Commit 411f1140 authored by Paolo 'Blaisorblade' Giarrusso's avatar Paolo 'Blaisorblade' Giarrusso Committed by Linus Torvalds

[PATCH] Fix dm-snapshot tutorial in Documentation

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 <>
Signed-off-by: default avatarPaolo 'Blaisorblade' Giarrusso <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent f73195ad
......@@ -19,7 +19,6 @@ There are two dm targets available: snapshot and snapshot-origin.
*) snapshot-origin <origin>
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
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.
......@@ -27,7 +26,7 @@ its visible content unchanged, at least until the <COW device> fills up.
*) 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
only go to the <COW device>. Reads will come from the <COW device> or
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
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
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