Media Errors; Missing Device When The Volume Group Was Activated; Volume Group Activation Failures; Quorum Problems With A Nonroot Volume Group - HP -UX 11i Administrator's Manual

Media Errors

If an I/O request fails because of a media error, LVM typically prints a message to the console
log file (/var/adm/syslog/syslog.log) when the error occurs. In the event of a media error,
you must replace the disk (see
If your disk hardware supports automatic bad block relocation (usually known as hardware sparing),
enable it, because it minimizes media errors seen by LVM.
NOTE: LVM does not perform software relocation of bad blocks. It recognizes and honors software
relocation entries created by previous releases of LVM but does not create new ones. Enabling or
disabling bad block relocation using lvchange has no effect.

Missing Device When the Volume Group Was Activated

If the device associated with the I/O was not present when the volume group was activated, LVM
prints an error message to the user's terminal at activation time. You must either locate the disk
and restore it to service, or replace it, then activate the volume group again.

Volume Group Activation Failures

Normally, volume groups are automatically activated during system startup. Unless you intentionally
deactivate a volume group using vgchange, you do not need to manually activate volume groups.
In all cases, LVM requires that a quorum of disks in a volume group be available.
A quorum is the required number of physical volumes that must be available in a volume group to
activate that volume group or for it to remain activated. To activate a volume group, more than
half its disks that were available during the last activation must be online and in service. For the
volume group to remain fully operational, at least half the disks must remain present and available.
During run time, when a volume group is already active, if a disk fails or is taken offline, the quorum
might become lost. This condition occurs if less than half of the physical volumes defined for the
volume group now remain fully operational. For example, if two disks belong to a volume group,
the loss of one does not cause a loss of quorum as is the case when activating the volume group.
To lose quorum, both disks must become unavailable. In that case, your volume group remains
active, but a message prints to the console, indicating that the volume group has lost quorum. Until
the quorum is restored (at least one of the LVM disks in the volume group in the previous example
is again available), LVM does not allow you to complete most commands that affect the volume
group configuration. Further, some of the I/O accesses to the logical volumes for that volume group
might hang because the underlying disks are not accessible. Also, until quorum is restored, the
MWC will not be updated because LVM cannot guarantee the consistency (integrity) of the LVM
information.
Use the vgchange -q n option to override the system's quorum check when the volume group
is activated. This option has no effect on the runtime quorum check. Overriding quorum can result
in a volume group with an inaccurate configuration (for example, missing recently creating logical
volumes). This configuration change might not be reversible.
There are ways to override quorum requirements at volume group activation time or boot time.
Even when allowed by LVM, HP recommends that you do not make changes to the LVM configuration
for active volume groups that do not have a quorum of disks present. To correct quorum issues,
HP recommends returning the unavailable disks to service.

Quorum Problems with a Nonroot Volume Group

If you attempt to activate a nonroot volume group when not enough disks are present to establish
a quorum, vgchange displays error messages similar to the following:
# vgchange -a y /dev/vg01
vgchange: Warning: Couldn't attach to the volume group
The path of the physical volume refers to a device that does not exist,
"Disk Troubleshooting and Recovery Procedures" (page
physical volume "/dev/dsk/c1t0d2":
116)).
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