[DRBD-user] sync rate only 2,204 (1,220) K/sec?

Peter Sabaini peter at sabaini.at
Wed Oct 4 18:36:40 CEST 2006

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


On Wednesday 04 October 2006 16:32, Milind Dumbare wrote:
> On Wed, 2006-10-04 at 16:22 +0200, Peter Sabaini wrote:
> > On Wednesday 04 October 2006 16:19, Milind Dumbare wrote:
> > > On Wed, 2006-10-04 at 16:09 +0200, Peter Sabaini wrote:
> > > > Hello list,
> > > >
> > > > I experimented with drbd a bit; on my first sync it says this in
> > > > /proc/drbd:
> > > >
> > > > # cat /proc/drbd
> > > > version: 0.7.20 (api:79/proto:74)
> > > > SVN Revision: 2260 build by debuild at build64-dapper, 2006-07-20
> > > > 16:42:44 0: cs:SyncSource st:Secondary/Secondary ld:Consistent
> > > >     ns:3214256 nr:0 dw:0 dr:3219148 al:0 bm:196 lo:0 pe:182 ua:1223
> > > > ap:0 [=>..................] sync'ed:  5.7% (52205/55344)M finish:
> > > > 6:11:14 speed: 2,204 (1,220) K/sec
> > > >
> > > > This seems extremely slow -- Hardware is 2xHP DL385 on a Procurve
> > > > Switch with Gigabit connection between them.
> > > >
> > > > The syncer rate in drbd.conf is set to 50M, Protocoll is "C"
> > > >
> > > > dstat gives me:
> > > >
> > > > # dstat 1
> > > > ----total-cpu-usage---- -disk/total -net/total- ---paging--
> > > > ---system-- usr sys idl wai hiq siq|_read write|_recv _send|__in_
> > > > _out_|_int_ _csw_ 0   1   8  90   0   0|   0     0 |   0     0 |   0 
> > > >    0 |1109  1449 0   0   0 100   0   0|   0     0 |2880k  161k|   0  
> > > >   0 |1249  1554 0   1   0  98   0   1|   0     0 |2990k  135k|   0   
> > > >  0 |1144  1410 0   0   0 100   0   0|   0     0 |3004k  152k|   0    
> > > > 0 |1177  1343 0   0   0 100   0   0|   0     0 |2893k  148k|   0    
> > > > 0 |1161  1391 0   0   0 100   0   0|   0     0 |2852k  150k|   0    
> > > > 0 |1197  1451 0   0   0  99   0   0|   0     0 |5915k  306k|   0    
> > > > 0 |2400  2842
> > > >
> > > >
> > > > Usually, I can push 110MB/sec over the wire via NFS.
> > > >
> > > > Am I missing something? Is it only the initial sync thats slow?
> > >
> > > Do you have fast i/o backend? See "$hdparm -t <underlying io device>.
> >
> > # hdparm -t /dev/cciss/c0d0
> >
> > /dev/cciss/c0d0:
> >  Timing buffered disk reads:  208 MB in  3.03 seconds =  68.69 MB/sec
> >
> > It could be better, but its reasonable I think?
>
> Check previous post "Syncer rate limit of 700000K/s" on archive. He had
> same problem.

I did. He misinterpreted the unit of the "rate" setting, right? 

To review:

* I set "rate 50M". I take it this means a rate of 50 Megabyte per second, 
correct?

* /proc/drbd says "speed: 1,512 (1,292) K/sec" which I take it means a little 
more than 1 Megabyte per second, correct?

* So the rate setting does not limit the actual synchronization rate, right?

Still confused .... :-)

Thank you,
peter.


> >  - peter.
> >
> > > > Thanks for any pointers!
> > > > peter.
> > > >
> > > >
> > > >
> > > > _______________________________________________
> > > > drbd-user mailing list
> > > > drbd-user at lists.linbit.com
> > > > http://lists.linbit.com/mailman/listinfo/drbd-user



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