PE2950 III & Xen crashiness

Bill McGonigle bill at bfccomputing.com
Thu Sep 11 12:23:49 CDT 2008


Hi,

I'm wondering if anybody is having either good or bad luck with  
PowerEdge 2950 Mark III machines and Xen.

We've got a pair of them with 12GB of RAM and 8x146GB 2.5" SAS drives  
and are running current 32-bit CentOS 5.2.  There are at least three  
problems:

1) kernel panics in megaraid_sas, generally related to high disk  
activity (e.g. 2 scp's of large files to dom0).  The controller is a  
"MegaRAID SAS 1078 (rev 04)".

2) slow real-world performance.  For instance, re-compiling a kernel  
on these (2.66GHz 2x4 Xeon CPU's) takes about twice as long as on a  
SuperMicro server with 2.0GHzx2x4 Xeon's and 3.5" 7200RPM drives on a  
3Ware controller (both machines just booted into dom0).  The 2.5"  
drives actually bench faster with hdparm and dd, but doing a  
filesystem copy between RAID devices is about 50% slower.  Linux RAID  
1 on both.

3) crashes on Xen domU creation after a period of high disk activity  
(e.g. cloning a vm's disk image and creating its DomU).  Once this  
caused an automatic reboot, though I'm not sure how that happened.

These problems are on both machines, so I'm assuming it's not just a  
single bad server or component.  The CentOS megasas driver was one  
version behind current so we updated to current with dkms, but that  
didn't make a material difference.  Otherwise BIOS and firmwares are  
up-to-date.

I haven't experienced Xen crashiness before (in recent history  
anyway), but this is the first time I've tried it on Dell servers, so  
I'm wondering if anybody else is using it (or decided not to) on this  
kind of hardware.

Thanks,
-Bill

-----
Bill McGonigle, Owner           Work: 603.448.4440
BFC Computing, LLC              Home: 603.448.1668
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