[DRBD-user] Performance problem in one direction

[Frank Müller]

Hi everybody,

I've got two hosts, hostA and hostB, which are connected by crossover
cable and 1gbit full duplex interfaces.
My problem is, that syncing from hostA to hostB is much slower than the
other way round.

Synchronization from hostA to hostB runs with just 5-6Mb/s.
>From hostB to hostA it runs with about 30-35Mb/s.

When I copy something directly over the net, or use netcat, the rate in
both directions is about 30-35Mb.
That's not fast for a gigabit connection though, but at least it's
something.

hostA boots from a fibrechannel raid and has got 36gb of ram.
It's a Supermicro Server with Intel 82576 nics.

hostB uses local storage as raid5 and 16gb ram.
It's a HP DL360 G6 with Broadcom BCM5709 nics.

My drbd.conf looks like this:
resource data {
         protocol C;

        handlers {
         outdate-peer "/usr/lib/heartbeat/drbd-peer-outdater -t 5";
          }
        net {
        }
        startup {
          degr-wfc-timeout 80;
        }
        disk {
          on-io-error        detach;
        }
        syncer {
           rate     60M;
        }

        on hostA {
            device /dev/drbd0;
            disk   /dev/mapper/disk1-part2;
            address     172.127.0.1:7789;
            meta-disk internal;
           }
        on hostB {
            device /dev/drbd0;
            disk   /dev/cciss/c0d1p1;
            address     172.127.0.2:7789;
            meta-disk internal;
        }
}

I tried different tunig parameters like no-disk-flushes, no-md-flushes,
no-disk-barrier and different values for al-extents, but none of them
had a signinficant effect on the sync rate.

Any tips? I'm clueless.

Thanks in advance,

Frank