[Gllug] Hardware SCSI RAID

[Mike Brodbelt]

On Wed, 2006-01-18 at 14:04 +0000, Matthew Cooke wrote:
> gah. had software raid on fedora and wasn't impressed at all. a disk failed 
> and wrote something into a log and I didn't notice for 2 months. Also, 
> replacing a failed disk seemed non-trivial.
> 
> I was under the impression that the adaptec scsi/raid were pretty popular 
> but you have made me nervous now!

I've used hardware SCSI RAID on servers for years, and it's saved me a
lot of hassle.... I would always go for h/w RAID on servers where
possible, preferably with hot swap disks.

Yes, the on disk format may well be controller specific, but if you're
running a server the RAID is your first level of protection, and you
should have a decent backup plan, so you're ability to read the bare
disks really shouldn't matter. If it does, there's something seriously
wrong with your backup strategy.

You want to make sure that the RAID card you have is real h/w RAID. It
should have a dedicated RAID processor, and its own SCSI BIOS with
management features. To set it up, you will not usually need to format
the disks using the RAID card, but you will normally have to go through
some process to initialise the array. The array build may well take most
of a day to complete. Once this is done, the RAID card should present
the array to the host computer as a single disk.

RAID cards can be very picky about cabling and termination - it has to
be decent quality. Make sure your disks are operating at the same speed
- if the card drops the speed back this might indicate a cabling
problem.

I've used ICP Vortex cards on machines - they're very nice. If a disk
fails there's an audible alarm you can't easily miss, and the card can
be controlled from its own BIOS (so you can setup arrays with no OS
installed), or from a curses based utility that gives full access to the
feature set. I'd recommend them without hesitation.

Mike

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