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Jonathan Brassow 06-08-2011 10:13 PM

DM RAID: documentation updates
Updates to the dm-raid.txt documentation.

Add a little more information for some of the parameters of a dm-raid CTR table
and add a little more clarity to how parameters are printed when 'dmsetup table'
is issued.

Signed-off-by: Jonathan Brassow <>

Index: linux-2.6/Documentation/device-mapper/dm-raid.txt
================================================== =================
--- linux-2.6.orig/Documentation/device-mapper/dm-raid.txt
+++ linux-2.6/Documentation/device-mapper/dm-raid.txt
@@ -22,10 +22,15 @@ planned for the future.) The list of re
is the same for all the current raid types. The required parameters are
positional, while the optional parameters are given as key/value pairs.
The possible parameters are as follows:
- <chunk_size> Chunk size in sectors.
+ <chunk_size> Chunk size in sectors. This parameter is often called
+ "stripe size". It is the only required parameter and
+ must be the first parameter.
[[no]sync] Force/Prevent RAID initialization
[rebuild <idx>] Rebuild the drive indicated by the index
- [daemon_sleep <ms>] Time between bitmap daemon work to clear bits
+ [daemon_sleep <ms>] Time between bitmap daemon work to clear bits. A longer
+ time means less bitmap I/O, but potentially longer resync
+ time after a failure due to a less frequent clearing of
+ the bitmap.
[min_recovery_rate <kB/sec/disk>] Throttle RAID initialization
[max_recovery_rate <kB/sec/disk>] Throttle RAID initialization
[max_write_behind <sectors>] See '-write-behind=' (man mdadm)
@@ -55,9 +60,12 @@ Examples:
raid4 4 2048 min_recovery_rate 20 sync
5 - 8:17 - 8:33 - 8:49 - 8:65 - 8:81

-Performing a 'dmsetup table' should display the CTR table used to
-construct the mapping (with possible reordering of optional
+Performing a 'dmsetup table' will display the CTR table used to construct the
+mapping. The optional parameters will always be printed in the order listed
+above. "sync" or "nosync" will always be printed before the other arguments,
+for example. If the user passes in optional arguments in a different order,
+the results of 'dmsetup table' will differ from the CTR table used to construct
+the mapping.

Performing a 'dmsetup status' will yield information on the state and
health of the array. The output is as follows:

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