[lvm-devel] lvcreate -s - why specifying size for snapshot ?

[Dave Wysochanski]

On Fri, 2009-03-20 at 21:17 +0530, Sandeep K Sinha wrote:
> Hi all,
> Disk
> After hunting for relevant documents and failing to find one.
> I would like to know if its not true that the size of the snapshot
> should be equal to the original volume?
> If so, then why do we accept size for a snapshot?
> 
> Or Am I missing something somewhere else?
> 

The size for the snapshot is the exception store - basically the blocks
that get modified need some place to be stored.  This is why you need a
separate size for snapshot LV which may be very different (usually much
smaller) than the original LV.