I copy paste the log of the migration and I color in red the gap of 11s I observe.
root@kcl-node1:~# qm migrate 104 kcl-node2 --online --with-local-disks
2017-12-07 11:44:24 starting migration of VM 104 to node 'kcl-node2' (10.81.59.102)
2017-12-07 11:44:24 found local disk 'local-lvm:vm-104-disk-1' (in current VM config)
2017-12-07 11:44:24 copying disk images
2017-12-07 11:44:24 starting VM 104 on remote node 'kcl-node2'
2017-12-07 11:44:26 start remote tunnel
2017-12-07 11:44:26 ssh tunnel ver 1
2017-12-07 11:44:26 starting storage migration
2017-12-07 11:44:26 scsi0: start migration to to nbd:10.81.59.102:60000:exportname=drive-scsi0
drive mirror is starting for drive-scsi0
drive-scsi0: transferred: 0 bytes remaining: 5477761024 bytes total: 5477761024 bytes progression: 0.00 % busy: 1 ready: 0
drive-scsi0: transferred: 116391936 bytes remaining: 5361369088 bytes total: 5477761024 bytes progression: 2.12 % busy: 1 ready: 0
drive-scsi0: transferred: 225443840 bytes remaining: 5252317184 bytes total: 5477761024 bytes progression: 4.12 % busy: 1 ready: 0
drive-scsi0: transferred: 342884352 bytes remaining: 5134876672 bytes total: 5477761024 bytes progression: 6.26 % busy: 1 ready: 0
drive-scsi0: transferred: 457179136 bytes remaining: 5020581888 bytes total: 5477761024 bytes progression: 8.35 % busy: 1 ready: 0
drive-scsi0: transferred: 573571072 bytes remaining: 4904189952 bytes total: 5477761024 bytes progression: 10.47 % busy: 1 ready: 0
drive-scsi0: transferred: 691011584 bytes remaining: 4786749440 bytes total: 5477761024 bytes progression: 12. % busy: 1 ready: 0
drive-scsi0: transferred: 3783262208 bytes remaining: 1694564352 bytes total: 5477826560 bytes progression: 69.07 % busy: 1 ready: 0
drive-scsi0: transferred: 3900702720 bytes remaining: 1577123840 bytes total: 5477826560 bytes progression: 71.21 % busy: 1 ready: 0
drive-scsi0: transferred: 4017094656 bytes remaining: 1460731904 bytes total: 5477826560 bytes progression: 73.33 % busy: 1 ready: 0
drive-scsi0: transferred: 4133486592 bytes remaining: 1344339968 bytes total: 5477826560 bytes progression: 75.46 % busy: 1 ready: 0
drive-scsi0: transferred: 4250927104 bytes remaining: 1226899456 bytes total: 5477826560 bytes progression: 77.60 % busy: 1 ready: 0
drive-scsi0: transferred: 4367319040 bytes remaining: 1110507520 bytes total: 5477826560 bytes progression: 79.73 % busy: 1 ready: 0
drive-scsi0: transferred: 4483710976 bytes remaining: 994115584 bytes total: 5477826560 bytes progression: 81.85 % busy: 1 ready: 0
drive-scsi0: transferred: 4601151488 bytes remaining: 876675072 bytes total: 5477826560 bytes progression: 84.00 % busy: 1 ready: 0
drive-scsi0: transferred: 4717543424 bytes remaining: 760283136 bytes total: 5477826560 bytes progression: 86.12 % busy: 1 ready: 0
drive-scsi0: transferred: 4833935360 bytes remaining: 643956736 bytes total: 5477892096 bytes progression: 88.24 % busy: 1 ready: 0
drive-scsi0: transferred: 4951375872 bytes remaining: 526516224 bytes total: 5477892096 bytes progression: 90.39 % busy: 1 ready: 0
drive-scsi0: transferred: 5067767808 bytes remaining: 410124288 bytes total: 5477892096 bytes progression: 92.51 % busy: 1 ready: 0
drive-scsi0: transferred: 5183111168 bytes remaining: 294780928 bytes total: 5477892096 bytes progression: 94.62 % busy: 1 ready: 0
drive-scsi0: transferred: 5301600256 bytes remaining: 176291840 bytes total: 5477892096 bytes progression: 96.78 % busy: 1 ready: 0
drive-scsi0: transferred: 5416943616 bytes remaining: 60948480 bytes total: 5477892096 bytes progression: 98.89 % busy: 1 ready: 0
drive-scsi0: transferred: 5477892096 bytes remaining: 0 bytes total: 5477892096 bytes progression: 100.00 % busy: 0 ready: 1
all mirroring jobs are ready
2017-12-07 11:45:16 starting online/live migration on unix:/run/qemu-server/104.migrate
2017-12-07 11:45:16 migrate_set_speed: 8589934592
2017-12-07 11:45:16 migrate_set_downtime: 0.1
2017-12-07 11:45:16 set migration_caps
2017-12-07 11:45:16 set cachesize: 858993459
2017-12-07 11:45:16 start migrate command to unix:/run/qemu-server/104.migrate
2017-12-07 11:45:17 migration status: active (transferred 110599053, remaining 5645664256), total 8607571968)
2017-12-07 11:45:17 migration xbzrle cachesize: 536870912 transferred 0 pages 0 cachemiss 0 overflow 0
2017-12-07 11:45:18 migration status: active (transferred 227295041, remaining 5524242432), total 8607571968)
2017-12-07 11:45:18 migration xbzrle cachesize: 536870912 transferred 0 pages 0 cachemiss 0 overflow 0
2017-12-07 11:45:19 migration status: active (transferred 332378247, remaining 609148928), total 8607571968)
2017-12-07 11:45:19 migration xbzrle cachesize: 536870912 transferred 0 pages 0 cachemiss 0 overflow 0
2017-12-07 11:45:20 migration status: active (transferred 449122925, remaining 484204544), total 8607571968)
2017-12-07 11:45:20 migration xbzrle cachesize: 536870912 transferred 0 pages 0 cachemiss 0 overflow 0
2017-12-07 11:45:21 migration status: active (transferred 565772005, remaining 358039552), total 8607571968)
2017-12-07 11:45:21 migration xbzrle cachesize: 536870912 transferred 0 pages 0 cachemiss 0 overflow 0
2017-12-07 11:45:22 migration status: active (transferred 682510788, remaining 233914368), total 8607571968)
2017-12-07 11:45:22 migration xbzrle cachesize: 536870912 transferred 0 pages 0 cachemiss 0 overflow 0
2017-12-07 11:45:23 migration status: active (transferred 799100315, remaining 114352128), total 8607571968)
2017-12-07 11:45:23 migration xbzrle cachesize: 536870912 transferred 0 pages 0 cachemiss 0 overflow 0
2017-12-07 11:45:24 migration status: active (transferred 915795953, remaining 8859648), total 8607571968)
2017-12-07 11:45:24 migration xbzrle cachesize: 536870912 transferred 0 pages 0 cachemiss 4400 overflow 0
2017-12-07 11:45:24 migration speed: 141.24 MB/s - downtime 46 ms
2017-12-07 11:45:24 migration status: completed
drive-scsi0: transferred: 5477892096 bytes remaining: 0 bytes total: 5477892096 bytes progression: 100.00 % busy: 0 ready: 1
all mirroring jobs are ready
drive-scsi0: Completing block job...
drive-scsi0: Completed successfully.
drive-scsi0 : finished
Logical volume "vm-104-disk-1" successfully removed
2017-12-07 11:45:39 migration finished successfully (duration 00:01:16)
Between these two outputs there's the 11s gap. Any idea how can I reduce it without using shared storage?