Internet DRAFT - draft-faibish-nfsv4-pnfs-block-disk-protection


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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   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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