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

Bart Coninckx bart.coninckx at telenet.be
Mon Oct 20 16:11:56 CEST 2008


> > > fix your local io subsystem.
> > > fix your local io subsystem driver.
> > >
> > > check
> > >  local io subsystem,
> > >  (battery backed) write cache enabled?
> >
> > Yes, I did that yesterday, I got from 13 MB/Sec to 16 MB/Sec. Better, but
> > still not good.
> >
> > >  raid resync/rebuild/re-whatever going on at the same time?
> >
> > nope, RAID has been built and is steady.
> >
> > >  does the driver honor BIO_RW_SYNC?
> >
> > errr ... how can I check that? /proc/driver/cciss/cciss0 does not reveal
> > anything about that.
> >
> > >  does the driver introduce additional latency
> > >  because of ill-advised "optimizations"?
> >
> > I use a stock SLES 10 SP1 cciss driver. I did understand that the I/O
> > scheduler is not the best one. Perhaps you are referring to that?
> >
> > > if local io subsystem is ok,
> > > but DRBD costs more than a few percent in throughput,
> > > check your local io subsystem on the other node!
> >
> > That node is identical to the other one.
> >
> > > if that is ok as well, check network for throughput,
> > > latency and packet loss/retransmits.
> >
> > scp gives me about 70 MB/Sec, so my guess is that things are more likely
> > related to drbd and local io.
>
> scp does not know about fsync.
>
> use the same benchmark against drbd and non-drbd partition on that cciss...
>
> > > only if all of that seems ok too,
> > > check drbd configuration.
> > >
> > > > > Of course, I am inclined to advise an upgrade to SP2, which might
> > > > > help with a newer cciss driver ;-)
> > >
> > > a-ha.
> >
> > since I use OES2 which is not supported on SP2, I'm somewhat reluctant on
> > installing the kernel from SP2. Novell support will most likely be gone
> > when I do this ...

All,

I updated the cciss-driver from 3.6.14 to 3.6.18-17. Unfortunately this didn't 
get me any better results. So this is not related to driver issues I guess. 

Next I will try to change the I/O scheduler. Any other suggestions?


Thx,

B.



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