HP-UX Logical Volume Manager and MirrorDisk/UX Release Notes HP-UX 11i v3 (March 2012)

Logical Volume Manager and MirrorDisk/UX Release Notes
About this document
This document provides information about the Logical Volume Manager (LVM) and MirrorDisk/UX
products in the March 2012 release of HP-UX 11i v3.
LVM and MirrorDisk/UX overview
Logical Volume Manager (bundle BaseLVM) is the HP-UX default Volume Manager. It provides user
with flexibility in configuring and managing mass storage resources. In HP-UX 11i v3, the LVM
kernel and commands are bundled with the core HP-UX product.
MirrorDisk/UX (bundle B2491BA) is an optionally purchased HP-UX product to enable LVM
mirroring functionality.
Overview of changes
The initial HP-UX 11i v3 release of LVM and MirrorDisk/UX was integrated with the new mass
storage stack, delivering significant performance, scalability, availability, and usability
enhancements. LVM was enhanced to support larger logical volumes, temporary quiescing of
volume groups, and striping with mirroring. Volume group availability was improved: resizing a
LUN and modifying volume group characteristics no longer required the volume group to be
recreated, and replacing a disk could be done online.
This March 2012 of LVM and MirrorDisk/UX provides defect fixes as described in “Fixed issues
in this version” (page 5). In addition, it provides an enhancement to detect half dead disks.
New and changed features in this release
New features
The following LVM feature is new in the March 2012 release of HP-UX 11i v3:
Half Dead Disk Detection
Beginning with the March 2012 release, LVM provides an enhancement to detect half dead disks:
Enhancement CR QXCR1001105226: request to add switch to stop polling PV after number of
retries.
A physical disk that returns media error for write I/Os while allowing read I/Os to succeed (or
vice-versa) is termed a Half Dead Disk. The term also refers to a disk that returns media error for
certain regions while the rest is unaffected. When a disk is fully dead (i.e. both read and write
I/Os to any region of the disk fail), LVM detects it automatically and marks it as unavailable. But
LVM did not handle half dead disk conditions until this release. The half dead disk situation causes
significant performance impact to the system since LVM indefinitely attempts recovery of the affected
physical volumes. The new Half Dead Disk Detection feature can be used to detect and quickly
exclude such PVs from LVM usage.
NOTE: Note that most external storage array disks will have the ability to remap bad blocks
transparently and may not require this feature. Enable this feature only for disks such as internal
disks that can return media errors.
This feature is available only for 2.x version volume groups and can be enabled and fine tuned
using the newly introduced thresholds MediaErrThresCount (pvchange –C) and
MediaErrThresTime (pvchange –T). For more details, refer to the Half Dead Disk Detection
section in the pvchange(1M) man page.
4 Logical Volume Manager and MirrorDisk/UX Release Notes