--On July 7, 2006 2:35:23 AM -0700 "Joe Donner (sent by Nabble.com)" <[EMAIL PROTECTED]> wrote:
Does anyone use or have knowledge of using LVM snapshots with Amanda backups? I believe it to be the same concept as Shadow Volume Copies in Windows 2003, and that is quite useful. A little bit of info here: http://arstechnica.com/articles/columns/linux/linux-20041013.ars I'm just wondering what happens during the freeze - how freezing "all activity to and from the filesystem to reduce the risk of problems" affects the system? One would imagine that disk writes are somehow queued up and complete when the file system is unfreezed again?
It's only stopped long enough to make the bitmap table. After that it's Copy On Write. Meaning a snapshot is free until the 'original' starts to differ then the snapshot starts to take up space because you have to make copies of the original blocks for the snapshot once they start to change.
In 2.4 atleast though LVM snapshots are extremely limited. The kernel has to find a contiguous section of RAM to put the bitmap table of COW pages in. If you've a significantly sized LVM LV you won't be able to snapshot it even reliably.
A better place to ask how does LVM work would be one of the LVM discussion groups.
Here's a couple helpful links. <http://tldp.org/HOWTO/LVM-HOWTO/lvm2faq.html> <http://www.tldp.org/HOWTO/LVM-HOWTO/>
Joe -- View this message in context: http://www.nabble.com/LVM-snapshots-tf1905387.html#a5214340 Sent from the Amanda - Users forum at Nabble.com.
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