[Discuss] lvm snapshot cloning

[Richard Pieri]

On Oct 24, 2011, at 10:42 PM, markw at mohawksoft.com wrote:
> 
> I can't understand your perspective here. We have various RAID drivers, we
> have linear drivers, sparse volumes, encrypted volumes, and so on. All
> implemented at the block device level.

Then let me paraphrase it:  LVM is a logical partition manager.


> How are snapshots any more or less complex or problematic than a RAID5 or
> encrypted block device?

Practical example:  create your "master" volume (partition) with 1TB.  Create a snapshot of the master, call it "a" and give it 100GB.  Create another snapshot of the master, call it "b" and give it 1GB.  The snapshots are created such that a does COW against master and b is mostly pointers to volume a's blocks so that you don't have the duplicated blocks.

Now, delete volume a.  Or copy 100GB+1byte to volume a.  This will trigger LVM's reaper which prunes the snapshot to ensure that there is no data loss on master.

--Rich P.