[DRBD-user] resync-rate not applied

Nik Martin nik.martin at nfinausa.com
Tue Aug 14 15:51:38 CEST 2012

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

On 08/13/2012 07:43 PM, Dennis Jacobfeuerborn wrote:
> On 08/03/2012 03:27 AM, Dennis Jacobfeuerborn wrote:
>> Hi,
>> I just set up a traditional drbd primary/secondary system between two hosts
>> that are connected with gigabit ports. The problem is that the resync rate
>> is only 5M even though in the config file I set it to 40M.
>> I also tried:
>> drbdadm disk-options --resync-rate=40M drbd1
>> which doesn't result in an error but apparently doesn't get applied either.
>> I also tried 1M but that gets ignored too.
>> Any idea what might be going on here?
>> (This is drbd 8.4.1 on a Centos 6.3 system)
There is also a setting called
  c-max-rate that if not set, is set to 20M I think.

Also, the wild jumping around sounds like a network issue.  I have a 
10GB crossover cable connecting my two DRBD nodes, and have jumbo frames 
turned on, and can get near wire speed (of the disk bus) through it. 
Are you doing sync through a switch?  If so, are your MTUs set 
consistently?  Do you have any type of broadcast storm control in your 
switches?  I think DRBD will trigger storm control in switches too.

> Does nobody have any idea?
> I just had to re-sync and the "want" value jumped around wildly between 0
> K/sec and 80.000 K/sec and the speed it self is terrible:
> 	finish: 0:05:07 speed: 608 (628) want: 7,160 K/sec
> 	finish: 0:04:33 speed: 684 (628) want: 43,760 K/sec
> 	finish: 0:04:38 speed: 680 (628) want: 9,600 K/sec
> 	finish: 0:05:04 speed: 624 (628) want: 0 K/sec
> 	finish: 0:04:51 speed: 648 (628) want: 10,760 K/sec
> It looks like the variable sync mechanism does more harm than good and I
> don't seem to be able to turn it off properly.
> Regards,
>    Dennis
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