ITEM: AJ8259L

Sysback recreates 4.5Gb disk VG with 8Mb PP size instead of 4Mb

Question:

Env:    AIX 3.2.5, Sysback 3.2, several 4.5Gb disks

Desc:   Customer had a volume group created with several 4.5Gb drives
        with a physical partition (PP) size of 4Mbs.  When restoring a
        Sysback backup of that volume group, the restore process changed
        the PP size 8Mb, and then restored the data.  Why did the PP
        size get changed, and what effect will this have on my data?

Action: There is a supported limit of 1016 PPs per physical volume (PV),
        based on the 127 bytes allocated per physical volume in the
        Volume Group Status Area (VGSA).  Those 127 bytes (or 1016
        bits) are used to maintain information about sync'd or stale
        status of a partition.  4.5Gb drives will naturally exceed
        that supported value, and hence a volume group can be created
        with PVs that have more than 1016 PPs.  Since AIX 3.2.5 was
        release prior to the release of the 4.5Gb drives, there has been
        an enhancement developed to prevent the customer from doing this.

        As seen, Sysback has implemented error checking to change this
        default PP size.  There is NO EFFECT on the data; it will simply
        make each logical volume with 1/2 as many partitions as before,
        each twice as large as before.  This is done before data is even
        restored.

        The APAR to prevent a PV from being configured with more than
        1016 PPs is ix48926, in U437316.

        In addition, the following PTFs are recommended for 4.5Gb support:

        U429283  (Diagnostic support for devices and adapters)
        U429285  (SCSI-2 F/W Support)
        U429287  (SCSI-2 F/W Support for HANFS, IF NEEDED)
        U434006  (SCSI disk and CD-ROM enhancements)
        U434451  (Additional Diagnostic enhancements)
        U435115  (Additional SCSI disk and CD-ROM support)
        U435116  (Latest device drivers, disk and LVM enhancements)
        U435117  (Additional SCSI disk and CD-ROM support)
        U435119  (SMIT screens)
        U435125  (for mksysb and installation)
        U436418  (       "                   )
        U437316  (mkvg allows for more than 1016 PPs)
        U436971  (prevents creating VGs that exceed 1016 PP/PV limit)
        U437507  (Additional Diag Support; formatting drives)



Support Line: Sysback recreates 4.5Gb disk VG with 8Mb PP size instead of 4Mb ITEM: AJ8259L

Dated: May 1995 Category: N/A

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