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 HP-UX Logical Volume Manager and MirrorDisk/UX Release Notes: HP-UX 11i v3 March 2008 (B.11.31) > Logical Volume Manager and MirrorDisk/UX Release Notes

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This release is specific for HP-UX 11i v3 (B.11.31). The following compatibility issues exist in the March 2008 release of HP-UX 11i v3.

Version 2.0 Volume Groups

  • Version 2.0 volume groups are not recognized on previous releases of HP-UX, including previous versions of HP-UX 11i v3. Version 1.0 volume groups are supported on all supported versions of HP-UX, including 11i v1, 11i v2, and 11i v3.

  • There is currently no method for converting a volume group in place from one version to another. To migrate a Version 1.0 volume group to Version 2.0, you must create a new Version 2.0 volume group and copy the data.

  • The following HP-UX products do not currently support Version 2.0 volume groups:

    • HP Process Resource Manager (HP PRM)

    • Encrypted Volume and File System (EVFS v1.0)

    These products plan to add support of Version 2.0 volume groups. For the most recent information on these products, see the IT Resource Center (ITRC) at http://itrc.hp.com, or consult the release notes for the specific product.

Moving from HP-UX 11i v2 to HP-UX 11i v3

If you are migrating a system from HP-UX 11i v2 to HP-UX 11i v3, please refer to the LVM migration white paper described in the “Related Documentation” section. It contains information on migrating an LVM configuration from the legacy naming model to the agile naming model.

Existing LVM configurations created on HP-UX 11i v2 continue to work on HP-UX 11i v3 under the legacy naming model. However, there is a change in behavior:

  • Alternate Links (PVLinks): In HP-UX 11i v3, management of multi-pathed devices is available outside of LVM using the next generation mass storage stack. By default, the next generation mass storage stack distributes I/O requests across all available paths to a multi-pathed disk, even when using legacy device special files. Using LVM with persistent or legacy device special files may cause I/O requests to be sent across alternate links, even if the links are not configured as PVLinks; this should not introduce any errors, but it does differ from PVLink behavior in previous releases.

    HP recommends converting volume groups with multi-pathed disks to persistent device special files and native multi-pathing, as described in the migration white paper in “Related Documentation”.

    However, if you want backward-compatible PVLink behavior, you must use legacy device special files for physical volumes, and disable the mass storage stack multi-pathing for those physical volumes. To disable multi-pathing on legacy device special files, use the scsimgr command to configure a global device tunable called leg_mpath_enable.

    For each multi-pathed disk, enter the following command:

    # scsimgr save_attr -D /dev/rdisk/diskn -a leg_mpath_enable=false

    Alternatively, you can disable multi-pathing for all legacy device files with this command:

    # scsimgr save_attr -a leg_mpath_enable=false

    Note that this has no effect on multi-pathing through persistent device special files. For more information, see scsimgr(1M).

Moving Volume Groups from HP-UX 11i v3 to Previous HP-UX Releases

If a volume group used on HP-UX 11i v3 is accessed from a system running a previous release of HP-UX 11i, you may encounter these compatibility issues:

  • Version 2.0 volume groups: As noted in “Version 2.0 Volume Groups”, Version 2.0 volume groups are not recognized on previous releases of HP-UX.

  • Logical volumes larger than 2 TB: Releases prior to HP-UX 11i v3 can only access data within the first 2 TB of a logical volume. If a logical volume larger than 2 TB is created on HP-UX 11i v3, its use is not recommended on any previous HP-UX release. The volume group can be activated and the logical volume can be used, but any data in that logical volume beyond 2 TB will be inaccessible.

    NOTE: Patches PHKL_36745 and PHCO_36746 resolve this compatibility issue for HP-UX 11i v2. Installing these patches enables the creation and use of logical volumes up to 16 TB.

  • Striped Mirrors: Releases prior to HP-UX 11i v3 only support extent-based striping via the -D option to lvcreate. If a logical volume using simultaneous mirroring and non-extent-based striping is created on HP-UX 11i v3, attempts to import or activate its associated volume group will fail on a previous HP-UX release. To import the volume group, you must remove the incompatible logical volumes or reduce them to a single mirror.

    NOTE: Patches PHKL_36745 and PHCO_36746 resolve this compatibility issue for HP-UX 11i v2. Installing these patches enables the creation and use of striped mirrors.

  • Mirror Write Cache (MWC): When a volume group containing a logical volume using the Mirror Write Cache is activated on HP-UX 11i v3, its Mirror Write Cache format is converted to a new format. Importing or activating the volume group on a previous HP-UX release does not recognize the new format and triggers a full resynchronization of the mirrors.

    NOTE: PHKL_36244 adds support for the new MWC format to HP-UX 11i v2. Installing that patch avoids the unnecessary resynchronization.


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