Say you have an old IDE drive on /dev/hdb. You want to remove that old disk but a lot of files are on it.
You should always backup your system before attempting a pvmove operation.
If you have enough free extents on the other disks in the volume group, you have it easy. Simply run
# pvmove /dev/hdbpvmove -- moving physical extents in active volume group "dev" pvmove -- WARNING: moving of active logical volumes may cause data loss!pvmove -- do you want to continue? [y/n]ypvmove -- 249 extents of physical volume "/dev/hdb" successfully moved
This will move the allocated physical extents from /dev/hdb onto the rest of the disks in the volume group.
Be aware that pvmove is quite slow as it has to copy the
contents of a disk block by block to one or more disks. If you
want more steady status reports from pvmove, use the
-v flag.
We can now remove the old IDE disk from the volume group.
# vgreduce dev /dev/hdb
vgreduce -- doing automatic backup of volume group "dev"
vgreduce -- volume group "dev" successfully reduced by physical volume:
vgreduce -- /dev/hdb
The drive can now be either physically removed when the machine is next powered down or reallocated to other users.
If you do not have enough free physical extents to distribute the old physical extents to, you will have to add a disk to the volume group and move the extents to it.
First, you need to pvcreate the new disk to make it available to LVM. In this recipe we show that you don't need to partition a disk to be able to use it.
# pvcreate /dev/sdf
pvcreate -- physical volume "/dev/sdf" successfully created
As developers use a lot of disk space this is a good volume group to add it into.
# vgextend dev /dev/sdf
vgextend -- INFO: maximum logical volume size is 255.99 Gigabyte
vgextend -- doing automatic backup of volume group "dev"
vgextend -- volume group "dev" successfully extended
Next we move the data from the old disk onto the new one. Note that it is not necessary to unmount the file system before doing this. Although it is *highly* recommended that you do a full backup before attempting this operation in case of a power outage or some other problem that may interrupt it. The pvmove command can take a considerable amount of time to complete and it also exacts a performance hit on the two volumes so, although it isn't necessary, it is advisable to do this when the volumes are not too busy.
# pvmove /dev/hdb /dev/sdfpvmove -- moving physical extents in active volume group "dev" pvmove -- WARNING: moving of active logical volumes may cause data loss!pvmove -- do you want to continue? [y/n]ypvmove -- 249 extents of physical volume "/dev/hdb" successfully moved
We can now remove the old IDE disk from the volume group.
# vgreduce dev /dev/hdb
vgreduce -- doing automatic backup of volume group "dev"
vgreduce -- volume group "dev" successfully reduced by physical volume:
vgreduce -- /dev/hdb
The drive can now be either physically removed when the machine is next powered down or reallocated to some other users.