devices part of RAID should be skipped

[Andreas Hasenack]

2016-03-23 20:35:11 INFO install mkfs.xfs: cannot open /dev/sdb: Device or resource busy
2016-03-23 20:35:11 INFO install Traceback (most recent call last):
2016-03-23 20:35:11 INFO install File "/var/lib/juju/agents/unit-swift-storage-0/charm/hooks/install.real", line 178, in <module>
2016-03-23 20:35:11 INFO install main()
2016-03-23 20:35:11 INFO install File "/var/lib/juju/agents/unit-swift-storage-0/charm/hooks/install.real", line 170, in main
2016-03-23 20:35:11 INFO install hooks.execute(sys.argv)
2016-03-23 20:35:11 INFO install File "/var/lib/juju/agents/unit-swift-storage-0/charm/hooks/charmhelpers/core/hookenv.py", line 717, in execute
2016-03-23 20:35:11 INFO install self._hooks[hook_name]()
2016-03-23 20:35:11 INFO install File "/var/lib/juju/agents/unit-swift-storage-0/charm/hooks/install.real", line 70, in install
2016-03-23 20:35:11 INFO install setup_storage()
2016-03-23 20:35:11 INFO install File "/var/lib/juju/agents/unit-swift-storage-0/charm/hooks/lib/swift_storage_utils.py", line 257, in setup_storage
2016-03-23 20:35:11 INFO install mkfs_xfs(dev)
2016-03-23 20:35:11 INFO install File "/var/lib/juju/agents/unit-swift-storage-0/charm/hooks/lib/swift_storage_utils.py", line 249, in mkfs_xfs
2016-03-23 20:35:11 INFO install check_call(cmd)
2016-03-23 20:35:11 INFO install File "/usr/lib/python2.7/subprocess.py", line 540, in check_call
2016-03-23 20:35:11 INFO install raise CalledProcessError(retcode, cmd)
2016-03-23 20:35:11 INFO install subprocess.CalledProcessError: Command '['mkfs.xfs', '-f', '-i', 'size=1024', u'/dev/sdb']' returned non-zero exit status 1
2016-03-23 20:35:11 ERROR juju.worker.uniter.operation runhook.go:107 hook "install" failed: exit status 1

# cat /proc/mdstat
Personalities : [raid1] [linear] [multipath] [raid0] [raid6] [raid5] [raid4] [raid10]
md0 : active raid1 sdd[1] sdb[0]
      16768896 blocks super 1.2 [2/2] [UU]

unused devices: <none>

The ceph-osd charm is already a bit smarter. For example:

2016-03-23 20:48:07 INFO mon-relation-changed ceph-disk: Error: Device /dev/sdd is in use by a device-mapper mapping (dm-crypt?): md0

We should do the same for swift-storage.