[DRBD-user] drbd1 write speeds 30% of backing device (CentOS 5.4 drbd 8.3)

Walton Hoops walton at vyper.hopto.org
Thu Dec 10 19:27:22 CET 2009

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



I'm attempting to build a redundant storage solution using drbd replication,

however I can't seem to get the performance I would have expected.


I have the two servers on an Infiniband link, which has tested at about

(Megabytes not Megabits) with netcat (CPU bound).


Both disks write at just under 100MB/s (tested via dd).  Yet when attempting

write to the drbd device on the primary I consistently get 30MB/s.  I assume

the problem must be something I've configured incorrectly, but for the life

me I can't figure out what it is.


My configuration can be found at: http://pastie.org/737624


I have tried Google, and read and played with the tuning recommendations

in the drbd manual, with no success.  In an effort to demonstrate the 

problem is not network speeds, or the secondary,  I have brought down the

secondary, and still see the same performance:


[root at lager ~]# cat /proc/drbd

version: 8.3.2 (api:88/proto:86-90)

GIT-hash: dd7985327f146f33b86d4bff5ca8c94234ce840e build by
mockbuild at v20z-x86-64.home.local, 2009-08-29 14:07:55


 1: cs:WFConnection ro:Primary/Unknown ds:UpToDate/DUnknown C r----

    ns:1048576 nr:0 dw:0 dr:1048576 al:0 bm:64 lo:0 pe:0 ua:0 ap:0 ep:1 wo:b


[root at lager ~]# dd if=/dev/zero of=/dev/drbd1 bs=512M count=2

2+0 records in

2+0 records out

1073741824 bytes (1.1 GB) copied, 32.6865 seconds, 32.8 MB/s


[root at lager ~]# drbdadm down r0


[root at lager ~]# dd if=/dev/zero of=/dev/sda2 bs=512M count=2

2+0 records in

2+0 records out

1073741824 bytes (1.1 GB) copied, 11.1106 seconds, 96.6 MB/s


If anyone has any suggestions as to how I can troubleshoot this further it

would be greatly appreciated.




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