[DRBD-user] Write performance problem ?

[drbd at firstcodings.org]

Hi list,

This is a snapshot of my session :
<<
[root at blah1 base]# time dd if=/dev/zero of=bigfile count=100000
100000+0 records in
100000+0 records out

real    0m1.178s
user    0m0.100s
sys     0m1.080s
[root at blah1 base]# ls -al bigfile
-rw-r--r--    1 root     root     51200000 Feb 17 19:37 bigfile
[root at blah1 base]# time sync

real    0m12.875s
user    0m0.000s
sys     0m0.090s
>>

So, knowing that protocol C is in use and from what I understand, it would
mean that it takes about 13 seconds to fully replicate a 50 Mo file to the
secondary....
Network link is Gb, however seems that rate is only about 3.84 MB/s.....
And yes, I've tested the Gb link with dd/netcat : "raw" rate is about 70/80
MB/s.

Here is my config :
<<
  disk {
    on-io-error   detach;
  }
  syncer {
    rate 600M;
    al-extents 257;
  }
  on blah1 {
    device     /dev/drbd0;
    disk       /dev/sda12;
    address    192.168.165.1:7788;
    meta-disk  /dev/sda11[0];
  }
  on blah2 {
    device    /dev/drbd0;
    disk      /dev/rd/c0d1p2;
    address   192.168.165.2:7788;
    meta-disk /dev/rd/c0d1p1[0];
  }
>>

So here is my question : is there a way to boost this 3.84 MB/s rate ?..
Private interfaces have 9000 as MTU.


Thanks to all,

Sylvain H,
DBA.