Dell Poweredge 2950 with PERC 5/i RAID

Andrew Moise chops at demiurgestudios.com
Mon Oct 9 14:57:15 CDT 2006


On 10/9/06, Claudio Nasuti <claudio.nasuti at acsys.it> wrote:
> I just installed RHEL 4 U4 on a PowerEdge 2950
> configured as follow:
> a xeon 5150
> two gigabytes of ram
> six internal disks, 300 gigabyte SAS 10.000 rpm, factory configured in a single raid 5 container
>
> The installation went smooth like a breeze but when I made a small IO test I have been shocked
> IO seems very poor as everyone can figure by numbers
> [root at adm-sdf1 ~]# time dd if=/dev/zero of=./DummyFile bs=65536 count=65536
> 65536+0 records in
> 65536+0 records out
>
> real    1m49.236s
> user    0m0.032s
> sys     0m8.348s

  I have a PE 2950 with RAID 5 (4x500GB SATA), and I get quite good
disk performance:

moise at breakout:~$ sudo sync && sudo time dd if=/dev/zero
of=/opt/perforce/depot/test bs=65536 count=65536 && sudo time sync
65536+0 records in
65536+0 records out
4294967296 bytes transferred in 19.457283 seconds (220738288 bytes/sec)
0.02user 7.27system 0:19.45elapsed 37%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (0major+196minor)pagefaults 0swaps
0.00user 0.50system 0:17.60elapsed 2%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (0major+160minor)pagefaults 0swaps

  ... so it's a total of 37.05 seconds to write 4 gigabytes, or 110
MiB/sec, which is consistent with the performance I see in general.
When I first installed this system, though, I had some trouble with
the RAID controller resetting frequently, with associated 30-second
delays.  If you're experiencing similar delays, that might explain the
slow performance.  You can see my post at
http://lists.us.dell.com/pipermail/linux-poweredge/2006-October/027535.html
; do you see messages in dmesg that are similar to the ones in that
post?



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