[linux-lvm] CoW under the hood
zkabelac at redhat.com
Mon Dec 3 11:39:15 UTC 2018
Dne 03. 12. 18 v 7:17 Far Had napsal(a):
> I'm trying to understand how LVM thick snapshots work under the hood. I can
> see that when new write requests are comming to the original volume that has a
> snapshot, the current contents of storage blocks copy to the snapshot space
> then the new data overwrites on the volume. No problem so far.
> the question is when I delete a file on a volume that has snapshot, the
> content is gone on the volume so the pointer which points from volume object
> to that certain blocks on the volume should now point to empty blocks. On the
> other hand I can see that the contents of deleted parts from the original
> volume did not copy to the snapshot space, meaning that the snapshot pointers
> that were pointing to that blocks on the original volume, still point that
> In other words the pointers from both snapshot and original volume are
> pointing to the same blocks on the storage media but they don't show the same
> contents when you mount them on the filesystem.
> Please enlighten me about this situation
I assume going through some info from this page might put some light into it:
In particular http://people.redhat.com/agk/talks/FOSDEM_2005/
from slide 15 there is some info about snapshots you might find useful.
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