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

Bart Coninckx bart.coninckx at telenet.be
Tue Oct 21 11:14:52 CEST 2008


> On Sat, Oct 18, 2008 at 09:18:33PM +0200, Petersen, Joerg wrote:
> > Well, my experience is that 8.0.7 is the fastest DRDB...
> > Later Versions just got slower!
> > Try: no-disk-flushes
> > and: no-md-flushes
> > if you are using DRBD >= 8.0.13
> > Not completely same to 8.0.7 but near to it...
>
> to recommend a known buggy version for imagined performance reasons is
> not particular HA.
>
> > Hi Lars,
> >
> > I did these:
> >
> > node1:/opt # hdparm -t /dev/drbd0
> >
> > Do these tests make any sence?
>
> if you care for write performance,
> why are you doing read benchmarks?

These are the only benchmarks I know how to do on both DRBD and non-DRBD 
partitions without destroying data.

I actually care for both read and write performance obviously, since users 
will be both reading and writing I guess (file and mailserver). 

What I just did is copying a 2.5 GB file to different locations. Mind you, the 
file is on the same harddrive (on /). These are the results:


to ext3 filesystem on /dev/drbd0: 17MB/sec
to /opt (on the same LVM VG as drbd0): 20 MB/sec
to / (non LVM, non DRBD): 24 MB/sec

So it seems there is a slight performance drop for DRBD, but the overall 
performance is not that good. 

What is striking though, is that a scp to the other node results in a 
performance of about 60 MB/sec.

Is there any logical explanation for this? Is this because of my copy tests 
read and write to the same drive? Can this explain the drop from about 60 
MB/sec to about 20 MB/sec?

Thank you. 


Bart





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