[aklug] Re: adding disks to a volset.

On Mon, 19 Apr 2010, Thomison, Lee wrote:

> $ df -lh
> Filesystem Size Used Avail Use% Mounted on
> /dev/mapper/VolGroup00-LogVol01
> 7.6G 3.5G 3.8G 49% /
> /dev/sda1 99M 25M 69M 27% /boot
> tmpfs 2.0G 0 2.0G 0% /dev/shm
> /dev/mapper/VolGroup00-LogVol07
> 1.9G 1.8G 0 100% /home
> /dev/mapper/VolGroup00-LogVol08
> 1.9G 946M 878M 52% /opt/oracle
> /dev/mapper/VolGroup00-LogVol06
> 961M 20M 892M 3% /tmp
> /dev/mapper/VolGroup00-LogVol05
> 4.8G 628M 3.9G 14% /var
> /dev/mapper/VolGroup00-LogVol02

I don't think you need to do either one. Look at your disk utilization
above. Unless you built that RAID5 with very small disks, odds are you have
a lot of unallocated space as it is. Run the 'vgs' command. One one of
my servers the output looks like the following:

   VG #PV #LV #SN Attr VSize VFree
   datavg 1 3 0 wz--n- 300.00G 100.00G
   rootvg 1 7 0 wz--n- 68.23G 36.68G

Note the VFree column. If you have any significant space there you'll just
use the 'lvextend' command to allocate it to your LV. Grow the filesystem,
and you're done.

Now, if you are out of space in the original array you have a couple of
options. Option #1 that you mentioned is the easiest. However, your
hardware may support resizing the RAID5 array, which will give you more
usable space out of the new drives, and something you may want to consider
if the new drives are closely matched to the original drives and write
performance isn't a problem. That's a much more complicated, however, and
will require some downtime to resize the the PV before the space becomes
visible to the VG.

Option #2 removes much of the benefit of running LVM in the first place.
Avoid that option if possible.

         --Arthur Corliss
           Live Free or Die
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Received on Tue Apr 20 10:28:27 2010