[DRBD-user] XenServer 6.0 with DRBD very poor performance

Kuldip Sangha ksangha at tri-tech.com
Fri Apr 6 22:55:16 CEST 2012

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

Hi, I have two XenServers each with Dual Xeon E5320 @ 1.86Ghz, and 24 GB
RAM, 2, 2.0 Terabyte (Green drive) Westernal Digital HD. I am using the
XenServer 6.0 with latest version of DRBD. Both XenServers has
dedicated gigabit NIC (Intel) connected with Cat 6 patch cable (direct
connection), no switch used. i have enable jumbo frames (MTU 9000). Without
DRBD perforamnce are great, but I use DRBD, I am loosing more than 50% of
the performance. 1 MB sequential read is about 118 MB/s without DRBD, with
DRBD it is about 27 MB/s. I get very poor disk read/write. I have enabled
the tweak recommended by Linbit DRBD manual, still nothing seems to work. I
have also, played around with changing syncer rate, nothing helps. I am
using XenServer performance vm for testing the performance. Here is my DRBD
config, how can I speed things up. Please help !!!

# /etc/drbd.d/global_common.conf --------------------------------
global { usage-count yes; }
common {
  protocol C;
  net {
    shared-secret "xenserver";
    after-sb-0pri discard-zero-changes;
    after-sb-1pri consensus;
    after-sb-2pri disconnect;
    max-buffers 8192;
    max-epoch-size 8192;
    sndbuf-size 1024k;
  disk {  max-bio-bvecs 1; }
  handlers { split-brain "/usr/lib/drbd/notify-split-brain.sh"; }
  syncer {rate 40M; al-extents 2099;}

# /etc/drbd.d/drbd-sr1.res --------------------------------------
resource drbd-sr1 {
  device /dev/drbd1;
  disk   /dev/sdc;
  meta-disk internal;
  on Lab-Xen05 { address; }
  on Lab-Xen06 { address; }
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