Re: Soft-/Hardware RAID Performance

[Gregory Leblanc <gleblanc@linuxweasel.com>]

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On Thu, 2003-02-20 at 02:55, Daniel Brockhaus wrote:
[snip]
> One suggestion to speed up the reads was to issue several reads in 
> parallel. Silly me didn't think of that, I was completely focused on the 
> writes, which are more important for my application. Anyway. Using parallel 
> reads (from four processes), read performance scales almost with the number 
> of disks in the array. This goes for both, hardware and software RAID, with 
> software RAID being about 15% faster.
> 
> Write performance on the other hand does not change at all when using 
> multiple processes - for obvious reasons: The kernel queues, sorts and 
> merges write requests anyway, so the number of processes doing the writes 
> does not matter. But I've noticed something peculiar: If I change my 
> benchmark to write 4K blocks at 4K boundaries, write performance increases 
> to almost 300%. This is quite logical, since the kernel can write a 'page 

What was your previous benchmark write size?  And what parameters did
you use when creating the RAID 0 array and filesystem?  There may be
opportunities for tuning there.
	Greg
[snip]

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