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Known issues with Linux VOB hosts accessing VOB storage on NAS over NFS

Preventive Service Planning


This technote provides information about known issues with IBM Rational ClearCase VOBs hosted on Linux (both SUSE and Red Hat) accessing VOB database storage over Network File System (NFS).


Various defects in the Linux implementation of the NFS client can cause VOBs to become inaccessible (worst case) or cause significant performance degradations (best case).

The following versions of Linux are known to work correctly (as of June 2012) when VOBs are hosted on a Network Attached Storage (NAS):

  • Red Hat Enterprise 4 Update 8
  • Red Hat Enterprise 5 Update 3
  • Red Hat Enterprise 5 Update 5 with Advisory RHSA-2010:0504-1
  • SUSE 10 with all Updates


OPTION #1: Use one of the Linux versions listed above.

OPTION #2: Do not use NFS to mount the VOB database storage.

Note: This configuration not only side steps potential NFS defects but also improves and optimizes the performance of VOB hosts.

If you choose to avoid using NFS for VOB database storage, consider the following:
    • Split the VOB database storage from the VOB pools and keep the VOB pools on the NAS.

    • Use fiber channel or iSCSI to connect the VOB host to the VOB database storage on the NAS.

OPTION #3: Apply one of the following versions below which introduces a new alternate configuration that involves moving the almd files (used for VOB database concurrency control) to local disk storage on the VOB server to reduce the impact of the known NFS defects on ClearCase. Review technote 1637860: Performance issue with Linux NFS clients when ClearCase VOB database is located on a NAS device for more details on this solution.

Refer to the Rational ClearCase System Requirements List for additional information about supported platforms.

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Document Information

Modified date:
16 June 2018