Performance/stability problems on PowerEdge 1950

Harry Roberts harry at
Thu Dec 14 06:05:02 CST 2006

Hi all,
 We recently upgraded from SCSI based Dell 1850s to SAS based Dell 1950s and found that under the same loads, stresses, applications & conditions the SAS based 1950 system starts failing and becoming unresponsive at a much earlier point.

 One of the main roles of the servers are to perform telephone call recording, which in turn means that there are lots of concurrent writes per second (say 20 per second, per concurrent call). The SCSI based system was able to easily handle 60+ calls, while the SAS based system was having serious problems at around 30.

 We also performed the same tests on a SAS HP DL360 g5 (SmartArray RAID controller), which performed even worse and stopped operating normally at around 7 concurrent calls.

 On both we're using Gentoo with the stock 2.6.18.x kernel and Gentoo's patched 2.6.18.x kernel, we then tested again on a 1950 server using Redhat EL 4, and none of these problems occurred. It seems that something in Redhat's heavily modified 2.6.9 kernel is fixing it - but we can't track down exactly what.

 Has anybody run into similar problems with system load skyrocketing or application response times increasing massively when there's high disk load on SAS any of Dell's SAS based PowerEdge series servers?

 Any ideas or possible directions we could go in are appreciated.


- Harry Roberts
- Software Developer, Telappliant Ltd.
- Phone: +44 (0)207 043 3519
- Email: harry at

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