amr Serious performance issues

[Hans Rosenfeld <hans%netbsd.org@localhost>]

On Wed, Dec 22, 2010 at 10:26:52PM +0000, Eduardo Horvath wrote:
> On Wed, 22 Dec 2010, Stephan wrote:
> > Does anybody have an idea what causes the poor perfomance on hardware
> > RAID-sets?
> 
> I'd have to know more about the specific controller to be more specific, 
> but mpt is LSI's low end firmware.  It's primarily designed to access 
> drives directly.  They threw in the RAID feature so it looks good on the 
> feature list, but the firmware doesn't really do a good job wih it.  If 
> you want decent H/W RAID performance you should really use LSI's MegaRAID 
> stack.  OTOH if you're not running Windows, software RAID is usually the 
> best idea.

Have you used a MegaRAID recently with 5.1?

I have a similar performance issue with an AMI MegaRAID SCSI 320 without
write cache. On a RAID5 of 4 73GB disks I get about 6MB/s write speed.
Until recently I believed that this just old hardware and lack of write
cache. Then I found out that Linux does about 27MB/s on the same hardware
and configuration.


Hans


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