[DRBD-user] 40MBps Sync Limit 8.4.4 and Above

Matt Kereczman matt at linbit.com
Wed Nov 19 22:29:14 CET 2014

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

On 11/18/2014 09:44 AM, Darren Ginter wrote:
> Hello all,
> With Ubuntu 14.04 (drbd 8.4.4), I cannot get more than 40MBps out of the
> initial DRBD initialization sync no matter what settings (sync-rate,
> c-max-rate, c-min-rate, etc).  I've been playing with this for tens of
> hours now.  I've tried drbd 8.4.5 and above to no avail.
> With Ubuntu 12.04 (drbd 8.4.3) I can max out a 10GbE NIC without issue on
> the same hardware.

You may need to tune 'max-buffers' and 'max-epoch-size' to get some more
performance out of the secondary node. This is outlined in the user's
guide (section 15.3.1).

I have the values below configured on a system running DRBD 8.4.5,
resyncing at ~400MiB/s (almost the max write speed of the backing disk):

resource <resource> {
  net {
    max-buffers 80k;
    max-epoch-size 20k;

Those settings are a little extreme; start at 8000, and tune accordingly.

: Matt Kereczman
: LINBIT | "Your Way to High Availability"
: 1-503-573-1262 x200 | 1-877-4-LINBIT
: Web: http://www.linbit.com

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