ceph-osd devices does not support bcache disks

[Aymen Frikha]

I configured bcache devices with MAAS using and SSD disk with 12 HDD.
When I deploy ceph-osd with osd-devices= /dev/bcache0 /dev/bcache1 /dev/bcache2 ... I have this error:

2016-11-17 23:02:09 INFO mon-relation-changed ceph-disk: Error: partition 1 for /dev/bcache0 does not appear to exist
2016-11-17 23:02:09 ERROR juju-log mon:60: Unable to initialize device: /dev/bcache0
2016-11-17 23:02:09 INFO mon-relation-changed Traceback (most recent call last):
2016-11-17 23:02:09 INFO mon-relation-changed File "/var/lib/juju/agents/unit-ceph-osd-0/charm/hooks/mon-relation-changed", line 517, in <module>
2016-11-17 23:02:09 INFO mon-relation-changed hooks.execute(sys.argv)
2016-11-17 23:02:09 INFO mon-relation-changed File "/var/lib/juju/agents/unit-ceph-osd-0/charm/hooks/charmhelpers/core/hookenv.py", line 715, in execute
2016-11-17 23:02:09 INFO mon-relation-changed self._hooks[hook_name]()
2016-11-17 23:02:09 INFO mon-relation-changed File "/var/lib/juju/agents/unit-ceph-osd-0/charm/hooks/mon-relation-changed", line 444, in mon_relation
2016-11-17 23:02:09 INFO mon-relation-changed prepare_disks_and_activate()
2016-11-17 23:02:09 INFO mon-relation-changed File "/var/lib/juju/agents/unit-ceph-osd-0/charm/hooks/mon-relation-changed", line 354, in prepare_disks_and_activate
2016-11-17 23:02:09 INFO mon-relation-changed config('osd-encrypt'))
2016-11-17 23:02:09 INFO mon-relation-changed File "lib/ceph/__init__.py", line 1149, in osdize
2016-11-17 23:02:09 INFO mon-relation-changed reformat_osd, ignore_errors, encrypt)
2016-11-17 23:02:09 INFO mon-relation-changed File "lib/ceph/__init__.py", line 1204, in osdize_dev
2016-11-17 23:02:09 INFO mon-relation-changed raise e
2016-11-17 23:02:09 INFO mon-relation-changed subprocess.CalledProcessError: Command '['ceph-disk', 'prepare', '--fs-type', u'xfs', '--zap-disk', u'/dev/bcache0', u'/dev/sda']' returned non-zero exit status 1
2016-11-17 23:02:09 ERROR juju.worker.uniter.operation runhook.go:107 hook "mon-relation-changed" failed: exit status 1

It seems that osd-charm does not support bcache devices.
The workaround that I found is to mount with MAAS every bcache device into /bcache directory:
/dev/bcache0 -> /bcache0
and I used this directories with osd-devices parameter of osd-charm:
osd-devices = /bcache0 /bcache1 /bcache2 ...

[James Page (james-page)]

See http://tracker.ceph.com/issues/13278