[linux-lvm] relocate on write for snapshot

Nils Juergens nils at muon.de
Fri Nov 19 17:19:33 UTC 2004

On Fri, 19.11.04, Ming Zhang <mingz at ele.uri.edu> wrote:

> instead of copy old one to snapshot, overwrite old one with new one, 2
> writes and 1 reads. it is possible that write new data to a usused
> location directly.

Since you have to delete the snapshot (and I don't think they live very long
on most systems) you don't gain anything (because you have copy the changes
back from the snapshot), but you make the cases of more than one snapshot
and (possibly) read-write snapshots a lot harder, maybe not in CPU or IO,
but certainly in code complexity, which is a thing you never do to gain
a bit of performance.

> i know later remove a snaphot will be a little trouble, but there must
> be some way to get around it.

Yes, you have to do the work you saved a couple of minutes earlier :)

just my EUR 0.02,

Nils Juergens  | nils at muon.de | icq 7090774
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