[DRBD-user] drbd is performing at 12 MB/sec on recent hardware

Bart Coninckx bart.coninckx at telenet.be
Wed Oct 15 10:17:24 CEST 2008

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

On Tuesday 14 October 2008 23:17, Lars Marowsky-Bree wrote:
> On 2008-10-14T18:32:50, Bart Coninckx <bart.coninckx at telenet.be> wrote:
> > Hi all,
> >
> > I previously posted about a sync going somewhat slow (managed to get it
> > up to 18MB/sec).
> > I figured this could be just the syncing, so I decided to do some
> > performance tests as mentionned in the webinar.
> >
> > I used:
> > dd if=/dev/zero of=/dev/drbd0 bs=1G count=1 oflag=direct
> oflag=direct uses direct sync'ing (obviously), which means there's not
> very much optimization going on. bs=1G also means that a huge memory
> block is allocated and flushed.

I see. I used this exact command from the webinar, assuming it was a good way 
to test performance.

> So at least these parameters are far from sane - bs=16384 oflag=fsync
> might provide better performance.

I get about 1.3 MB/sec when using these values  :-s

> The next step might be to check whether you're using internal meta-data,
> which also might not exactly perform very well (seek time issues).

I indeed use internal meta-data. There is somewhat of a problem in using 
external meta-data since I have no disk left. I could reconfigure the RAID-5 
and dedicate a virtual disk to this, but would this enhance performance?

> > The server is a HP ML370 G5 with a 1TB RAID-5 setup. The controller used
> > the cciss driver. DRBD is 0.7.22. OS is SLES 10 SP1. The network link is
> > gigabit, full duplex, set to 1000 Mbit.
> Of course, I am inclined to advise an upgrade to SP2, which might help
> with a newer cciss driver ;-)

I also use OES2, which doesn't work with SP2 I'm told. But I could always 
extract the driver ...

> > I plan to enable write back cache, but I wonder if that is going to make
> > THE difference.
> If you're using internal metadata, that is going to make a huge
> difference.

OK, will try that then! Thank you!!!


> Regards,
>     Lars

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