Wednesday, July 20, 2011

Kfed saved the Day =ASM Disk Header recovery

I just wanted to start this Blogpost as a quick note to myself to investigate and learn about kfed.
I was hit with a situation this morning where during a system migration the ASM headers were overwritten/blanked out in AIX. this was done with a process that is used to provision new ASM Luns in our environment
In AIX you can use
lquerypv -h to see the header of the disk which tells you that it is an ASM disk and what Diskgroup is attached to . if the pvid is cleared from such a disk after the header is written it will clear the header thus allowing for reuse of the disk.
we were stuck with such a situation with my database backup on the same disk and no metadata backup at all. ( Shame on me for not setting up these vital components early enough). This caused panic and chaos . A colleague googled thru and found references to kfed Here , Here and Here.

We looked at all the disk headers using lquerypv and then were able to use kfed  repair on each disk to get the headers back.
There aredetails  about  kfed in the links above and it is still and undocumented oracle utility so use with care. All i can say is kfed saved the day for us in a situation where we were in no hope of recovery.
A nice tool to have and learn about

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