HP-UX Logical Volume Manager and MirrorDisk/UX Release Notes HP-UX 11i v3 (March 2011)

Limitations
This section provides a list of limitations as known to HP at time of publication.
• Logical volumes that have snapshots associated with them might experience an increase in
latencies associated with writes. This is also applicable for writes on (writable) snapshots
themselves.
• With the HP-UX 11i v3 September 2010 Update release, when the number of extents remaining
in a space-efficient snapshot logical volume’s pre-allocated pool falls beyond a certain internally
computed threshold, by default, LVM tries to increase the pre-allocated pool size by threshold
value. This does not guarantee that snapshot will not become over-commit. For example, if
the I/O rate is faster than auto pre-allocation, the snapshot becomes over-commit.
If auto pre-allocation is manually disabled, a message is logged in the syslog. This message
is displayed to inform you that further unsharing of data between the snapshot and its successors
might end up depleting the extents in the pre-allocated pool and lead to the snapshot and its
predecessors being marked as inoperative. As soon as you see this message in the syslog,
you must increase the pre-allocated extent pool size for the snapshot logical volume.
• For more limitations on snapshots, see the Using LVM Logical Volume Snapshots white paper.
Installation requirements
This section describes the installation requirements for this release.
Required hardware
LVM and MirrorDisk/UX have no hardware requirements beyond the requirements of the HP-UX
11i v3 operating system. Both products run on all supported HP 9000 and HP Integrity servers.
Required software
Because LVM is installed with the HP-UX 11i v3 operating environment, there are no software
requirements beyond the requirements of the HP-UX 11i v3 operating system. MirrorDisk/UX
requires the BaseLVM™ product.
Required patches
In HP-UX 11i v3, LVM and MirrorDisk/UX do not require any software patches.
For each of the following subsystems, you can download patches from the following website:
http://www2.itrc.hp.com/service/patch/mainPage.do
Mass Storage Critical Resource Analysis
The Mass Storage Critical Resource Analysis (MS CRA) tool checks for a maximum of two mirror
copies of a logical volume. However, Version 2.0 and higher volume groups allow up to five mirror
copies. To enable MS CRA to check for a maximum of five mirror copies of a volume, you must
install the following patch, or a superseding patch:
• PHCO_37562
MS CRA checks for a maximum of 511 physical volumes in a volume group. However, Version
2.1 volume groups allow up to 2048 physical volumes. To enable MS CRA to check for a maximum
of 2048 physical volumes in a volume group, you must install the following patch:
• PHCO_38145
PHCO_38145 supersedes PHCO_37562. Installing PHCO_38145 enables both checks.
10 Logical Volume Manager and MirrorDisk/UX Release Notes