[linux-lvm] meaning of -L for snapshots ?

[kelsey hudson]

Olivier Kaloudoff wrote:

>     Who can explain the usage of -L10M for my snapshot ?

LVM snapshots have a limitation to how much data can change before the 
snapshot becomes invalid. So, by using -L10M, you're saying to keep the 
snapshot around until 10M of data has changed, then the snapshot becomes 
invalid.

Because of the way LVM snapshots work, they require extra space on a 
volume. So, the size of your snapshot volume dictates how long it will 
remain valid. A good rule of thumb is between 10% and 20% of your 
primary volume's size. That way, 10 to 20% of the filesystem's contents 
can change and your snapshot will remain valid.

Hope this clears some things up for you.

-Kelsey