Re: Naive view of Oracle on RAID Subsystem?

>Could you give some examples (or at least one good one) of where RAID won't
>save you?

First off, let me make it clear that I'm not saying RAID is a bad thing. Actually I think a good raid subsystem is better than sliced bread and everybody should have one. But it is not the final word in your backup plan and the presence of a RAID drive shouldn't be an excuse to do something stupid.

My systems group just installed a RAID device and argued that we didn't need to worry about the offline redologs and database being on the same device because the odds against two disk going out at the same time were 'astronomical'. So a single failure would never hose the database and our archive logs.

Fine. Except that when they forgot to put the terminator block back on the subsystem cabinet after an equipment move writes to all filesystems on the RAID device were corrupted.

We had to bring 3 databases back from backup and couldn't roll them forward because some of the archive logs where bad.

Let's not forget that in many raid devices you still only have one controller, one SCSI cable and one powersupply unless you go out of your way to add them. RAID is not fault tolerant by definition. Just fault forgiving.

Finally how is RAID going to help you if a user deleted the wrong table or the SYSADM removed a datafile? It ain't.

>I need something concrete about pitfalls and disadvantages

The only pitfalls are if you bring in RAID expecting it to be the magic bullet that fixes all the problems you every had. Dont use the above examples as an excuse not to implement RAID, use them as an excuse to implement a backup/recovery plan correctly.

-- 
Regards, 

Lee E. Parsons                  		
Systems Oracle DBA	 			lparsons_at_world.std.com