[DRBD-user] CLVM over DRBD speed test

Federico Simoncelli federico.simoncelli at gmail.com
Fri Jun 26 12:14:26 CEST 2009

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Hi all I was testing the performances of CLVM over DRBD and I found
that the write speed on a logical volume is quite slow (15.1 MB/s)
compared to the write speed on the raw drbd0 device (47.2 MB/s).
Is this a known issue or there might be something wrong in my configuration?

I'm using a Smart Array E200 (128Mb BBWC with cache enabled) which
normally writes at ~50MB/s.
I've a plain drbd.conf configuration (the parameters: al-extents,
sndbuf-size, max-buffers, max-epoch-size, unplug-watermark,
no-disk-barrier, no-disk-flushes, no-md-flushes are set to the default
values).
The connection between the nodes is done with two BCM5722 Gigabit
Ethernet (tg3) with default mtu (1500).

I think my setup shouldn't be the problem since writing on the drbd
device is performing quite well (47.2 MB/s).

Test:

# sync && dd if=/dev/zero of=/dev/drbd0 bs=1M count=100 oflag=direct
100+0 records in
100+0 records out
104857600 bytes (105 MB) copied, 2.22116 seconds, 47.2 MB/s
# pvcreate /dev/drbd0
  Physical volume "/dev/drbd0" successfully created
# vgcreate -cy TestGroup00 /dev/drbd0
  Clustered volume group "TestGroup00" successfully created
# vgs
  VG         #PV #LV #SN Attr   VSize   VFree
  TestGroup00   1   0   0 wz--nc 465.71G 465.71G
  VolGroup00   1   2   0 wz--n- 148.94G      0
# lvcreate -n SpeedTest00 -L 4G TestGroup00
  Logical volume "SpeedTest00" created
# sync && dd if=/dev/zero of=/dev/TestGroup00/SpeedTest00 bs=1M
count=100 oflag=direct
100+0 records in
100+0 records out
104857600 bytes (105 MB) copied, 6.96609 seconds, 15.1 MB/s

-- 
Federico.



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