From mboxrd@z Thu Jan  1 00:00:00 1970
From: Hauke Laging <mailinglisten@hauke-laging.de>
Subject: "create snapshots of any block device"
Date: Tue, 22 Jan 2013 12:12:58 +0100
Message-ID: <1766138.NkjTPulnJa@inno>
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Hello,

I am a bit surprised to read this:
"Device-mapper allows you, without massive data copying:

*) To create snapshots of any block device [...]"

here:
http://www.kernel.org/doc/Documentation/device-mapper/snapshot.txt

Isn't that at least misleading? Is it really possible to create a snaps=
hot of=20
e.g. /dev/sda5 without creating an *additional* device as snapshot orig=
in?


I export LVs to a VM where they appear as regular disks so that I canno=
t use =20
LVMs snapshot integration. Thus I create a dm device with a linear mapp=
ing to=20
each of these disks and mount the dm device, not the disk.

I just had the idea to create these dm layer devices as snapshot-origin=
s from=20
the start (instead of loading this target when a snapshot is really goi=
ng to=20
be created). Is there anything to be said against this? Is there any re=
ason at=20
all to use linear instead of snapshot-origin for devices with just one =
target=20
(except for possible confusion)?


Hauke
--=20
=E2=98=BA
PGP: 7D82 FB9F D25A 2CE4 5241 6C37 BF4B 8EEF 1A57 1DF5 (seit 2012-11-04=
)
http://www.openpgp-schulungen.de/

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