Safe to offline a disk in a RAID-5?

[Jonathan Dill]

On May 23, 2008, at 12:35 PM, <Nick_Parrott at dell.com> <Nick_Parrott at dell.com 
 > wrote:
> A drive needs to be "prepared for removal" before swapping it out  
> with a replacement. This is sometimes referred to as "prepare to  
> remove" or "offline" in OMSA. If the disk has failed and rebuilt  
> already, I'd definitely suggest doing one of the above commands  
> before yanking the disk. If the disk is already "failed" or  
> "offline" then it's safer to pull it, but still try the "prepare to  
> remove" if possible.
>
> I've had controllers before now (purely down the nature of SCSI)  
> fail entire arrays when a good *or* bad disk is tugged. It's your  
> call, but we prefer you to prepare the controller for the bad news,  
> just in case.

Yes yes yes!  Also if you have an empty slot in the case, I would  
definitely recommend putting the "new" drive in as a "hot spare" first  
and get the RAID out of degraded mode before you pull out the failed  
drive.  I once pulled a bad drive and had a RAID card go stupid on me  
and forget the whole RAID config, luckily the bad drive was working  
well enough that I could put the bad drive back in, force the RAID to  
ignore its internal config and get the config off the drives.  I hope  
you have good backups and a disaster recovery plan as well.

Jonathan