I didn't think lvm2 had such a big performance hit?
65Mb/s on the raid5 device 44Mb/s on the lv
Is this expected?
Kernel 2.6.6
representative dd's:
cu:/huge/editing/tmp# time dd if=/dev/video_vg/video_lv of=/dev/null bs=1024k count=4k
4096+0 records in
4096+0 records out
4294967296 bytes transferred in 97.363340 seconds (44112777 bytes/sec)
real 1m37.437s user 0m0.027s sys 0m27.126s
yet: cu:/huge/editing/tmp# time dd if=/dev/md0 of=/dev/null bs=1024k count=4k 4096+0 records in 4096+0 records out 4294967296 bytes transferred in 65.715222 seconds (65357267 bytes/sec)
real 1m5.770s user 0m0.026s sys 0m27.524s
cu:/huge/editing/tmp# lvdisplay /dev/video_vg/video_lv --- Logical volume --- LV Name /dev/video_vg/video_lv VG Name video_vg LV UUID hyCwfR-d7ZG-lptP-XJFK-vMUb-JWE8-LgQSbb LV Write Access read/write LV Status available # open 2 LV Size 935.00 GB Current LE 14960 Segments 1 Allocation inherit Read ahead sectors 0 Block device 253:0
Changing Read ahead makes no difference (actually it slows it down a touch with values of 10 + 100)
cu:/huge/editing/tmp# vgdisplay /dev/video_vg --- Volume group --- VG Name video_vg System ID Format lvm2 Metadata Areas 1 Metadata Sequence No 6 VG Access read/write VG Status resizable MAX LV 0 Cur LV 1 Open LV 1 Max PV 0 Cur PV 1 Act PV 1 VG Size 935.00 GB PE Size 64.00 MB Total PE 14960 Alloc PE / Size 14960 / 935.00 GB Free PE / Size 0 / 0 VG UUID kFVbcB-UgLa-XQjy-mF7R-BT2D-sUaA-uGUmeK
cu:/huge/editing/tmp# pvdisplay /dev/md0 --- Physical volume --- PV Name /dev/md0 VG Name video_vg PV Size 935.00 GB / not usable 0 Allocatable yes (but full) PE Size (KByte) 65536 Total PE 14960 Free PE 0 Allocated PE 14960 PV UUID pEWAKP-tbaH-DSXP-W2jF-Pg6H-2z35-k1adQj
David
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