Derivative snapshots

Mike Young <myoung@wildernessvoice.com> · Thu, 24 Mar 2011 09:22:04 -0600

Hi,
I'd like to say in advance that I really appreciate any guidance/help I can receive with this request.

I am looking for a way to perform a derivative snapshot (i.e., a snapshot of an existing snapshot volume). I understand that there can be issues with respect to restoring an Original volume from such a derivative, and I'd like to say that I have no intention of any such restoration.

Basically, I want to use lvm to quickly generate a 100% block replica of an existing LV.

For example:
To create first snapshot
 lvcreate -L[same size as original] -sn [snapshot_1] /dev/[path to original]

After some time, I make a number of changes to the snapshot volume and I wish to replicate off of that.
lvcreate -L[same size as snapshot_1] -sn [snapshot_2] /dev/[path to snapshot_1]

When I try to create the derivative snapshot, I get the message "Snapshots of snapshots are not supported yet."

I can see how lvcreate validates the various arguments, but I'm not immediately seeing how this particular check is performed where it looks at the "type" of the source volume.

Can someone help me with where this check is actually performed?

Thanks,

Mike
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