Date: Mon, 2 May 2005 14:28:42 +0100 From: "Steven Hartland" <killing@multiplay.co.uk> To: "Eric Anderson" <anderson@centtech.com>, "Poul-Henning Kamp" <phk@phk.freebsd.dk> Cc: freebsd-performance@freebsd.org Subject: Re: Very low disk performance on 5.x Message-ID: <002701c54f1a$dde7b0e0$b3db87d4@multiplay.co.uk> References: <17479.1115040178@critter.freebsd.dk>
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----- Original Message -----
From: "Poul-Henning Kamp" <phk@phk.freebsd.dk>
>>Wouldn't this be a problem for writes then too?
>
> I presume you would only compare read to write performance on a RAID5
> device which has battery backed cache.
>
> Without a battery backed cache (or pretending to have one) RAID5
> write performance is abysmall no matter which alignment you use.
This not what's been reported we are seeing writes that are 2x the
speed of reads. Give the additional overhead that writes encure
on RAID5 this should never be the case. The results I go in my tests
where:
RAID5 ( 5 disk )
Read: ~50MB/s
Write: ~140MB/s
Single Disk ( same controller ):
Read: ~50MB/s
Write: ~50MB/s
This just doesn't sit right with me something is seriously wrong.
Steve
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