[DRBD-user] degraded write performace

[Jeff Buck]

OK, I haven't been paying attention which means this is probably a
stupid question, but is there a reason you're using the raw device
instead of the drbd device when drbd is loaded? ...and does the drbd
device show the same degradation? 

On Thu, 2007-03-29 at 12:46 -0500, Duane Cox wrote:
> >
> > ./dm -a 0 -b 1M -s 3G -y -m -p -o /dev/sdb
> > 71.87 MB/sec (3221225472 B / 00:42.745236)
> > 
> > ...
> > 
> > ./dm -a 0 -b 1M -s 3G -y -m -p -o /dev/sdb
> > 33.47 MB/sec (3221225472 B / 01:31.781341)
> >
> >
> now I removed the module by running /etc/init.d/drbd stop
> lsmod shows drbd was indeed removed....
> 
> ./dm -a 0 -b 1M -s 3G -y -m -p -o /dev/sdb
> 71.99 MB/sec (3221225472 B / 00:42.672736)
> 
> ./dm -a 0 -b 1M -s 3G -y -m -p -o /dev/sdb
> 71.39 MB/sec (3221225472 B / 00:43.029786)
> 
> ./dm -a 0 -b 1M -s 3G -y -m -p -o /dev/sdb
> 72.55 MB/sec (3221225472 B / 00:42.341708)
> 
> 
> tried MULTIPLE times on two identical pieces of hardware, and get the same
> results: stable, consistent write throughput.
> 
> so in summary, with the drbd module loaded (nd in disconnected state even),
> write performance to the raw block device degrades over time...
> 
> Thanks
> Duane Cox
> 
> 
> 
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