What model server is this? What level raid is the software raid volume, how many drives and what type?
How did you exactly establish the performance number? I have done performance benchmarking with LVM over hardware raid luns had have not been able to show a significant performance degradation, and it is actually faster when you stripe across several raid-protected luns. Some general disk benchmarking rules: Write at least twice as large files as you have RAM (so that's 8G minimum in your case) so caching does not inflate the numbers. Also don't forget to measure the time for it to be synced to disk. Example for large block I/O large file benchmarking on a 4G system: time dd if=/dev/zero of=/mnt/targetfilesystem/largefile bs=1M count=8192 time sync If you divide 8192 by the aggragate of the seconds used by both commands then you have a good MB/s estimate. For read you can just do: time dd of=/dev/null if=/mnt/targetfilesystem/largefile bs=1M count=8192 To do some more intense testing including mixed read/write, I use bonnie++. If you want to turn it into a real science and get very specific data for specific access patterns, you might want to look at iozone. Michael -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Judd Tracy Sent: Friday, May 04, 2007 6:41 AM To: [email protected] Subject: [Beowulf] LVM performance problems I am trying to bring up a small file server and am noticing some serious performance issues when using LVM. I created a software raid /dev/md0 which I can read at ~195MB/s using the raw raid device, but as soon as I put LVM on top of it the read speeds drop to ~95MB/s using a raw lvm partition without a filesystem. When I use and xfs filesystem on top of the lvm partition it drops down to ~40MB/s. This seems like a processing power issue, but the machine is a dual processor opteron system with 4GB of ram in it. Does anyone have some insight into why I might be having such problems with the system. Judd Tracy Institute for Simulation and Training University of Central Florida _______________________________________________ Beowulf mailing list, [email protected] To change your subscription (digest mode or unsubscribe) visit http://www.beowulf.org/mailman/listinfo/beowulf _______________________________________________ Beowulf mailing list, [email protected] To change your subscription (digest mode or unsubscribe) visit http://www.beowulf.org/mailman/listinfo/beowulf
