Performance/stability problems on PowerEdge 1950

Harry Roberts harry at telappliant.com
Mon Dec 18 04:49:57 CST 2006


Hi Dean,
  The only thing we've found so far to stop the issue is running RedHat's customized 2.6.9 kernel, I know it won't really help, but if it's an all-or-nothing situation it's either that or re-install with RedHat EL.

OTOH, is anybody here using SAS based 1950s with CentOS under really high disk load?

-----Original Message-----
From: Dean Manners [mailto:deanm at ispone.com.au] 
Sent: 15 December 2006 00:27
To: Harry Roberts; linux-poweredge at dell.com
Subject: RE: Performance/stability problems on PowerEdge 1950

Harry,
	I have an identical anecdote, coming from 1850 to 1950.  Under high disk I/O the machine becomes very laggish and generally performs badly in comparison to the SCSI based 1850's.  Running Debian with 2.6.18, moduled megaraid_sas, sd_mod, scsi_mod. Also keen to hear of any ideas or directions..

Regards
__________________________________________
Dean Manners


> -----Original Message-----
> From: linux-poweredge-bounces at dell.com 
> [mailto:linux-poweredge-bounces at dell.com] On Behalf Of Harry Roberts
> Sent: Thursday, December 14, 2006 11:05 PM
> To: linux-poweredge at dell.com
> Subject: Performance/stability problems on PowerEdge 1950
> 
> 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.
> 
>  Thanks,
> 
> - Harry Roberts
> - Software Developer, Telappliant Ltd.
> - Phone: +44 (0)207 043 3519
> - Email: harry at telappliant.com
> 
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