Kai Schaetzl wrote:

I've replaced disks in a hardware RAID 1 with larger disks and enlarged the array. Now I have to find a way to tell LVM about the extra space. It seems there are two ways:

1. delete partition with fdisk and recreate a larger one. This is

obviously a bit tricky if you do not want to lose data, I haven't investigated further yet. 2. create another partition on the disk, pvcreate another pv and then add it to the existing volume group with vgextend 3. a possible third way: increase the partition size. According to Google most if not all disk tools want to resize a file system as well and since there is no file system they will fail. I'm not sure about the status with this for the tools that come with CentOS (fdisk, parted, other?)

No. 2 seems to be the easy way. Any objections? One I thought of: What does happen when I use No. 2 and I add new lvs? Can it happen that new lvs get "spanned" over both pvs or can I assure that a pv gets created using only one of the pvs? (I would prefer the latter, it doesn't matter if I use a few MB because of the ineffectiveness of allocation.)

Thanks for recommendations.

Kai

Kai,

I ran into the same circumstances a while back and, after a lot of consideration and testing, I chose door #2. It's the most expedient way to do it if you have no other resources available, but it does have some inefficiencies involved in it.

You COULD use option #1, but it requires some additional resources and a LOT of shuffling. Specifically:

- add an extra disk to the volume group (pvcreate, vgextend) - move the extents off of the "old" PVs onto the new PV using pvmove - drop the PVs from the old disks out of the VG - delete the PVs from the old disks - repartitioned the old disks - created PVs on the old disks - added the new/old PVs to the VG - move the extents from the temporary PV to the new/old PVs - remove the temporary disk from the VG, delete the temporary PV

WAY too much shuffling and moving parts to suit me. The system never has to shut down, but performance can truly go into the dumper while pvmove is shuffling bits.

I was originally thinking option #3 would be the "best" (i.e. most efficient) way, but on a test system I tried several times to extend the partitions to include the extra space and failed miserably. Like you, I got stalled at the point of trying to extend the partitions. parted seems to refuse to do so unless there is a supported filesystem on the partition, which does not seem to include LVM.

If anybody has some hints about how to work around parted's reluctance to merely extend an arbitrary partition, I'd really like to know! I know I could use fdisk to delete the old partition and recreated it at a larger size, but that scares the bejesus out of my timid soul, having had power failures during critical operations on more than one occasion.