RAID performance problems

Kevin O Connor kevin at
Sat Jan 25 00:48:41 GMT 2003

just a though but has the card been set to optimize reads. I don't know this 
particular RAID card but most have the ability to use the memory to optimism 
read write or a balance of both

---------- Original Message -----------
From: Dimitris <sehh at>
To: freebsd-users at
Sent: Fri, 24 Jan 2003 18:37:13 +0000
Subject: RAID performance problems

> Hello, i'm using a DELL PowerEdge Expandable RAID controler (PERC 
> 3/DCL, which is the LSI MegaRAID Elite 1600).
> The card is 64bit/66mhz, and its installed in my dual athlon board
> (Asus A7M266-D) on one of the 64bit/66mhz slots. All other slots are 
> empty.
> The problem is that i get very slow writes. Writes are at 20meg/s and
> reads are at 150meg/s. (writes should easily reach 80meg/s)
> The system runs two IBM Ultrastar 73LZX 10k rpm 18gig drives as RAID 
> 0 (64k stripe).
> The problem first appeared under FreeBSD 5.0-R (haven't tried older 
> versions), but i installed WindowsXP just in case the problem was 
> specific to fbsd, but then i got the same performance problem.
> The logical array runs with Direct I/O enabled, WriteThrough enabled,
>  and Adaptive read ahead.
> Anyone seen similar problems? Suggestions are welcome :)
> ------ FreeBSD UK Users' Group  -  Mailing List ------
------- End of Original Message -------

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