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-rw-r--r--Documentation/device-mapper/dm-raid.txt17
1 files changed, 17 insertions, 0 deletions
diff --git a/Documentation/device-mapper/dm-raid.txt b/Documentation/device-mapper/dm-raid.txt
index 5e3786fd9ea7..0d199353e477 100644
--- a/Documentation/device-mapper/dm-raid.txt
+++ b/Documentation/device-mapper/dm-raid.txt
@@ -161,6 +161,15 @@ The target is named "raid" and it accepts the following parameters:
the RAID type (i.e. the allocation algorithm) as well, e.g.
changing from raid5_ls to raid5_n.
+ [journal_dev <dev>]
+ This option adds a journal device to raid4/5/6 raid sets and
+ uses it to close the 'write hole' caused by the non-atomic updates
+ to the component devices which can cause data loss during recovery.
+ The journal device is used as writethrough thus causing writes to
+ be throttled versus non-journaled raid4/5/6 sets.
+ Takeover/reshape is not possible with a raid4/5/6 journal device;
+ it has to be deconfigured before requesting these.
+
<#raid_devs>: The number of devices composing the array.
Each device consists of two entries. The first is the device
containing the metadata (if any); the second is the one containing the
@@ -245,6 +254,9 @@ recovery. Here is a fuller description of the individual fields:
<data_offset> The current data offset to the start of the user data on
each component device of a raid set (see the respective
raid parameter to support out-of-place reshaping).
+ <journal_char> 'A' - active raid4/5/6 journal device.
+ 'D' - dead journal device.
+ '-' - no journal device.
Message Interface
@@ -314,3 +326,8 @@ Version History
1.9.0 Add support for RAID level takeover/reshape/region size
and set size reduction.
1.9.1 Fix activation of existing RAID 4/10 mapped devices
+1.9.2 Don't emit '- -' on the status table line in case the constructor
+ fails reading a superblock. Correctly emit 'maj:min1 maj:min2' and
+ 'D' on the status line. If '- -' is passed into the constructor, emit
+ '- -' on the table line and '-' as the status line health character.
+1.10.0 Add support for raid4/5/6 journal device