LVM Volume Group Quiesce/Resume

Recommended practices
Quiesce the volume group when performing a snapshot or a backup of
all the disks in the volume group.
Quiescing the volume group ensures that the LVM metadata and logical volume mirrors are
consistent across all the disks in the volume group prior to performing snapshot(s) of the
disk(s).
Suspend applications and file system activities before quiescing the
volume group.
Although quiescing the volume group ensures that the LVM metadata and logical volume
mirrors are consistent, this does not assure the same for any user application data and file
systems residing in the logical volumes. Although LVM quiesces application I/O as
directed by the quiesce mode, this may not be sufficient to assure the application data is in a
state suitable for the application to be restarted from the backup, if that proves necessary.
Any application and/or file system specific procedures that must be followed to assure the
consistency of the data in the backup image must be completed prior to quiescing the LVM
volume group. This is necessary to assure any updates required to make the application and
file system image consistent are all written to disk and are not queued when the volume
group is quiesced.
Perform a snapshot or backup of every disk in the volume group.
To assure the consistency of the LVM metadata the backup image should contain images
for all the available disks in the volume group when the volume group was quiesced, and all
the disk images should be restored together as well. For instance, if the disks in a volume
group are part of multiple disk arrays, the disks in each array that are part of the volume
group must be snapped and included in the same backup image of the volume group.
Special considerations for I/O performance sensitive applications
When quiescing a volume group, there are special considerations for cluster solutions or
other configurations where response time is monitored. While the volume group is
quiesced application I/O is queued as directed by the quiesce mode specified (until the
volume group is resumed again). If LVM Logical Volume timeouts are used, they are
disabled while the volume group is quiesced. LVM will not time out I/O operations queued
while the volume group is quiesced. When the volume group is resumed, LVM will give
those I/O operations a full time budget as if they were started at that moment.
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