On 03/16/12 4:10 PM, ken wrote: > Thanks, Les! That fleshes the process out a little more for me. But > what does it mean that a snapshot is "active"? means one exists. LVM maps logical volumes (LV) onto a set of PP (physical partitions, also called extents) that are maybe 4-16MB each (this is configurable when you create the partition). when you create a snapshot, nothing actually happens until the file system is written, the snapshot is just another view of the PPs assembled into a new LV thats pointing to the same blocks... when the original LV is written, the existing data is copied to new PP's grabbed from the free pool, and the snapshot is pointed at these saved copies, then the file system is allowed to write onto the original PPs. when you delete the snapshot these new PPs containing the original data are lost. if you revert the file system to the snapshot, then the PPs that were updated are deleted and the snapshot becomes the LV. the implementation of this in Linux came from IBM's AIX Unix, where the Logical Volume Manager is quite nicely integrated with their JVM/JVM2 file systems (grow the file system and the LV's are expanded automatically). -- john r pierce N 37, W 122 santa cruz ca mid-left coast