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Re: Scsipi guru needed...
Michael L. Hitch wrote:
> On Sun, 30 Nov 2008, Anders Magnusson wrote:
>> I have been trying to find out why the performance of the ciss
>> controller (Compaq raid) in
>> DL38x is really bad, but as I don't understand anything about the scsipi
>> layer (are there any docs?) I must ask around. All this is really
>> Writing data to the raw sd device (bs=64k) gets just over 7MB/s, which
>> is quite slow.
>> Some debugging showed that:
>> - A write transfer (from given to the ctlr to interrupt) takes 8ms.
>> Ok, no write cache on the ctlr maybe?
> Does your controller have a battery backup? I've found that without the
> battery backup, the controller does not use any write cache and write
> speeds are significantly reduced.
No, it do not AFAIK. But FreeBSD get good speed anyway, and I really doubt
that they fake a write cache.
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