swapping LVs about

Gabriel M Dragffy dragffy at yandex.ru
Sun Sep 3 20:32:08 UTC 2006


I don't understand quite exactly. Am I right in thinking that if I
create a snapshot volume it will gradually grow larger as I make changes
to the volume it is partitioning? In this case how do I know when the
snapshot volume it running out of space? And also doesn't this affect
performance since you are simultaneously writing changes to a volume and
it's snapshot...?

On Sun, 2006-09-03 at 14:40 +0200, Alexander Skwar wrote:
> · Gabriel M Dragffy <dragffy at yandex.ru>:
> 
> > I also have something that I don't understand. My root partition is 300M
> > and has used about 170M of space. I created a 100M snapshot volume of it
> > and it worked - how come it had enough space? How much space does a
> > snapshot actually need,
> 
> 0 - zero
> 
> > or more simply how does the snapshot work?
> 
> When you create a snapshot volume, you take, well..., a snapshot
> of the volume. This means, at a later time, you can see how the
> volume looked like at the moment, when you took the snapshot.
> 
> Now, to do so, if something gets written to the original LV, LVM
> needs to somehow note the differences. And that's where the size
> of the snapshot LV comes into play. If you've got a 100M snapshot
> LV, you'll be able to write up to 100M to the original LV. After
> that, the Snapshot LV is full.
> 
> Alexander Skwar
> -- 
> I waited and waited and when no message came I knew it must be from you.
> 
> 
> 





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