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

Lars Marowsky-Bree lmb at suse.de
Tue Oct 14 23:17:10 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 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.

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

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).

> 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 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


Teamlead Kernel, SuSE Labs, Research and Development
SUSE LINUX Products GmbH, GF: Markus Rex, HRB 16746 (AG Nürnberg)
"Experience is the name everyone gives to their mistakes." -- Oscar Wilde

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