[DRBD-user] Slow Sync Performance

[Roof, Morey R.]

I have been working on a DRBD setup but I am getting really slow sync
performance and after digging around in the lists for a while I still
don't have any idea what is causing the problem so I was hoping someone
can get me some help.

My setup consists of two Dell PowerEdge 2650 servers that are identical.
I have a RAID1 with two 300GB 10K disks that I will be replicating with
DRBD to both machines.  I am using the built in PERC 3/di (aacraid) to
provide the RAID1.  The link is made from the two onboard gige NICs
between the servers and it is using the bonding driver in
active-failover.

I have run iperf on the link between the servers and can get 98 -
75MBytes/sec without problems.

Running a straight dd on the drives I am getting about 34MBytes/sec in
write.

When I setup DRBD the initial syncs runs at an average of 3MBytes/sec.
I have verifed that DRBD is using the correct interfaces between the
machines and have tried changing the al-extents, sndbuf-size,
max-buffers, max-epoch-size, unplug-watermark and such as others have
mentioned on the list but it always runs at about 3MBytes/sec.

The OS is CentOS 5.1 and I am starting to wonder if there might be
something odd in it.  Below is a copy of a my simple DRBD config that I
have been messing around with trying to get this all work.

Any help would be wonderful.

Thanks,

Morey


global {
        usage-count no;
}

common {
        protocol C;

        syncer {
                rate 40M;
        }

        net {
                sndbuf-size             512k;
        }
}

resource r0 {
  on nas1.nmt.edu {
    device     /dev/drbd0;
    disk       /dev/sdb1;
    address    10.180.0.10:7789;
    meta-disk  internal;
  }

  on nas2.nmt.edu {
    device    /dev/drbd0;
    disk      /dev/sdb1;
    address   10.180.0.20:7789;
    meta-disk internal;
  }
}