Add ZFS support

TODO

@@ -13,12 +13,18 @@ This is the list of TODO items for SnapRAID.
 https://github.com/linuxhw/SMART
 https://github.com/linuxhw/EnterpriseDrive
 
+* Implement the use Shadow Copy in Windows for creating snapshots.
+See Jens's Windows script at:
+http://sourceforge.net/p/snapraid/discussion/1677233/thread/a1707211/
+https://sourceforge.net/p/snapraid/discussion/1677233/thread/5c9e670c/
+Note that a difference between Windows and Unix is that in Windows old snapshots
+are automatically deleted.
+
 * A "dependents" output option to [--test-fmt file|disk|path|dependents] for LIST.
 Example, snapraid LIST --test-fmt dependents >FileList_with_dependents.txt
 The goal is a filelist that, for every file, includes full paths to the dependent files
 on other data disks needed to repair that file (in addition to the parity data).
-
-I created a thread about it here: https://sourceforge.net/p/snapraid/discussion/1677233/thread/6e872fdae0/
+See: https://sourceforge.net/p/snapraid/discussion/1677233/thread/6e872fdae0/
 
 - Minor
 
@@ -212,17 +218,6 @@ splitting.
 the number of hash for each file to three.
 - No way to handle block import.
 
-* Create a filesystem snapshot at every sync, and use it in all the other commands
-automatically.
-At the next sync, drop the old snapshot and create a new one.
-This should help recovering, because we'll have the exact copy used by sync.
-This feature can be enabled with a specific option, and available
-in Windows using Shadow Copy, and in Linux using Btrfs, and in a generic
-Unix using ZFS.
-See Jens's Windows script at: http://sourceforge.net/p/snapraid/discussion/1677233/thread/a1707211/
-Note that a difference between Windows and Unix is that in Windows old snapshots
-are automatically deleted.
-
 * Checks if splitting hash/parity computation in 4K pages
 can improve speed in sync. That should increase cache locality,
 because we read the data two times for hash and parity,