questions about a PERC in a 2950

Brice Figureau brice+dell at daysofwonder.com
Wed Oct 17 03:24:15 CDT 2007


On Tue, 2007-10-16 at 09:39 -0700, Chris Stromsoe wrote:
> On Tue, 16 Oct 2007, McDougall, Marshall (FSH) wrote:
> 
> >> I have a couple of 2950s that have PERC controllers.  I'd like to 
> >> disable the PERC controller and drop back to using the SAS 5i 
> >> controller.  Is that possible / something that I can do in the field by 
> >> fiddling with switches, or does it require parts replacement?  If it's 
> >> not possible, is it possible to use the PERC as a straight SCSI 
> >> controller, without having to make each drive into single disk raid0?
> >
> > Chris.
> >
> > I don't have an answer to your question, but I am curious as to why you 
> > want to dump the PERC?
> 
> I'm not a fan of hardware raid.  Getting the data off the drives if 
> something goes very bad can be challenging.  With 8 cores in the box in 
> question, I'm not lacking for CPU.  The management tools leave quite a bit 
> to be desired, not the least of which is that there isn't a simple proc or 
> sysfs interface for managing the driver (using sh and echo to manage drive 
> replacement, rebuilds, hot spares, etc, with cat for reading back 
> controller and drive status would be perfect).  I'm also running Debian 
> and there isn't a Debian native build of the management tools or available 
> source to build them myself.

The big advantage of hardware RAID is the hardware battery-backed RAM
cache that is on the card.

I find this piece of hardware essential for both performance (it absorbs
disk flush gracefully) and reliability (your filesystems have better
chance to survive in case of power problems)...

But you are right, management tools are way too complex, too closed, and
don't obey standard unix paradigms... 
Hopefully there is an open-source alternative (I don't know if it
supports PERC5, it is working fine for my PERC4 cards):
http://sourceforge.net/projects/megactl
-- 
Brice Figureau <brice+dell at daysofwonder.com>



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