FreeNAS Code

Refactor automatic replication/snapshotting process:

- Decouple replication from snapshotting. This makes it possible for the
snapshotter to take snapshots while replication is in progress.
- Implement a set of locking mechanism to prevent parallel issue.
- Protect "held" snapshots from being destroyed, this includes the last
snapshot we have replicated for an incremental transfer, the in-progress
snapshots.
- Try harder to recover from failed transfers.

Instead of setting a hard-coded mountpoint, use altroot to enforce the
desired hierarchy.

Add a simple handler to ix-zfs so it handles migration on boot.

While I'm there also slightly restruct the code to reduce duplication.

report zvol size and forget about used/available

fix zfs detach

fix disk replacement (aware of device name changing)

set absolute path to smartctl

unlabel disk before glabel it for iscsi

fix lookup for rawuuid, it could get a label instead of device

do not use subprocess.wait(), it can deadlock if the child process generates enough output to a pipe such that it blocks waiting for the OS pipe buffer to accept more data

glabel real disk device extent