tail -f /var/log/dmesg

[526517.668034] block drbd4: role( Primary -> Secondary )
[526517.668222] block drbd4: bitmap WRITE of 0 pages took 0 jiffies
[526517.682183] block drbd4: 0 KB (0 bits) marked out-of-sync by on disk bit-map.
[526529.713201] block drbd4: peer( Primary -> Unknown ) conn( Connected -> Disconnecting ) pdsk( UpToDate -> DUnknown )
[526529.713341] block drbd4: asender terminated
[526529.713353] block drbd4: Terminating drbd4_asender
[526529.742751] block drbd4: Connection closed
[526529.742823] block drbd4: conn( Disconnecting -> StandAlone )
[526529.742904] block drbd4: receiver terminated
[526529.742911] block drbd4: Terminating drbd4_receiver
[526529.743030] block drbd4: disk( UpToDate -> Failed )
[526529.743081] block drbd4: Sending state for detaching disk failed
[526529.743149] block drbd4: disk( Failed -> Diskless )
[526529.743198] block drbd4: drbd_bm_resize called with capacity == 0
[526529.743415] block drbd4: worker terminated
[526529.743422] block drbd4: Terminating drbd4_worker
[526530.803882] block drbd4: Starting worker thread (from drbdsetup [20762])
[526530.804362] block drbd4: disk( Diskless -> Attaching )
[526530.805705] block drbd4: Found 4 transactions (21 active extents) in activity log.
[526530.805714] block drbd4: Method to ensure write ordering: flush
[526530.805725] block drbd4: drbd_bm_resize called with capacity == 65009656
[526530.807169] block drbd4: resync bitmap: bits=8126207 words=126972 pages=248
[526530.807179] block drbd4: size = 31 GB (32504828 KB)
[526530.834342] block drbd4: bitmap READ of 248 pages took 7 jiffies
[526530.837273] block drbd4: recounting of set bits took additional 1 jiffies
[526530.837282] block drbd4: 0 KB (0 bits) marked out-of-sync by on disk bit-map.
[526530.837297] block drbd4: disk( Attaching -> UpToDate )
[526530.837304] block drbd4: attached to UUIDs 94222F9BB3BB1E26:0000000000000000:BBCC3322C4784787:BBCB3322C4784787
[526530.923853] block drbd4: conn( StandAlone -> Unconnected )
[526530.923915] block drbd4: Starting receiver thread (from drbd4_worker [20763])
[526530.924160] block drbd4: receiver (re)started
[526530.924181] block drbd4: conn( Unconnected -> WFConnection )
[526531.421999] block drbd4: Handshake successful: Agreed network protocol version 96
[526531.422016] block drbd4: conn( WFConnection -> WFReportParams )
[526531.422134] block drbd4: Starting asender thread (from drbd4_receiver [20777])
[526531.424941] block drbd4: data-integrity-alg: sha1
[526531.425157] block drbd4: drbd_sync_handshake:
[526531.425170] block drbd4: self 94222F9BB3BB1E26:0000000000000000:BBCC3322C4784787:BBCB3322C4784787 bits:0 flags:0
[526531.425184] block drbd4: peer CC8966C497399DDB:94222F9BB3BB1E27:BBCC3322C4784786:BBCB3322C4784787 bits:0 flags:0
[526531.425196] block drbd4: uuid_compare()=-1 by rule 50
[526531.425218] block drbd4: peer( Unknown -> Primary ) conn( WFReportParams -> WFBitMapT ) disk( UpToDate -> Outdated ) pdsk( DUnknown -> UpToDate )
[526531.483843] block drbd4: conn( WFBitMapT -> WFSyncUUID )
[526531.524843] block drbd4: updated sync uuid 94232F9BB3BB1E26:0000000000000000:BBCC3322C4784787:BBCB3322C4784787
[526531.542990] block drbd4: helper command: /sbin/drbdadm before-resync-target minor-4
[526531.558092] block drbd4: helper command: /sbin/drbdadm before-resync-target minor-4 exit code 0 (0x0)
[526531.558111] block drbd4: conn( WFSyncUUID -> SyncTarget ) disk( Outdated -> Inconsistent )
[526531.558139] block drbd4: Began resync as SyncTarget (will sync 0 KB [0 bits set]).
[526531.560816] block drbd4: Resync done (total 1 sec; paused 0 sec; 0 K/sec)
[526531.560837] block drbd4: updated UUIDs CC8966C497399DDA:0000000000000000:94232F9BB3BB1E26:94222F9BB3BB1E27
[526531.560856] block drbd4: conn( SyncTarget -> Connected ) disk( Inconsistent -> UpToDate )
[526531.584595] block drbd4: helper command: /sbin/drbdadm after-resync-target minor-4
[526531.598872] block drbd4: helper command: /sbin/drbdadm after-resync-target minor-4 exit code 0 (0x0)
[526531.604548] block drbd4: bitmap WRITE of 248 pages took 2 jiffies
[526531.617608] block drbd4: 0 KB (0 bits) marked out-of-sync by on disk bit-map.
[526531.898085] block drbd4: role( Secondary -> Primary )