[linux-lvm] mirror and snapshot incompatible

Yoav ml-lvm at hidden.domain.name
Tue Oct 28 02:28:14 UTC 2008

According to lvcreate, a snapshot of a mirrored volume cannot be created 
("Snapshots and mirrors may not yet be mixed").  However, devmapper does 
not seem to have the same limitation when used directly (not through lvm).

Is there a current reason for lvcreate to enforce this rather harsh 

What are the risks I'm taking by manually creating a dm-snapshot from a 
dm-mirror device?  (of course I'm also replacing the dm-mirror device 
with a snapshot-origin of the actual dm-mirror device).

If there is an actual reason for preventing this, what is the suggested 
way to consistently backup a mirror volume?  Is there a way to 
temporarily take one of the mirror "legs" (mimage devices)  offline in 
order to back it up, and resync it later?


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