[DRBD-user] bonding more than two network cards still a bad idea?

Bart Coninckx bart.coninckx at telenet.be
Tue Oct 5 22:41:47 CEST 2010


On Tuesday 05 October 2010 15:31:56 J. Ryan Earl wrote:
> > Does your RAID controller have a power-backed write
> > 
> > > cache?
> > 
> > Yes
> 
> Then have you set:
> 
> disk {
>   [...]
>   no-disk-barrier;
>   no-disk-flushes;
>   no-disk-drain;
>   no-md-flushes;
> }

Now I will :-)

> > > Have you tried RAID10?
> > 
> > No, but since the bonnie++ test without DRBD give a 250 MB/sec
> > performance hit, I guess this is not where our bottleneck is ...
> 
> Is your metadata internal?  Without DRBD you don't have DRBD's metadata. 
> If the metadata is being written with FUA (Force Unit Access) method,
> sometimes it skips even battery-backed caches and issues an write.  Which
> on RAID<456> this equals additional reads/writes on drives to complete the
> strip line. Such contention can lower performance.  This is common with
> all journals and transaction logs, but it depends on your hardware's FUA
> implementation.
> 
> -JR

The metadata is indeed internal. I need to look into the FUA part of the 
controller specs, but I will start by implementing your other ideas first. 
Since netperf gives me almost the theoretical maximum and the backend storage 
scores highly, I suspect the culprit will mostly be a poorly configured 
drbd.conf. Next I will attack TCP tuning.

Will report back on this list on Thursday. 

Thx again!


B.


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