From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Bryn M. Reeves" <bmr@redhat.com>
Subject: Re: "create snapshots of any block device"
Date: Tue, 22 Jan 2013 11:22:27 +0000
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Cc: Hauke Laging <mailinglisten@hauke-laging.de>
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On 01/22/2013 11:12 AM, Hauke Laging wrote:
> Isn't that at least misleading? Is it really possible to create a snapshot of
> e.g. /dev/sda5 without creating an *additional* device as snapshot origin?

It's possible but as you note you have to create the dm layers for the 
snapshot. This means that if a non-dm device is in use you have to shut 
its users down (unmount file systems etc.), create the snapshot and then 
re-mount.

I've frequently used this in the past to snapshot large zero targets to 
create sparse devices for testing (before --virtualsize was added to LVM2).

With device-mapper devices this is unnecessary since the top-level 
device may be suspended while the snapshot layers are inserted.

Regards,
Bryn.