[DRBD-user] Why so slow? Troubleshoot?

Lars Ellenberg lars.ellenberg at linbit.com
Sat Nov 22 23:20:52 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 Sat, Nov 22, 2014 at 07:32:17AM +0100, Christian Völker wrote:
> Hi,
> 
> I have a nearly default setup running. I moved the secondary drbd to a
> VM at it appears to be incredibly slow.
> 
> I need some hints to troubleshoot why it is so slow. See the cat /proc/drbd:
> GIT-hash: a798fa7e274428a357657fb52f0ecf40192c1985 build by
> phil at Build64R6, 2013-09-27 16:00:43
>  0: cs:SyncTarget ro:Secondary/Primary ds:Inconsistent/UpToDate A r-----
>     ns:0 nr:38648 dw:38584 dr:0 al:0 bm:2 lo:16 pe:41 ua:1 ap:0 ep:1
> wo:d oos:1677699908
>         [>....................] sync'ed:  0.1% (1638376/1638412)M
>         finish: 1792:24:51 speed: 244 (256) want: 250 K/sec
> 
> Speed of 244 is ways to slow. It ends up hours later with a io error on
> the disk.
> 
> But when I check performance values I do not see any bottlenecks:
> -CPU IO wait is below 2%
> -CPU itself is ~98%idle
> -network is not busy at all.
> 
> Anyone having a clue why this is so slow?
> Here my drbd.res:
> 
> resource drbd0 {
>   protocol A;
>   startup {
>         wfc-timeout 240;
>         degr-wfc-timeout     120;
>         become-primary-on backuppc;
>         }
>   disk {
>         on-io-error detach;
>         no-disk-flushes;
>         no-md-flushes;
>         use-bmbv;
>         }
>   net {
>         cram-hmac-alg "sha1";
>         shared-secret "ixxxxxxxxxxxxxxi";
>         ping-timeout 100;
>         }
> #  syncer { rate 5M; }

D'oh.

You know, the default happens to be 250k ;-)

lmgtfy: DRBD resync slow

follow the search results to the users guide on www.drbd.org
(keep in mind that some things are different between 8.4 and 8.3)
and follow the search results to the posts on blogs.linbit.com.


>   on backuppc {
>     device /dev/drbd0;
>     disk /dev/vg1/backuppc;
>     address 192.168.34.1:7789;
>     meta-disk internal;
>   }
>   on drbd {
>     device /dev/drbd0;
>     disk /dev/sda;
>     address 192.168.34.16:7789;
>     meta-disk internal;
>   }
> }
> 
> All hints are welcom!
> 
> Thanks
> 
> /Christian

-- 
: Lars Ellenberg
: http://www.LINBIT.com | Your Way to High Availability
: DRBD, Linux-HA  and  Pacemaker support and consulting

DRBD® and LINBIT® are registered trademarks of LINBIT, Austria.
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