View source for How to Remove a Drive from LVM

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A hard drives can be removed from your Amahi HDA for replacement or to reduce storage space.

We'll detail how to remove such hard drives.

=Important Notes=

* This is an '''advanced''' how-to on how to remove drives from your HDA.
* Amahi cannot be held responsible for any data breakage or destruction arising from the use or misuse of this script. We provide it as a service in good will. You accept this automatically if you use the script.
* This was copied from the LVM project at http://tldp.org/HOWTO/LVM-HOWTO/removeadisk.html

=Step by step instructions=
==Removing an Old Disk==

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.

=='''Caution Backup Your System'''==
 	

You should always backup your system before attempting a pvmove operation.


==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


<div style="border: 1px solid #A3B1BF; padding: .5em 1em; color: #000; background-color: #E6F2FF; margin: 3px 3px 1em 3px;">pvmove /dev/hdb
pvmove -- 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
</div>    

This will move the allocated physical extents from /dev/hdb onto the rest of the disks in the volume group.

Note	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.
==Remove the unused disk==

We can now remove the old IDE disk from the volume group.


<div style="border: 1px solid #A3B1BF; padding: .5em 1em; color: #000; background-color: #E6F2FF; margin: 3px 3px 1em 3px;"> vgreduce dev /dev/hdb
vgreduce -- doing automatic backup of volume group "dev"
vgreduce -- volume group "dev" successfully reduced by physical volume:
vgreduce -- /dev/hdb
</div>          

The drive can now be either physically removed when the machine is next powered down or reallocated to other users.
==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.
==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.


<div style="border: 1px solid #A3B1BF; padding: .5em 1em; color: #000; background-color: #E6F2FF; margin: 3px 3px 1em 3px;"> pvcreate /dev/sdf
pvcreate -- physical volume "/dev/sdf" successfully created
</div>            

==Add it to the volume group==

As developers use a lot of disk space this is a good volume group to add it into.


<div style="border: 1px solid #A3B1BF; padding: .5em 1em; color: #000; background-color: #E6F2FF; margin: 3px 3px 1em 3px;"> 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
</div>

==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.


<div style="border: 1px solid #A3B1BF; padding: .5em 1em; color: #000; background-color: #E6F2FF; margin: 3px 3px 1em 3px;"> pvmove /dev/hdb /dev/sdf
pvmove -- 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
</div>

==Remove the unused disk==

We can now remove the old IDE disk from the volume group.


<div style="border: 1px solid #A3B1BF; padding: .5em 1em; color: #000; background-color: #E6F2FF; margin: 3px 3px 1em 3px;"> vgreduce dev /dev/hdb
vgreduce -- doing automatic backup of volume group "dev"
vgreduce -- volume group "dev" successfully reduced by physical volume:
vgreduce -- /dev/hdb
</div>

The drive can now be either physically removed when the machine is next powered down or reallocated to some other users.

If you need to add a disk please go to [[Adding a second hard drive to your HDA]]