[nSLUG] raid performance

Rich budman85 at eastlink.ca
Fri Jun 23 00:03:26 ADT 2006


On Thu, 2006-06-22 at 22:54 -0300, Rory wrote:
> I know some folks on this list have experience building heavy lifting
> Linux boxen so here's a quandary:
> 
> Having recently switched to 2.6.15 kernel we are finding that the RAID
> performance completely sucks.  Specifically RAID 10, on Dell 2850 with a
> Perc4 controller.  This is an LSI based controller and therefore uses
> the megaraid driver.  This is initially perplexing given that with the
> new I/O schedulers in 2.6 things should improve.  We've tried all the
> schedulers including the no-op one with no appreciable change in crappy
> performance.
> 

What kernel version is it?  2.6.15-rc5  

I did a quick search on 2.6.15 slow megaraid linux, seems there were
some patches added in rc5.  How you state it works better in 2.4 than
2.6, this could be just that - a driver issue.

Do you use the raid drivers as modules or compiled in?
Many suggest compiling into the kernel because software Raid is very CPU
intensive.  I prefer hardware Raid controllers, just seen too many
software raid mess up when power fails. Hardware at least has the
battery pack to help flush the buffers ensuring all writes are flushed.



Regards
Rich



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