[DRBD-user] Sensible maximum number of drbd devices

Michael Paesold mpaesold at gmx.at
Thu Apr 6 10:35:33 CEST 2006

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.


Ben wrote:
> For what it's worth, I'm doing exactly what you're looking to do right now 
> with a whopping 7 DRBD devices. My write performance stinks - I can only 
> sync at 4MB/sec before a CPU core becomes entirely busy in IO wait - but I 
> suspect that's due to some misconfiguration, and haven't had much time to 
> look into it.

Thanks for the bit of information.

4MB/sec initial re-sync? Or 4MB/sec write performance in dom0 or in domU? If 
its write performance in domU, you should look into scheduling 
configuration.

See for example this thread:
http://lists.xensource.com/archives/html/xen-users/2006-04/msg00115.html
Doing something like the mentioned 'xm sched-sedf 0 0 0 0 1 1' could help.

> Other than the write performance, using DRBD and xen with heartbeat is 
> really, really cool.

Did you also try with less drbd devices and measure performance?

Best Regards,
Michael Paesold 





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