WinDRBD's progress is only visible when syncing. But I'd like to know how far has gone if the out-of-sync remains.
drbdsetup status foo --v --s
Through the detail view command, the following contents were obtained.
foo node-id:2 role:Primary suspended:no
write-ordering:flush
volume:1 minor:1 disk:UpToDate backing_dev:\DosDevices\G: quorum:yes
size:524253532 read:7238338 written:5209825 al-writes:589 bm-writes:198 upper-pending:0 lower-pending:10
al-suspended:no blocked:no
Node1 node-id:1 connection:Connected role:Secondary congested:no ap-in-flight:0 rs-in-flight:7168
volume:1 replication:SyncSource peer-disk:Inconsistent done:85.32 resync-suspended:no
received:0 sent:1226764 out-of-sync:210484 pending:6 unacked:10 dbdt1:14.99 eta:14
done:85.32
This part is known as the progress rate.
How was this calculated?
When a resource becomes disconnected, the out-of-sync counter will begin to increment on the peer that is currently Primary. When the resource reconnects, the bitmaps (stored in DRBD's metadata) are compared to determine which blocks became out-of-sync while disconnected, and proceeds to resync those blocks in the background. Any writes that occur during a background resync are immediately replicated, and if that write happens to touch a block that's a part of the background resync, it's removed from the resync queue (since it was updated by the foreground replication).