Subject: Re: RAID In general (Re: Hot Swappable IDE Kits)
To: Chuck Yerkes <>
From: Greg Oster <>
List: current-users
Date: 04/16/2003 13:55:52
Chuck Yerkes writes:
> Quoting Caffeinate The World (
> > For SCSI we have scsictl to rescan the bus. What about IDE? I see these
> > hotswappable IDE kits. How do they work? Does NetBSD support it?
> Look, you seem to be obsessing on the importance of RAID
> and removable disks.  I've used this forever for ANY OS.
> My MAC can deal with it.
> I use something called: HARDWARE RAID.
> My machine sees a SCSI drive with 500GB (or 5GB when I started with
> HW Raid units).
> Disk dies and I get notified over serial, an audible alarm
> goes off, wahtever.  A spare is brought in if appropriate
> (not for stripes, but yes for RAID 3/5).  I can pull the bad
> disk or power supply or cable and put a new one in.
> If it saves me 5 days of fighting software raid per year,
> it costs $0 over 3 years.
> Yes, software raid is cheaper to acquire.  But it's slower

Do you have pointers to any specifics on this?  I'd be quite interested in 
seeing benchmarks for "modern" hardware... (preferably using the same disks 
on the same hardware)

> and costs far more in maintainance.
> Oh, lose the boot disk or CPU and you can't just run the disk case
> to another machine and have the data available - in seconds - unless
> you are the unusual one to make sure that you have the configs
> located elsewhere for immediate use in a panic.

Um... RAIDframe's component labels let you do just that.  You might have to 
adjust an fstab or something, but you'd need to do that in the hardware RAID 
case as well.  (I won't ask what happens if you happen to get disks put into
the wrong slots in a hardware RAID ;)  I know what happens when you do that
with RAIDframe, and it's not a problem :) ).

(Our server rack has a bunch of IBM x330's w/ dual U160 SCSI in hot-swap 
trays (NetBSD/i386, RAIDframe RAID 1).  If something (other than disk) in 
one of our servers dies, we simply move the disks from one unit to another, 
boot the machine, and away we go.  And it doesn't even matter if we forget 
which disk was in what slot :) ).
> Bring a RAID set down for 4 hours in a busy office and you've
> cost yourself FAR FAR more than HW raid costs.

Or, have a proprietary controller die on you (having no spare available), 
and you're in the same boat.

Hardware RAID does have it's advantages, but there's usually still some 
"software RAID" running on that RAID card :)


Greg Oster