Normative References......................................5
   Authors' Addresses................................................6

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1. Introduction

   Figure 1 shows the overall architecture of a Parallel NFS (pNFS)

          |+-----------+                                 +-----------+
          ||+-----------+                                |           |
          |||           |       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,

   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 to identify pNFS devices. This GPT entry is intended
   for shared storage devices that are accessible to pNFS clients and
   servers, and that may be accessible to other hosts or systems.

2.  Conventions used in this document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   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.  This GUID has been
        generated by one of the draft authors for this purpose.

   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.

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   A pNFS client operating system that supports block layouts SHOULD
   recognize this GUID and 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.

   As of 2011 many current operating system versions support GPT
   including FreeBSD, Linux and Solaris [GPT].

4. Security Considerations

   The pNFS block layout security considerations in [RFC5663] apply to
   this document.

5. IANA Considerations

   There are no IANA considerations in this document.

6. Conclusions

   This document specifies an identification mechanism for pNFS block
   storage devices that can be used to protect those devices during
   operating system boot before the pNFS meta data server can be

7. References

7.1. Normative References


   [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",,
             January 2010.

   This document was prepared using

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Authors' Addresses

   Sorin Faibish (editor)
   EMC Corporation
   228 South Street
   Hopkinton, MA 01748

   Phone: +1 (508) 305-8545

   Jason Glasgow
   5 Cambridge Center, Floors 3-6
   Cambridge, MA  02142

   Phone: +1 (617) 575 1599

   David L. Black
   EMC Corporation
   176 South Street
   Hopkinton, MA 01748

   Phone: +1 (508) 293-7953

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