[ Previous | Next | Contents | Glossary | Home | Search ]
AIX Version 4.3 System Management Guide: Operating System and Devices

Logical Volume Manager Limitation Warnings

  1. The user tries to use mkvg to create a volume group and the number of physical partitions on a disk in the volume group exceeds 1016.

    The workaround to this limitation is to select from the physical partition size ranges of:

    1, 2, (4), 8, 16, 32, 64, 128, 256
    Megabytes and use the mkvg -s option.

  2. The disk that violates the 1016 limitation attempts to join a pre-existing volume group with the extendvg command. The user can recreate the volume group with a larger partition size allowing the new disk to work or create a standalone volume group consisting of a larger physical size for the new disk.

    If the install code detects that the rootvg drive is larger than 4GB, it will change the mkvg -s value until the entire disk capacity can be mapped to the available 1016 tracks. This install change also implies that all other disks added to rootvg, regardless of size, will also be defined at that physical partition size.

    For RAID systems, the /dev/hdiskX name used by LVM in AIX may really consist of many non-4GB disks. In this case, the 1016 requirement still exists. LVM is unaware of the size of the individual disks that may really make up /dev/hdiskX. LVM bases the 1016 limitation on the AIX recognized size of /dev/hdiskX, and not the real physical disks that make up /dev/hdiskX.


    1016 VGSA Regulations The 1016 VGSA is used to track the staleness of mirrors. The staleness of mirrors indicates that one copy of the data will not look like the other two copies. If you are in volation of 1016, you may get a false report of a non-mirrored logical volume being stale, or you may get a false indication that one of your mirror copies has gone stale. Also, the migratepv command may fail because migratepv briefly uses mirroring to move a logical volume from one disk to another. If the target logical partition is incorrectly considered stale, the migratepv cannot remove the source logical partition, and the command will fail in the middle of migration. The reorgvg is another command that performs its actions by using temporary mirroring.
    Mirroring or migratepv If you do not use mirroring or the migratepv command, your data is still safe as the day before you found out about 1016 violations. The data may be lost only if you are mirroring a logical volume, and:
    • All copies go bad at the same time, and
    • LVM is not aware of it because copies that go bad are beyond the 1016 tracking range.

    In this case, you would still lose data if you were within the 1016 range. If you do not use mirror or the migratepv command, this issue would not be a problem.

    Move Volume Group A volume group can be moved between systems and versions of AIX. The enforcement of this 1016 limit is only during mkvg and extendvg. The data is safe on all versions of AIX.
    Change the PP Size Limitation The PP size limitation will not be changed. The ability to change the PP size assures that regardless of the size of your disk drive, you will be able to accommodate the drive below 1016 limit. Also, if a change to the limitation is made, then a huge incompatibility would occur in the LVM.
    Rebuild the Volume Group The later versions of AIX mentioned in this document only prevent the future creation of disks in volume groups that will violate the 1016 limitation. Disks that already violate the 1016 limit must be recreated at larger PP sizes.

[ Previous | Next | Contents | Glossary | Home | Search ]