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Diffstat (limited to 'Documentation/device-mapper/snapshot.txt')
| -rw-r--r-- | Documentation/device-mapper/snapshot.txt | 16 |
1 files changed, 16 insertions, 0 deletions
diff --git a/Documentation/device-mapper/snapshot.txt b/Documentation/device-mapper/snapshot.txt index b8bbb516f989..1810833f6dc6 100644 --- a/Documentation/device-mapper/snapshot.txt +++ b/Documentation/device-mapper/snapshot.txt @@ -31,6 +31,7 @@ its visible content unchanged, at least until the <COW device> fills up. *) snapshot <origin> <COW device> <persistent?> <chunksize> + [<# feature args> [<arg>]*] A snapshot of the <origin> block device is created. Changed chunks of <chunksize> sectors will be stored on the <COW device>. Writes will @@ -53,8 +54,23 @@ When loading or unloading the snapshot target, the corresponding snapshot-origin or snapshot-merge target must be suspended. A failure to suspend the origin target could result in data corruption. +Optional features: + + discard_zeroes_cow - a discard issued to the snapshot device that + maps to entire chunks to will zero the corresponding exception(s) in + the snapshot's exception store. + + discard_passdown_origin - a discard to the snapshot device is passed + down to the snapshot-origin's underlying device. This doesn't cause + copy-out to the snapshot exception store because the snapshot-origin + target is bypassed. + + The discard_passdown_origin feature depends on the discard_zeroes_cow + feature being enabled. + * snapshot-merge <origin> <COW device> <persistent> <chunksize> + [<# feature args> [<arg>]*] takes the same table arguments as the snapshot target except it only works with persistent snapshots. This target assumes the role of the |