raid 5 with ASM

[satish]

Dear Erman,

We are storing datafiles in external Diskgroup and we are relying on storage for mirroring using raid 5 disks.i have concern here and need your suggestions

will storage takes care of metadata mirroring as well?
if metadata of some disk is corrupted,will the diskgroup still remain mounted?

Thanks for all the support

[ErmanArslansOracleBlog]

The raid mechanism in storage will protect anything (metadata, data anything) that you wrote on the relevant disks.
However; you need to understand one thing.
You give luns from storage.
That luns are coming from a raid group. (group of disks)
So, as long as you have raid there, it will protected.
But, if you corrupt the metadata  of a disk from OS by writing it, then the protection can 't do anything about it.

[satish]

In this case,if metadata of one disk is corrupted in raid 5 disks, asm should not be impacted as we will have mirror right?

Pls correct me if i m wrong

[ErmanArslansOracleBlog]

You are mixing the terms and you are mixing the layers.
What do you mean by header corruption?
Are you talking about a logical corruption?

Raid protects you physically. But if you have a corrupted header (the things written in the header is corrupt/wrong), then raid can't do anything.

[satish]

Thanks for the update erman.if logical corruption like metadata corruption in external redundancy disk group,then raid can't help and diskgroup will be dismounted.pls correct me if my final understanding is wrong

[ErmanArslansOracleBlog]

If there is a logical corruption. I mean if the things written in the header are physically okay but logically not okay, then you should correct them using a tool.. ASM or raid can't do nothing here.

I think you need to read more on Raid.
It is for fixing the physical things. Raid doesn't know Oracle, or Oracle Format.. So it is normal that Raid can't help you here.