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

Bart Coninckx bart.coninckx at telenet.be
Thu Oct 16 10:19:20 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.

> 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. 

> 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 ... 

thx again,


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