Re: Very slow LVM performance

[Arcady Genkin <agenkin@gmail.com>]

I just tried to use LVM for striping the RAID1 triplets together
(instead of MD).  Using the following three commands to create the
logical volume, I get 550 MB/s sequential read speed, which is quite
faster than before, but is still 10% slower than what plain MD RAID0
stripe can do with the same disks (612 MB/s).

  pvcreate /dev/md{0,5,1,6,2,7,3,8,4,9}
  vgcreate vg0 /dev/md{0,5,1,6,2,7,3,8,4,9}
  lvcreate -i 10 -I 1024 -l 102390 vg0

test4:~# dd of=/dev/null bs=8K count=2500000 if=/dev/vg0/lvol0
2500000+0 records in
2500000+0 records out
20480000000 bytes (20 GB) copied, 37.2381 s, 550 MB/s

I would still like to know why LVM on top of RAID0 performs so poorly
in our case.
-- 
Arcady Genkin