3.6. Tying it all together
A concrete example will help:
Lets suppose we have a volume group called VG1, this volume group
has a physical extent size of 4MB. Into this volume group we
introduce 2 hard disk partitions, /dev/hda1 and /dev/hdb1. These
partitions will become physical volumes PV1 and PV2 (more
meaningful names can be given at the administrators discretion).
The PV's are divided up into 4MB chunks, since this is the extent
size for the volume group. The disks are different sizes and we
get 99 extents in PV1 and 248 extents in PV2. We now can create
ourselves a logical volume, this can be any size between 1 and 347
(248 + 99) extents. When the logical volume is created a mapping
is defined between logical extents and physical extents, eg.
logical extent 1 could map onto physical extent 51 of PV1, data
written to the first 4 MB of the logical volume in fact be written
to the 51st extent of PV1.