Re: RAID-5 streaming read performance

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On Thu, 2005-07-14 at 08:38 +1000, Neil Brown wrote:
> On Wednesday July 13, jdc@xxxxxx wrote:
> > Here's a question for people running software raid-5:  do you get
> > significantly better read speed from a raid-5 device than from it's
> > component partitions/hard drives, using the simple dd test I did?
> 
> SCSI-160 bus, using just 4 of the 15000rpm drives:
> 
> each drive by itself delivers about 67M/s
> Three drives in parallel deliver 40M/s each, total of 120M/s
> 4 give 30M/s each or a total of 120M/s
> 
> raid5 over 4 drives delivers 132M/s
why here a 132MB/s instead of 120MB/s (3 * 40MB/s) as u mentioned? any
factor lead to this increase?


> 
> (We've just ordered a SCSI-320 card to make better use of the drives).
> 
> So with top-quality (and price) hardware, it seems to do the right
> thing.
> 
> NeilBrown
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