Backups stop whilst running

[Steve Bonnett]

When using bluestore osds, the backup data stops flowing, the task shows running, but no more data moves. I've swapped all the osds back to file and the backups work perfectly. Also backups stop if there is any osd using bluestore.

Syslog: only errors reported:
Sep 24 22:58:35 proxmox3 ceph-osd[2801487]: 2018-09-24 22:58:35.631428 7fb9fc2ba700 -1 log_channel(cluster) log [ERR] : 8.cf shard 1: soid 8:f322ac31:::1000000c7ce.00000042:head candidate had a read error
Sep 24 22:58:57 proxmox3 ceph-osd[2801487]: 2018-09-24 22:58:57.853020 7fb9fc2ba700 -1 log_channel(cluster) log [ERR] : 8.cf shard 1: soid 8:f343ce8d:::10000044f82.0000032c:head candidate had a read error
Sep 24 22:59:33 proxmox3 ceph-osd[2801487]: 2018-09-24 22:59:33.814809 7fb9fc2ba700 -1 log_channel(cluster) log [ERR] : 8.cf shard 1: soid 8:f368e039:::1000004dfa0.00014e77:head candidate had a read error
Sep 24 22:59:50 proxmox3 ceph-osd[2801487]: 2018-09-24 22:59:50.188754 7fb9fc2ba700 -1 log_channel(cluster) log [ERR] : 8.cf deep-scrub 0 missing, 3 inconsistent objects
Sep 24 22:59:50 proxmox3 ceph-osd[2801487]: 2018-09-24 22:59:50.188763 7fb9fc2ba700 -1 log_channel(cluster) log [ERR] : 8.cf deep-scrub 3 errors