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Re: OT: FC4+Poweredge 850+Perc 4/sc = slow disk performance



On Fri, 2006-28-04 at 12:58 -0700, Mike McMullen wrote:
> Can anyone shed any light on why the i/o appears so slow? On 7500 RPM
> SATA with drives I get buffered reads of around ~60-70MB.

I have no idea - not a hardware guy.  However, just for your
information, this is what I get on a Dell PE 1600SC with a PERC 4/SC,
and two SCSI 10K RPM drives in RAID 1, running RHEL 4:

/dev/sda:
 Timing cached reads:   1748 MB in  2.00 seconds = 874.13 MB/sec
 Timing buffered disk reads:  202 MB in  3.03 seconds =  66.68 MB/sec

I did that a few times, and the times were fairly consistent.  However,
I couldn't take the server offline, so it was done while it was in
runlevel 3.

As you can see, my buffered reads are about what you're expecting.  My
cached reads are much slower, though.  Not sure why...

Oh, you should check out the Dell Linux mailing list.  You'll more than
likely get more informed answers there.

HTH,

Ranbir
-- 
Kanwar Ranbir Sandhu
Linux 2.6.16-1.2069_FC4 i686 GNU/Linux 
21:43:58 up 23 min, 2 users, load average: 0.27, 0.28, 0.31 



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