[DRBD-user] drbd randwrite/write performance is not good

ligong_qiu at sina.com ligong_qiu at sina.com
Thu Nov 24 17:15:58 CET 2016

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


I use a PCI-E flash card and 10Gb ib card to test drbd9. Test tool is fio. I tested 4k randread, 4k read, 512k read, 4k randwrite, 4k write, 512k write, on flash card device, drbd device in standalone status, and drbd device in sync status.

1. read (bandwidth/iops)
/dev/dfa/dev/drbd0/dev/drbd0 standalone 
4k randread630m/158k445m/111k428m/107k 
4k read804m/201k441m/110k423m/105k 
512k read2282m2457m2279m 
2. write/dev/dfa/dev/drbd0/dev/drbd0 standalone 
4k randwrite1424m/364k93m/23k328m/82k 
4k write1455m/372k286m/71k369m/92k 
512k write1785m860m1799m 

Seems write performance droped a lot. Bandwitdh of 4k randwrite is only 93M. I read user guide and tried the recommanded parameter, but it's still no use. Anyone can give some advise?

My fio command:
fio --filename=/dev/drbd0 --direct=1 --rw=randwrite --randrepeat=0 --ioengine=libaio --group_reporting --bs=4k  --iodepth=4 --numjobs=16 --runtime=20 --name=fiotest1 --size=20g

My r0.res config:
[root at app2 drbd.d]# vi r0.res 
resource r0 {
        disk {
                on-io-error     detach;
                disk-flushes no;
                disk-barrier no;
                c-plan-ahead 40;
                c-fill-target 24M;
                c-min-rate 10M;
                c-max-rate 1000M;
                al-extents 6007;

        net {
                protocol A;
                max-buffers     20000;
                max-epoch-size  20000;
                sndbuf-size     0;
                rcvbuf-size     0;
    device /dev/drbd0;
    disk /dev/dfa;
    meta-disk internal;
  on app2 {
  on app3 {


ligong_qiu at sina.com
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