[DRBD-user] DRBD deadly slow

Felix Zachlod fz.lists at sis-gmbh.info
Thu Nov 13 16:13:42 CET 2008

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.

Hello Group!

I have been trying to set up a drbd configuration with two storage servers
running under rpath Linux (openfiler). The Kernel version is 2.6.26. The
Systems are each running on a q-core Xeon processor, 4GB memory and have a
16 channel icp raid controller with BBWC and are configured with raid 60
underlying. Trying to write to a sample partition /dev/sdbX on each of the
machines will reach about 120MByte/s write performance which seems is poor
for a raid of 16 1TB SATA drives but okay that is not the point here. Trying
to write to the drbd1 device gives a performance of ~ 3MByte/s if both nodes
are online and ~8Mbyte if writing to the primary node where the secondary is
offline. I watched the webinar about performance tuning for drbd and tried
several options such as max-buffers, al-extents and no-disk-flushes which
all in all did not help at all. Performance increases with this tuning
parameters are not more than 10-15 percent whereby this might be measuring
inaccuracy too.

Both machines are connected with two crossover cables and a balance-rr
bonding device which gives a throughput of ~ 210MByte/s using tcp. But the
fact that writing on a local disk is very slow using the drbd driver either
I think the fault has to found somewhere in the io-configuration.

I tested performance using:

dd if=/dev/zero of=/dev/drbd1 bs=512M count=1

giving me a performance of ~ 8Mbyte /s


dd if=/dev/zero of/dev/sdb3 bs=512M count=1

giving me a performance of ~ 110-120Mbyte/s

(where drbd1 is pointing to /dev/sdb1 on each node).

Read performance is not as bad as write performance so I get 230Mbyte/s vs
125Mbyte/s (but its bad enough)

If anyone has a hint what to try next it would be greatly appreciated.

Thank you in advanced 
With kind regards, Felix

More information about the drbd-user mailing list