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[PATCH] Fix dm-snapshot tutorial in Documentation

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I've recently added this documentation, Alasdair gave some corrections, and
here are some further corrections on top of his work (partly style issue,
partly a technical error due to different past experience, partly a note
which I've added - i.e.  transient snapshots are lighter).

Cc: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Paolo 'Blaisorblade' Giarrusso 2005-11-07 01:01:01 -08:00 • committed by Linus Torvalds
parent f73195ad7e
commit 411f11405c
1 changed files with 3 additions and 2 deletions

5
Documentation/device-mapper/snapshot.txt
View file

@ -19,7 +19,6 @@ There are two dm targets available: snapshot and snapshot-origin.
*) snapshot-origin <origin> *) snapshot-origin <origin>
which will normally have one or more snapshots based on it. which will normally have one or more snapshots based on it.
You must create the snapshot-origin device before you can create snapshots.
Reads will be mapped directly to the backing device. For each write, the Reads will be mapped directly to the backing device. For each write, the
original data will be saved in the <COW device> of each snapshot to keep original data will be saved in the <COW device> of each snapshot to keep
its visible content unchanged, at least until the <COW device> fills up. its visible content unchanged, at least until the <COW device> fills up.
@ -27,7 +26,7 @@ its visible content unchanged, at least until the <COW device> fills up.
*) snapshot <origin> <COW device> <persistent?> <chunksize> *) snapshot <origin> <COW device> <persistent?> <chunksize>
A snapshot is created of the <origin> block device. Changed chunks of A snapshot of the <origin> block device is created. Changed chunks of
<chunksize> sectors will be stored on the <COW device>. Writes will <chunksize> sectors will be stored on the <COW device>. Writes will
only go to the <COW device>. Reads will come from the <COW device> or only go to the <COW device>. Reads will come from the <COW device> or
from <origin> for unchanged data. <COW device> will often be from <origin> for unchanged data. <COW device> will often be
@ -37,6 +36,8 @@ the amount of free space and expand the <COW device> before it fills up.
<persistent?> is P (Persistent) or N (Not persistent - will not survive <persistent?> is P (Persistent) or N (Not persistent - will not survive
after reboot). after reboot).
The difference is that for transient snapshots less metadata must be
saved on disk - they can be kept in memory by the kernel.
How this is used by LVM2 How this is used by LVM2