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HACMP announces support for NFS V4



Document Author:

Michael E Herrera


Document ID:

FLASH10571


Doc. Organization:

Advanced Technical Sales


Document Revised:

04/16/2007


Product(s) covered:

HACMP/ES







Abstract: HACMP announces support for AIX NFSv4 with limitations


HACMP supports AIX NFSv4 with limitations

April 13, 2007

IBM High Availability Cluster Multiprocessing (HACMP*) for AIX 5L*, Version 5.2, V5.3, and V5.4 is expanded to support the use of AIX Network File System Version 4 (NFSv4) on the IBM AIX V5.3 operating system with Technology Level 5 for HACMP clusters.

Note that functional limitations in the current AIX implementation of NFS version 4 impose specific setup and operational requirements in an HACMP cluster. These requirements are detailed below. It is IBM's intention to remove these limitations in a future release. For further information on how to set up an NFS server in an HACMP cluster, refer to the HACMP Installation Guide and the HACMP Administration Guide.

Please refer to the following table for support details.
Note: TL = Technology Level
NFSv4
AIX 5L V5.3

HACMP for AIX 5L,
V5.2
HACMP # IY77919
HACMP # IY77926
AIX TL 5

HACMP for AIX 5L,
V5.3
HACMP # IY78704
HACMP # IY75742
AIX TL 5

HACMP for AIX 5L,
V5.4
HACMP # IY87247
AIX TL 5

AIX NFSv4 limitations with HACMP for AIX 5L

The current AIX NFSv4 server implementation lacks technology to provide comprehensive transfer of NFSv4 file locking state between NFS servers in a HACMP configuration. As a result, NFSv4 client state reclaim operations are not possible after an HACMP fail-over event. Instead clients, rebuild state using non-reclaim type operations.

The potential for errors after an HACMP fail-over exists with applications at NFSv4 clients that perform writes while holding byte range file locks. If the NFS server failure happens during a write operation from an AIX NFSv4 client with a byte range file lock held by that client, the client may fail to successfully recover the locking state and its implied semantic properties with the new server. This occurs if the write at the server made it to the disk and the server failed before generating the response to the NFS client. In this case, applications will receive an ESTALE error return on operations such as write().

The NFSv4 protocol places specific requirements around state management, its recovery aspects, and the implied semantics to applications. The AIX NFSv4 client recovery processes for both state reclaims and state reconstruction take measures to verify the integrity of the recovered state and the associated data correctness. These measures are more rigorous than those used with prior NFS protocol versions.

Service can be obtained from the IBM Electronic Fix Distribution site at:
http://www-03.ibm.com/servers/eserver/support/unixservers/aixfixes.html

For questions or concerns, please send a note to HA Feedback at:
HA Solutions Feedback/Poughkeepsie/IBM or hafeedbk@us.ibm.com



Classification:

Hardware; Software

Category:

Installation and Migration




Platform(s):

IBM System p Family



O/S:

AIX

Keywords:

hacmp, nfs, v4

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