[Ocfs2-users] Slow I/O on ocfs2 file system

[Michal Vyoral]

Hello, 

I have found, that ocfs2 is very slow when doing I/O operation without
cache. See a simple test:

ng-vvv1:~# dd if=/data/verejna/dd-1G bs=1k | dd of=/dev/null
1048576+0 records in
1048576+0 records out
1073741824 bytes (1.1 GB) copied, 395.183 s, 2.7 MB/s
2097152+0 records in
2097152+0 records out
1073741824 bytes (1.1 GB) copied, 395.184 s, 2.7 MB/s

The underlying block device is quite quick:

ng-vvv1:~# dd if=/dev/mapper/3600a0b800067df83000003ba4ba0f5ef bs=1k
count=1M | dd of=/dev/null
1048576+0 records in
1048576+0 records out
2097152+0 records in
2097152+0 records out
1073741824 bytes (1.1 GB) copied, 6.32306 s, 170 MB/s
1073741824 bytes (1.1 GB) copied, 6.32293 s, 170 MB/s

Here is the environment:

* Infrastructure: two nodes, each with two port FC card conected to a
disk array

* OS: Debian GNU/Linux 5.0

* Kernel: 2.6.26-2-amd64

* Ocfs2: 1.4.1

* Multipath:
  # multipath -ll 3600a0b800067df83000003ba4ba0f5ef
  3600a0b800067df83000003ba4ba0f5efdm-7 SUN     ,LCSM100_F     
  [size=100G][features=1 queue_if_no_path][hwhandler=1 rdac]
  \_ round-robin 0 [prio=3][active]
   \_ 7:0:0:0 sdb 8:16  [active][ready]
  \_ round-robin 0 [prio=0][enabled]
   \_ 8:0:0:0 sde 8:64  [active][ghost]


* Creation of the FS:
  # mkfs.ocfs2 -T mail /dev/mapper/mpath0

* Mount parameters:
  # mount | grep verejna
  /dev/mapper/3600a0b800067df83000003ba4ba0f5ef on /data/verejna type
  ocfs2 (rw,_netdev,heartbeat=local)
  # mounted.ocfs2 -d
  Device                FS     UUID
Label
  /dev/sdb              ocfs2  91ae6ead-eee5-42fe-957c-9392e02b5d90  
  /dev/dm-7             ocfs2  91ae6ead-eee5-42fe-957c-9392e02b5d90  

Please, could I ask, what could be wrong? Thanks.

Best regards,
Michal Vyoral