I am trying to tune my NAS, running openfiler, and wondering why I'm getting relatively poor read performance from 4 WD RE3 drives in RAID 5.
When I run hdparm on the meta device I get the levels of performance I'd expect, drop to the volume and it's a third the speed !
Any one any idea why ? Is LVM that bad ?
[root@nas2 etc]# hdparm -t /dev/md0 /dev/md0: Timing buffered disk reads: 524 MB in 3.01 seconds = 174.04 MB/sec [root@nas2 etc]# hdparm -t /dev/mapper/vg1-vol1 /dev/mapper/vg1-vol1: Timing buffered disk reads: 200 MB in 3.01 seconds = 66.43 MB/sec