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Re: raid 10 su, sw settings

To: Justin Piszcz <jpiszcz@xxxxxxxxxxxxxxx>
Subject: Re: raid 10 su, sw settings
From: Iustin Pop <iusty@xxxxxxxxx>
Date: Mon, 31 Dec 2007 21:17:12 +0100
Cc: Brad Langhorst <brad@xxxxxxxxxxxxx>, xfs@xxxxxxxxxxx
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On Mon, Dec 31, 2007 at 02:07:27PM -0500, Justin Piszcz wrote:
>
>
> On Mon, 31 Dec 2007, Brad Langhorst wrote:
>
>>
>> On Mon, 2007-12-31 at 12:04 -0500, Justin Piszcz wrote:
>>
>>>>
>>>> Typical blocks/sec from iostat during large file movements is about
>>>> 100M/s read and 80M/s write.
>>>>
>>>
>>> #1 What type of performance do you expect with a 4-disk raid10?
>>
>> Are you saying that i should not expect more?
>> I expect about 70% better performance, since I think a single disk
>> should be able to do 100M/s. Maybe this is unreasonable?
> A single disk may do 90MiB/s burst but not sustained for read or write, at 
> least not cheap SATA disks and when you get toward the middle part of the 
> disk the speed wil drop off significantly.  100MiB/s read and 80MiB/s write 
> for RAID10 sounds about right to me.  Maybe someone else on the list with a 
> similar configuration can chime in with their benchmarks.

I agree about the disk speed - 100MiB/s for SATA drives is a little bit
too much to expect. And certainly, *only* in purely single-reader or
single-writer sequential workloads.

I have the same config - 4 drive hw raid10 on 9650. A recent zcav log
shows read speeds start at around 140MiB/s and decrease toward 75MiB/s.
Since this is zcav from the bonie++ package, it doesn't take into
account any filesystem or partitioning overhead.

regards,
iustin


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