Tired of checking iotop and seeing that your drbd partition is using 99.99% of io all the time and finding your drbd device performs slow in general?
This is especially an issue in versions of DRBD in the 8.3 tree in particular one documented case is on "8.3.13" but it likely applies to other devices.
The symptoms are that resyncing is fine and normal but any reasonable amount of activity is very slow and lagged and creates a high server load and con........
I have not found the source of this but essentially it seems like drbd and ext4 may not play well but I have to confirm still.
In either case an older DRBD setup with older hard drives seems to have little to no iowait, but the main difference is the drbd partition is ext3 and not ext4. I will experiment and see if that fixes this, then we will know that DRBD and ext4 have issues.........