Sync speed is excellent, but resync is **very** bad

DRBD
1

Using drbd as provided by Debian 12 and the default disk and net settings in drbd.conf I see an excellent sync performance, but a resync is very bad. 40 MBytes/sec over a 2*10Gbit bonding interface (active-backup), even though the disks are idle and there isn’t even a file system mounted.

This is weird. IMU data consistency should be achieved as fast as possible, even if this slows down regular write performance. WTH does it wait for?

Is there some way to tell drbd to prioritize resync speed, or to get at least a comparable performance?

2

If I recall the defaults are just a bit conservative to be safe. It’s very easy for resync to completely congest the link with active foreground replication is also competing.

I wrote a series of old blog articles on how best to tune the resync controller some years ago. These have since been converted into Knowledgebase articles. Please see here for tips on how best to tune the resync controller: Tuning DRBD's Resync Controller