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Commit 411f1140 authored by Paolo 'Blaisorblade' Giarrusso's avatar Paolo 'Blaisorblade' Giarrusso Committed by Linus Torvalds
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[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 <agk@redhat.com>
Signed-off-by: default avatarPaolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent f73195ad

Documentation/device-mapper/snapshot.txt

+3 −2
Original line number Diff line number Diff line
@@ -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