HP-UX Logical Volume Manager and MirrorDisk/UX Release Notes HP-UX 11i v3 (September 2010)

Severity: Low
Corrective Action: None. You can ignore this message.
After an lvextend failure the deletion of a space-efficient snapshot might cause a panic
Defect ID: QXCR1001030741
Problem: This affects space-efficient snapshots only. In some cases, the deletion
of space-efficient snapshot logical volumes causes a panic. This can
happen after an attempt to increase the size of a logical volume that
has snapshots associated with it. The lvextend command might
fail because no free extents are available in the volume group. If you
create a new snapshot or issue write I/Os that cause data unsharing
on its space-efficient snapshots and then try to delete some
space-efficient snapshot logical volumes, the system panics.
Subsequent activation of the volume group might also panic.
Severity: Critical
Corrective Action: When lvextend fails to increase the size of a logical volume that
has snapshots associated with it because of a lack of free extents in
the volume group, do either of the following:
• Rerun lvextend and choose a smaller logical volume size.
• Add physical volumes to create the necessary free extents in the
volume group and rerun lvextend.
After lvextend completes successfully, you can create snapshots
or issue write I/Os that cause data unsharing or you can delete the
snapshots.
Panic during first snapshot creation for a logical volume while raw I/Os are in progress
Defect ID: QXCR1001040067
Problem: This affects pending raw I/O access to the logical volume for which
a snapshot is being created; it does not affect pending I/Os from a
file system. When creating the first snapshot for a logical volume if
there are pending raw I/Os to this logical volume, the LVM driver
does not wait for all the pending raw I/Os to complete and a panic
occurs. This problem does not occur if all the pending I/Os are from
the file system.
Severity: Critical
Corrective Action: Before creating a snapshot, HP recommends you quiesce the
applications that are issuing raw I/Os to the logical volume.
Automatic increase of pre-allocated extents does not increase by default threshold value for striped
snapshot
Defect ID: QXCR1001042095
Problem: This applies only when no threshold is configured (default threshold
is assumed) and only for striped, space-efficient snapshots. If the
threshold value is set to a value other than default value, LVM chooses
the number of threshold extents (typically 8).
The default threshold value for a striped, space-efficient snapshot
logical volume is reached when the number of free extents is equal
or lesser to 1 full extent worth of stripes. When the threshold is
reached and if automatic increase of pre-allocated extents is enabled,
Known problems and limitations 7