#Device Mapper Mirror Target

GSoC 2011
Adam Hoka

##Specification

Version 1

###Definitions
- DM: Device Mapper (see: http://sources.redhat.com/dm/)
- Volume: a DM's idea of the whole or the a part of a disk's storage area

###Requirements

1. The Mirror target should implement RAID 1.
2. Two or more volumes should be able to used within the mirror.
3. Removal of all but one volume should still produce a working volume.
4. Online removal of any volumes should keep the mirror working, given that there is still a working volume present.
5. Failure to any of the disks holding any of the volumes should not lead to data loss or corruption, given that one or more disks holding at least one of the mirrored volumes are still present and healthy.
6. The Mirror target's ioctl interface should be compatible with LVM Tools.
7. Any meta data stored on disk should be kept consistent across any possible unclean shutdown.