[CentOS] DRBD very slow....

> Invest in a HW RAID card with NVRAM cache that will negate the need
> for barrier writes from the OS as the controller will issue them async
> from cache allowing I/O to continue flowing. This really is the safest
> method.
It's a better way. But socket oprions in DRBD up to 8.2 (Nagel alghoritm) 
can decrease performance in large amount of small syncronius writes.