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Date: Fri, 20 May 2005 07:25:58 +0200
From: Martin Nilsson <martin@gneto.com>
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To: Alexis Yushin <alexis@ww.net>
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cc: freebsd-performance@freebsd.org
Subject: Re: Bad 3ware 9000 performance 5.4?
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Alexis Yushin wrote:
> Hi,
> 
> Running FreeBSD 5.4... three machines with twe/3ware 8000 and three twa/
> 3ware 9500-8 controllers. All of them running RAID 1+0 without write cache
> since we dont have battery backup unit. All of them Seagate 7200 SATA.
> I get about 46Mb/s write on the 8000 series and only 5(!)MB/s on the 9500 series.

I have noticed that the MegaRAID SATA cards sometimes disables the write 
cache on Seagate SATA drives, resulting in a write performance of about 
6MB/s. Can you check if the 3ware also does this. I have had arrays were 
only one disk had write cache disabled and it totally ruined the 
performance of the whole array.

As always be sure to have a good UPS if you are using write cache on the 
disks! With the sad state of todays ATA/SATA disks turning of write 
caching in the drive is often not an option.

/Martin