When DRBD 8.4.4 integrated TRIM/Discard support, a lot of things got much better… for example, 700MB/sec over a 1GBit/sec connection.
As described in the Root-on-DRBD tech guide, my notebook uses DRBD on top of an SSD; apart from the IO speed, the other important thing is the Trim/Discard support.
In practice that means, e.g., that the resync goes much faster: most of the blocks that were written while being off-site have already been discarded again, and so the automatical
fstrim can drop the needed amount of data by “up to” 100%.
Result: with a single SSD on one end, 1GBit network connectivity, and thin LVM on top of a 2-harddisk RAID1 on the other end, a resync rate of 700MB/sec!
Here are the log lines, heavily shortened so that they’re readable; starting at 09:39:00:
At 09:40:27 the resync concludes; the first line is the relevant one:
block drbd9: Resync done (total 87 sec; paused 0 sec; 707256 K/sec) block drbd9: updated UUIDs 7:0:4:4 block drbd9: conn( SyncSource -> Connected ) pdsk( Inc -> UpToDate )
That’s how it’s done 😉