[CentOS] Re: Proper partition/LVM growth after RAID migration
ssilva at sgvwater.com
Fri Oct 20 16:24:40 UTC 2006
Christian Wahlgren spake the following on 10/19/2006 11:22 PM:
> On 10/18/06, Jay Leafey
> <jay.leafey at mindless.com> wrote:
>> I just finished playing this "game", though with a SAN volume. It
>> took a couple of steps to take advantage of the extra space.
>> First, the SAN manager extended the volume from 100G to 200G. I idled
>> everything referencing the drive by disabling the volume
>> group ( vgchange --available n vgname ). I then ran fdisk against the
>> volume, noting the starting cylinder of the only partition on
>> the drive. I deleted the partition, recreated it using the same
>> starting cylinder and let fdisk figure out the last usable cylinder
>> on the drive, reset the partition type to LVM, and wrote the partition
>> table. At this point I had to reboot to get the system to
>> re-read the partition table. Once it came back up I used pvresize to
>> extend the physical volume to use the additional space in the
>> partition. After that, vgdisplay showed the additional space as
>> available for allocation. This was complicated by the fact that it
>> was actually a two-node cluster (RHCS and GFS) so I had to reboot both
>> nodes before running pvresize.
>> I was originally just going take the easy way out by creating a second
>> partition/physical volume to use the additional space, but it
>> seemed inelegant. I'm unlikely to ever extend this LUN more than
>> once, but you just never know!
> Hi and thanks for letting me know that I'm not the only one with this
> situation. And as it seems there is no straightforward and recommended
> way to do this.
> I have experimented and practiced a little with a CentOS installation
> on VMware to see that both ways of doing this will work. During the
> last couple of days I've been backing up my volume for safety.
> Probably on Sunday I will use my practice and I will post my exact
> Although a bit "raw" I still prefer editing the original partition (as
> described above) than adding extended partitions when you grow you
> "exported disk" (and I most probably will add more disks to my RAID5
> volume in the future). Then you always have a simple and clean
> partition table.
> I also think this scenario should be mentioned in the LVM Howto
> "Common Tasks", and the two (as I know) ways of doing this. Or is this
> scenario very uncommon?
> Regards, Christian
Maybe it was uncommon when the howto was written, but with newer raid
controllers that allow you to expand the array by adding drives, this will
become more common. I also was experimenting in VMWare, and I had a problem
expanding the PV after I expanded the raid partition. But then I was
experimenting by increasing the array with one larger drive at a time, and
letting the array re-sync until I had 3 drives all larger (software raid). I
used fdisk to expand the LVM partition on the raid drive, but couldn't expand
the LV. Maybe I did it wrong, but then thats why I was using vmware.
Next week, I'll go at it again.
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