Robert Milkowski
2010-Jul-30 23:25 UTC
[zfs-discuss] Fwd: Read-only ZFS pools [PSARC/2010/306 FastTrack timeout 08/06/2010]
fyi
-------- Original Message --------
Subject: Read-only ZFS pools [PSARC/2010/306 FastTrack timeout 08/06/2010]
Date: Fri, 30 Jul 2010 14:08:38 -0600
From: Tim Haley <tim.haley at oracle.com>
To: PSARC-ext at sun.com
CC: zfs-team at sun.com
I am sponsoring the following fast-track for George Wilson. This case
introduces the ability to import ZFS pools in a read-only mode.
Requested binding is micro/patch. Timeout is 8/6/2010.
Template Version: @(#)sac_nextcase 1.70 03/30/10 SMI
This information is Copyright (c) 2010, Oracle and/or its affiliates.
All rights reserved.
1. Introduction
1.1. Project/Component Working Name:
Read-only ZFS pools
1.2. Name of Document Author/Supplier:
Author: George Wilson
1.3 Date of This Document:
30 July, 2010
4. Technical Description
OVERVIEW:
When a ZFS pool is imported, all of its filesystems are mounted
and the
pool is imported in read-write mode. Although it''s possible
to mount
the individual filesystems in read-only mode during the import, the
pool continues to operate in a read-write fashion. This proposal
introduces new functionality which will allow the administrator to
better control how ZFS pools are imported.
PROPOSED SOLUTION:
This case introduces a new pool-level property,
''readonly'', and a
new command line flag for the ''zpool import''
sub-command.
The new pool-level property is a non-persistent property and
can only be set when importing a pool. The default value of
''readonly'' will be ''off''
(read-write) and can be overridden at
import
time to make the pool read-only.
# zpool import -o readonly=on tank
When the ''readonly'' property is
''on'' (read-only) the following
actions
are performed:
1). pool is loaded but transaction processing is disabled
2). all filesystems and zvols are mounted in read-only mode
3). any intent-log replays are deferred (any pending synchronous
writes will be replayed once the pool is imported read-write)
The following restrictions apply when a pool is read-only:
1). Attempts to set additional zpool-level properties during import
are ignored.
2). All filesystem mounts are converted to include the
''ro''
mount option.
3). Additional mount options may be set on a temporary basis.
A pool which has been imported read-only can be restored back
to read-write by exporting and reimporting it.
In addition, a new option, ''-N'', will be added to the
''zpool
import''
sub-command. This will provide the ability to import a pool but
prevents any filesystem from being mounted.
# zpool import -N tank
MANPAGE DIFFS:
zpool import [-o mntopts] [-p property=value] ... [-d dir | -c
cachefile]
- [-D] [-f] [-m] [-R root] [-F [-n]] -a
+ [-D] [-f] [-m] [-N] [-R root] [-F [-n]] -a
+ The following property can be set at import time:
+
+ readonly=on | off
+
+ Controls whether the pool can be modified. When enabled,
+ any synchronous data which exists only on the intent log
+ will not be accessible until the pool is re-imported in
+ read-write mode.
The following properties can be set at creation time and
import time, and later changed with the zpool set command:
zpool import [-o mntopts] [-o property=value] ... [-d dir | -c
cachefile]
- -c cachefile] [-D] [-f] [-m] [-R root] [-F [-n]] -a
+ -c cachefile] [-D] [-f] [-m] [-N] [-R root] [-F [-n]] -a
+ -N
+
+ Import the pool without mounting any file systems.
6. Resources and Schedule
6.4. Steering Committee requested information
6.4.1. Consolidation C-team Name:
ON
6.5. ARC review type: FastTrack
6.6. ARC Exposure: open
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