[DRBD-user] drbd performance tuning

Christoph Langbein christoph at greatescape.de
Sat Mar 1 09:42:41 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.

I've setup two debian etch systems with drbd, running vmware images on
this partitions. I'm trying to speedup write performance (and maybe
overall performance;)).
I've setup my network using this values in /etc/sysctl.conf:
# increase TCP max buffer size setable using setsockopt()
net.core.rmem_max = 16777216
net.core.wmem_max = 16777216
# increase Linux autotuning TCP buffer limits
# min, default, and max number of bytes to use
# set max to at least 4MB, or higher if you use very high BDP paths
net.ipv4.tcp_rmem = 4096 87380 16777216
net.ipv4.tcp_wmem = 4096 65536 16777216

# don't cache ssthresh from previous connection
net.ipv4.tcp_no_metrics_save = 1
net.ipv4.tcp_moderate_rcvbuf = 1
# recommended to increase this for 1000 BT or higher
net.core.netdev_max_backlog = 2500
Using Asus P5KC I've GBit Ethernet and issue ifconfig eth1 txqueuelen
1000 when my drbd ethernet device (eth1) comes up.
eth1 is only used to sync drbd.

My drbd.conf is:
global {
    usage-count no;

common {
  syncer { rate 100M; }
resource vmware {
  protocol C;
  handlers {
    pri-on-incon-degr "echo o > /proc/sysrq-trigger ; halt -f";
    pri-lost-after-sb "echo o > /proc/sysrq-trigger ; halt -f";
    local-io-error "echo o > /proc/sysrq-trigger ; halt -f";
    outdate-peer "/usr/sbin/drbd-peer-outdater";

  startup {
    wfc-timeout  0;
    degr-wfc-timeout 120;    # 2 minutes.

  disk {
    on-io-error   detach;

  net {
    max-buffers     8192;

  syncer {
    rate 100M;
    al-extents 257;

  on test1 {
    device     /dev/drbd1;
    disk       /dev/sdb1;
    flexible-meta-disk  internal;

  on test2 {
    device    /dev/drbd1;
    disk      /dev/sda1;
    meta-disk internal;
Can someone explain me how to speedup this setup (Maybe using
JumboFrames on this interfaces) and if it would speedup my system when I
use an external metadisk ? I've seen setups where metadisk is something
like /dev/sda1[1] but I'm not sure what this means.

Thanks in advance

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