Comments on: ASM resilvering – or – how to recover your crashed cluster – Test no 3

By: Ronny Egner

Ronny Egner — Wed, 23 Jun 2010 05:15:40 +0000

> the question is does ASM actually search for the member disks in a diskgroup that was created using full disk-device-paths or does ASM just only looks for those devices exactly as they are specified?

ASM is not fixed to device path. If device names change ASM recognizes this and is still able to mount the disk group.

You already tried setting the asm_diskstring parameter. To what value exactly?
Did you check the ASM permissions?
Regarind the example you showed with force-rename. Do NOT do this – it wont change anything.

By: Ayotunde

Ayotunde — Sun, 20 Jun 2010 11:37:04 +0000

I have a configuration where full device-path-names were used to create ASM diskgroups (Oracle DB on Solaris 10).
Recently the LUN IDs were changed on the SAN storage and so the disk-device-names changed (on the Solaris 10 host) and so the ASM could not find/mount the disks for the diskgroups.
I have tried setting the asm_diskstring parameter to a wildcard but that didn’t work (as I suspected). Assuming asm_diskstring is set, the question is does ASM actually search for the member disks in a diskgroup that was created using full disk-device-paths or does ASM just only looks for those devices exactly as they are specified? The rename_dg in 11g has a asm_diskstring parameter that can be set at the diskgroup level and which causes a rediscovery of the disks in a diskgroup, but unfortunately I am on 10gR2. Is there a way to do something similar via ASM or some other Oracle utility? Thanks.

SQL> select adg.name dg_name, ad.name fg_name, path from v$asm_disk ad
right outer join v$ASM_DISKGROUP adg
on ad.group_number=adg.group_number;

DG_NAME FG_NAME PATH
————— ———————- ————————————
DATA1 DATA1_0001 /dev/rdsk/c2t50XXXXXXXXX94FC2d2s0
DATA1 DATA1_0002 /dev/rdsk/c2t50XXXXXXXXX94FC2d3s0
DATA1 DATA1_0000 /dev/rdsk/c2t50XXXXXXXXX94FC2d1s0
DATA1 DATA1_0003 /dev/rdsk/c2t50XXXXXXXXX94DECd11s0
DATA DATA_0000 /dev/rdsk/c2t50XXXXXXXXX94DECd0s0
DATA DATA_0001 /dev/rdsk/c2t50XXXXXXXXX94DECd1s0
FRAD FRADISK5 /dev/rdsk/c2t50XXXXXXXXX94DECd10s0
FRAD FRAD_0005 /dev/rdsk/c2t50XXXXXXXXX94DECd12s0
FRAD FRADISK6 /dev/rdsk/c2t50XXXXXXXXX94FC2d0s0
FRAD FRADISK3 /dev/rdsk/c2t50XXXXXXXXX94DECd9s0
FRAD FRADISK1 /dev/rdsk/c2t50XXXXXXXXX94DECd2s0
FRAD FRSDISK2 /dev/rdsk/c2t50XXXXXXXXX94DECd3s0

12 rows selected.

SQL>

The LUN ID is roughly the 1 or 2 digit number after the small “d” in the device (PATH) names. Some of them changed at the O/S level when LUN ID was changed on the SAN storage.

I was thinking maybe if I run the following sample command (let’s say the device-name for FRDISK6 changed for example):

/etc/init.d/oracleasm force-renamedisk /dev/rdsk/c2t50XXXXXXXXXXXFC2d5s0 FRDISK6

(where /dev/rdsk/c2t50XXXXXXXXXXXFC2d5s0 is the new O/S device for the disk)

Do you think this update ASM as required (including whatever data structures/tables/views) such that the diskgroup(s) will be mountable?

By: gaurav

gaurav — Fri, 09 Apr 2010 06:04:37 +0000

Hi,

Good observation,

I am facing the same problem now i am able to solve with your article.

Keep up the good work.

By: Ronny Egners Blog » ASM resilvering – or – how to recover your crashed cluster

Tue, 27 Oct 2009 07:09:46 +0000

[...] overwriting the ASM disk header with the disk group being offline [...]

By: ronnyegner

ronnyegner — Tue, 20 Oct 2009 13:12:28 +0000

Hi,

yes, you can as long as you give a reference.

By: Polprav

Polprav — Tue, 20 Oct 2009 11:50:17 +0000

Hello from Russia!
Can I quote a post in your blog with the link to you?

By: ASM resilvering – or – how to recover your crashed cluster « Ronny Egner's Blog

Thu, 08 Oct 2009 07:35:33 +0000

[...] overwriting the ASM disk header with the disk group being offline [...]