Installation guide

The snapshot and snapshot-origin Mapping Targets
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logargs
the log arguments for the mirror; the number of log arguments provided is specified by the #log-
args parameter and the valid log arguments are determined by the log_type parameter.
#devs
the number of legs in the mirror; a device and an offset is specified for each leg
device
block device for each mirror leg, referenced by the device name in the filesystem or by the major
and minor numbers in the format major:minor. A block device and offset is specified for each
mirror leg, as indicated by the #devs parameter.
offset
starting offset of the mapping on the device. A block device and offset is specified for each mirror
leg, as indicated by the #devs parameter.
The following example shows a mirror mapping target for a clustered mirror with a mirror log kept on
disk.
0 52428800 mirror clustered_disk 4 253:2 1024 UUID block_on_error 3 253:3 0 253:4 0 253:5 0
0
starting block in virtual device
52428800
length of this segment
mirror clustered_disk
mirror target with a log type specifying that mirror is clustered and the mirror log is maintained on
disk
4
4 mirror log arguments will follow
253:2
major:minor numbers of log device
1024
region size the mirror log uses to keep track of what is in sync
UUID
UUID of mirror log device to maintain log information throughout a cluster
block_on_error
mirror should respond to errors
3
number of legs in mirror
253:3 0 253:4 0 253:5 0
major:minor numbers and offset for devices constituting each leg of mirror
A.1.4. The snapshot and snapshot-origin Mapping Targets
When you create the first LVM snapshot of a volume, four Device Mapper devices are used: