[DRBD-user] Write performance problem ?

drbd at firstcodings.org drbd at firstcodings.org
Mon Feb 21 12:09:24 CET 2005

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

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
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

Here is my config :
  disk {
    on-io-error   detach;
  syncer {
    rate 600M;
    al-extents 257;
  on blah1 {
    device     /dev/drbd0;
    disk       /dev/sda12;
    meta-disk  /dev/sda11[0];
  on blah2 {
    device    /dev/drbd0;
    disk      /dev/rd/c0d1p2;
    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,

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