topic Re: Replacing Failed disk in Operating System - HP-UX

Replacing Failed disk

Madhu_17 — Thu, 04 Nov 2004 08:07:13 GMT

Hi Gurus,

I want to replace a failed disk.

Can you pls provide me detailed step by step of tasks to be performed before the disk replacement and after the disk is inserted, as i'm a beginner in HP-UX.

Pls find the output of the current status.

DSLARCM1:/home/root> lvdisplay -v /dev/vg04/lvol1|grep -i stale
LV Status available/stale
0000 /dev/dsk/c0t4d0 0000 stale /dev/dsk/c3t2d0 0000 current
0001 /dev/dsk/c0t4d0 0001 stale /dev/dsk/c3t2d0 0001 current
0002 /dev/dsk/c0t4d0 0002 stale /dev/dsk/c3t2d0 0002 current
0003 /dev/dsk/c0t4d0 0003 stale /dev/dsk/c3t2d0 0003 current
0005 /dev/dsk/c0t4d0 0005 stale /dev/dsk/c3t2d0 0005 current
0006 /dev/dsk/c0t4d0 0006 stale /dev/dsk/c3t2d0 0006 current
0007 /dev/dsk/c0t4d0 0007 stale /dev/dsk/c3t2d0 0007 current
0496 /dev/dsk/c0t4d0 0496 stale /dev/dsk/c3t2d0 0496 current
0504 /dev/dsk/c0t4d0 0504 stale /dev/dsk/c3t2d0 0504 current
0505 /dev/dsk/c0t4d0 0505 stale /dev/dsk/c3t2d0 0505 current
0506 /dev/dsk/c0t4d0 0506 stale /dev/dsk/c3t2d0 0506 current
0507 /dev/dsk/c0t4d0 0507 stale /dev/dsk/c3t2d0 0507 current

That vg04 VG is having only one LV.

Thanks in Advance,
SR

Re: Replacing Failed disk

Bharat Katkar — Thu, 04 Nov 2004 08:16:09 GMT

Hi,

1. Unmount the filesystems from VG04
2. # dd if=/dev/dsk/c0t4d0 of=/dev/null
This will identify the bad blocks in the disk.
3. Use lvsplit to disengage the mirrors and keep you copy on /dev/dsk/c3t2d0 safe.
4. remove /dev/dsk/c0t4d0 and insert new disk.
5. pvcreate
6. Use lvmerge to again mirror your LV

Use lvmerge command carefully. see man lvsplit and lvmerge.

Hope that helps.
Regards,

Re: Replacing Failed disk

Madhu_17 — Thu, 04 Nov 2004 08:35:43 GMT

Thanks for your response.

Can I use lvreduce to unmirror the second copy?

Can i know the exact syntax for these commands?

Re: Replacing Failed disk

D Anderton — Thu, 04 Nov 2004 08:38:47 GMT

First thing confirm the disk has failed and you don't just need to perform an lvsync.

Use ioscan -fnCdisk and check for NO-HW.

Sometime LVM can report the wrong disk has failed when in a mirror, use dd to confirm the failed disk. dd if=/dev/dsk/c0t4d0 of=/dev/null this will hang on a failed disk.

Remove the failed disk from the vg.

lvreduce -m 0 /dev/vg04/lvol1 /dev/dsk/c0t4d0

vgreduce /dev/vg04 /dev/dsk/c0t4d0

replace disk

ioscan -fn

pvcreate /dev/rdsk/c0t4d0

vgextend /dev/vg04 /dev/dsk/c0t4d0

lvextend -m1 /dev/vg04/lvol1

Re: Replacing Failed disk

Madhu_17 — Thu, 04 Nov 2004 08:46:52 GMT

Thanks Damien..

Exactly i need the above commands.

but ioscan of my system is not showing as NO_HW or unidentified sort of error messages.

# ioscan -fnC disk
Class I H/W Path Driver S/W State H/W Type Description
=============================================dev/rdsk/c0t4d0
disk 4 10/0.5.0 sdisk CLAIMED DEVICE SEAGATE ST32171W

can we do anything without replacing this disk.

Can i run lvreduce and vgreduce commands on the mounted filesystem? i believe i can.. correct me, if i'm wrong.

Re: Replacing Failed disk

D Anderton — Thu, 04 Nov 2004 09:14:12 GMT

lvreduce, vgreduce, vgextend etc..etc.. can all be performed online.

Perform the dd to confirm you do have a failed disk, if not it could be that the mirror is just out of sync (stale) :

lvsync /dev/vg04/lvol1

This is not a swap device is it ?

If this is a swap device your lvol will always have stale extents after a reboot if the Mirror Write Consistancy is turned on.

If you confirm you have a failed disk and this is critical data ensure you get a backup.

Re: Replacing Failed disk

Madhu_17 — Thu, 04 Nov 2004 09:25:54 GMT

Yes Damian..

It's not a swap device..

can i run the dd command on a single disk online?

shall i use this command to check the disk status:

dd if=/dev/dsk/c0t4d0 of=/dev/null

Re: Replacing Failed disk

D Anderton — Thu, 04 Nov 2004 09:30:15 GMT

Yes use the dd command online, if the disk is failed your session will probably hang, the command itself will take a while as it is reading the whole disk.