> From: rhelv5-list-bounces@(protected)
> [mailto:rhelv5-list-bounces@(protected)
> Sent: Thursday, February 07, 2008 11:56 PM
>
> In our SAN (IBM DS4800), I can increase the size of a logical drive.
>
> However, I can't figure out how to make RHEL 5.1 see that the
> device has been enlarged. I've tried rescanning the SCSI
> hosts with commands like:
>
> echo "- - -" > /sys/class/scsi_host/host1/scan
> echo "- - -" > /sys/class/scsi_host/host2/scan
>
> (host 1 and 2 are the fibre channel HBAs connected to the san.)
I use:
echo "1" > /sys/bus/scsi/drivers/sd/<h>\:<b>\:<t>\:<l>/block/device/rescan
for all (four, in my case) paths.
After, check /var/log/messages.

> Neither "multipath -F" nor "partprobe /dev/sdi" help, either.
>...
> The above lines resulted in some optimism, however no matter
> what I do, the output of "multipath -l" and "fdisk -l ..."
> still shows the old capacity.
>
> The only thing which seems to work is a reboot, but this is
> not always an option.
>
> How can I make the operating system fully aware of the
> increased capacity of a device?
Unfortunately, it seems that online resizing of a multipath device is
actually impossible:
http://www.redhat.com/archives/dm-devel/2007-August/msg00205.html
(BTW, I think that it is a tremendous limitation for a serious use of Red
Hat in enterprise environment)
Only options are:
- online:
use LVM, create an additional LUN and add it to the VG
- offline:
# Umount filesystem
umount /blabla/...
# Deactivate VG
vgchange -an vg_xxx
multipath -F
multipath -v2
multipath -ll
# Activate VG
vgchange -ay vg_xxx
# Remount filesystem
mount /blabla/...
# Extend PV
pvresize /dev/mapper/<long-multipath-identifier>
# Check VG
vgdisplay -v vg_xxx
# Extend LV
lvextend -l +yyy /dev/vg_xxx/lvol...
# Extend FS
ext2online /dev/vg_xxx/lvol...

If someone has a better option, please explain.
--
Domenico Viggiani

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