Installation guide

Appendix A. The Device Mapper
80
• mirror
• snapshot and snapshot-origin
• error
• zero
• multipath
• crypt
A.1.1. The linear Mapping Target
A linear mapping target maps a continuous range of blocks onto another block device. The format of a
linear target is as follows:
start length linear device offset
start
starting block in virtual device
length
length of this segment
device
block device, referenced by the device name in the filesystem or by the major and minor numbers
in the format major:minor
offset
starting offset of the mapping on the device
The following example shows a linear target with a starting block in the virtual device of 0, a segment
length of 1638400, a major:minor number pair of 8:2, and a starting offset for the device of 41146992.
0 16384000 linear 8:2 41156992
The following example shows a linear target with the device parameter specified as the device /dev/
hda.
0 20971520 linear /dev/hda 384
A.1.2. The striped Mapping Target
The striped mapping target supports striping across physical devices. It takes as arguments the
number of stripes and the striping chunk size followed by a list of pairs of device name and sector. The
format of a striped target is as follows:
start length striped #stripes chunk_size device1 offset1 ... deviceN offsetN
There is one set of device and offset parameters for each stripe.