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.
Backup Your System
You should always backup your system before attempting a pvmove
operation.
13.5.1. Distributing Old Extents to Existing Disks in Volume Group
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] y
pvmove -- 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.
pvmove is Slow
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.
13.5.1.1. Remove the unused disk
We can now remove the old IDE disk from the volume group.
# vgreduce dev /dev/hdbvgreduce -- 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.
13.5.2. Distributing Old Extents to a New Replacement Disk
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.
13.5.2.1. Prepare the disk
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/sdfpvcreate -- physical volume "/dev/sdf" successfully created
13.5.2.2. Add it to the volume group
As developers use a lot of disk space this is a good volume
group to add it into.
# vgextend dev /dev/sdfvgextend -- INFO: maximum logical volume size is 255.99 Gigabyte
vgextend -- doing automatic backup of volume group "dev"
vgextend -- volume group "dev" successfully extended
13.5.2.3. Move the data
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] y
pvmove -- 249 extents of physical volume "/dev/hdb" successfully moved
13.5.2.4. Remove the unused disk
We can now remove the old IDE disk from the volume group.
# vgreduce dev /dev/hdbvgreduce -- 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.
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