[linux-lvm] What happens with full snapshots

["Harald Heigl" <Harald_Heigl@gmx.at>]

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Hello,

I'm relatively new to lvm, I'm using Fedora for almost 3 years, but up to
now I just set up lvm on install, formatted my ext3/ext4 and it just works.

Now I want to go somehow deeper playing around with snapshots.

 

I know you should size your snapshot volume to a size that can hold all the
changes. As I see a snap lv only contains the "original" datachunks and the
original lv is in a normal state as if there were no snapshot. 

 

My questions:

1.       What happens if the snap gets full (e.g. someone copies large data
from one lv to a snapshotted lv or something other you didn't expect), some
sites say it original and snapshot gets deactivated, some sites say the snap
lv gets invalidated. What does this mean? Is my original volume just crap
afterwards or can I work on as usual (with the difference that nothing is
written on the snap anymore), or just need to remove the snap ..

2.       What happens if there is a problem with a snap? I've heard on
reboot the snapshots are lost. What if there is a power shortage, so the
snap is lost, you boot and the original lv just seeks for the snap? Are
there implications on this. Can you just mount such a original lv or do you
have to remove the (non existent) snap lv before (How can you remove a
snapshot that doesn't exist anymore)

 

That would be nice to know before I use snaps.

Thanks in advance,

Harald (Harry) Heigl

 


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