I have set up a file server with LVM on top of RAID 5, and seem to be having LVM related performance issue. Interesting details: -Processor: Intel(R) Pentium(R) 4 CPU 2.80GHz with hyperthreading -disks - 4 X Seagate 300 GB - 2 are SATA, connected to MB SATA connectors - 2 are PATA, connected to Promise add in card - OS is centos 4.2 - uname -a -> Linux localhost.localdomain 2.6.9-22.ELsmp #1 SMP Sat Oct 8 19:11:43 CDT 2005 i686 i686 i386 GNU/Linux - all perf numbers obtained using time dd, and were ran 3 times. Run to run variance was within 1 second/run - raid chunk size is 256k, file system block size is 4k, mke2fs was done with stripe=64 I ran three tests, one to the raid device, one to the lvm device, one through the file system. raid device: 118.2 MB/s lvm device: 49.43 MB/s file system: 40.83 MB/s I don't understand the LVM performance effect - I thougt LVM was a pretty straight forward block remapper with negligible performance impact. I'm stunned by the 58% performance penalty. Any thoughts? Any more data that would be helpful? Thanks in advance, Bret --------------------- [root@localhost test]# time dd if=/dev/md1 of=/dev/null bs=1M count=4096 4096+0 records in 4096+0 records out real 0m34.634s user 0m0.021s sys 0m13.467s [root@localhost test]# time dd if=/dev/raid/mirror2 of=/dev/null bs=1M count=4096 4096+0 records in 4096+0 records out real 1m22.863s user 0m0.021s sys 0m14.384s [root@localhost test]# time dd if=testfile of=/dev/null bs=1M count=4096 4096+0 records in 4096+0 records out real 1m40.310s user 0m0.020s sys 0m9.996s _______________________________________________ linux-lvm mailing list linux-lvm@redhat.com https://www.redhat.com/mailman/listinfo/linux-lvm read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
