[DRBD-user] Slow write performance with 10 Gig Ethernet

Felix Arbach felixarbach at yahoo.com
Wed Nov 18 20:09:02 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 have two identical servers equipped with 10 GigE cards. MTU is set to 9000 and with iperf i got over 9 Gbit/s over my network connection. The servers are directly connected. The disks (10x 2 TB SATA, RAID 6) are quite fast. I got about 700 MB/s write speed with drbd standalone. With drbd connected the write speed drops to about 150 MB/s. The sync-rate is at about 290 MB/s. Why is my write speed so slow?

Here is my drbd.conf:

global {
  usage-count no;

common {
  protocol A;
  syncer { rate 900M; al-extents 3833; }
  net { max-buffers 8192; }

resource r0 {
  on brick1.myserver.com {
    device    /dev/drbd0;
    disk      /dev/sdb1;
    flexible-meta-disk /dev/sdc1;
  on brick2.myserver.com {
    device    /dev/drbd0;
    disk      /dev/sdc1;
    flexible-meta-disk /dev/sdb1;

Any ideas? Thanks for your help!

Best regards,

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