Hard Disk IDs in Linux

Daniel Fussell dfussell at byu.edu
Thu Mar 14 16:25:03 MDT 2013

On 03/14/2013 08:47 AM, Nicholas Leippe wrote:
> But still, now you have introduced a CPU-bound
> task for each write I/O operation which is why in some cases dedicated
> hw raid which offloads the parity calculation can help. (however IME
> hw raid has been slower than the linux md driver)
Did you have the disk caches turned off?  I read a few months ago that 
the md driver does outperform hardware raid, but only with the caches 
turned on.  When they were turned off, it's speed dropped to be the same 
as hardware raid, if not slightly worse.

;-Daniel Fussell

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