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-rw-r--r--Documentation/device-mapper/dm-raid.txt44
1 files changed, 37 insertions, 7 deletions
diff --git a/Documentation/device-mapper/dm-raid.txt b/Documentation/device-mapper/dm-raid.txt
index 56fb62b09fc5..b428556197c9 100644
--- a/Documentation/device-mapper/dm-raid.txt
+++ b/Documentation/device-mapper/dm-raid.txt
@@ -30,6 +30,7 @@ The target is named "raid" and it accepts the following parameters:
raid10 Various RAID10 inspired algorithms chosen by additional params
- RAID10: Striped Mirrors (aka 'Striping on top of mirrors')
- RAID1E: Integrated Adjacent Stripe Mirroring
+ - RAID1E: Integrated Offset Stripe Mirroring
- and other similar RAID10 variants
Reference: Chapter 4 of
@@ -64,15 +65,15 @@ The target is named "raid" and it accepts the following parameters:
synchronisation state for each region.
[raid10_copies <# copies>]
- [raid10_format near]
+ [raid10_format <near|far|offset>]
These two options are used to alter the default layout of
a RAID10 configuration. The number of copies is can be
- specified, but the default is 2. There are other variations
- to how the copies are laid down - the default and only current
- option is "near". Near copies are what most people think of
- with respect to mirroring. If these options are left
- unspecified, or 'raid10_copies 2' and/or 'raid10_format near'
- are given, then the layouts for 2, 3 and 4 devices are:
+ specified, but the default is 2. There are also three
+ variations to how the copies are laid down - the default
+ is "near". Near copies are what most people think of with
+ respect to mirroring. If these options are left unspecified,
+ or 'raid10_copies 2' and/or 'raid10_format near' are given,
+ then the layouts for 2, 3 and 4 devices are:
2 drives 3 drives 4 drives
-------- ---------- --------------
A1 A1 A1 A1 A2 A1 A1 A2 A2
@@ -85,6 +86,33 @@ The target is named "raid" and it accepts the following parameters:
3-device layout is what might be called a 'RAID1E - Integrated
Adjacent Stripe Mirroring'.
+ If 'raid10_copies 2' and 'raid10_format far', then the layouts
+ for 2, 3 and 4 devices are:
+ 2 drives 3 drives 4 drives
+ -------- -------------- --------------------
+ A1 A2 A1 A2 A3 A1 A2 A3 A4
+ A3 A4 A4 A5 A6 A5 A6 A7 A8
+ A5 A6 A7 A8 A9 A9 A10 A11 A12
+ .. .. .. .. .. .. .. .. ..
+ A2 A1 A3 A1 A2 A2 A1 A4 A3
+ A4 A3 A6 A4 A5 A6 A5 A8 A7
+ A6 A5 A9 A7 A8 A10 A9 A12 A11
+ .. .. .. .. .. .. .. .. ..
+
+ If 'raid10_copies 2' and 'raid10_format offset', then the
+ layouts for 2, 3 and 4 devices are:
+ 2 drives 3 drives 4 drives
+ -------- ------------ -----------------
+ A1 A2 A1 A2 A3 A1 A2 A3 A4
+ A2 A1 A3 A1 A2 A2 A1 A4 A3
+ A3 A4 A4 A5 A6 A5 A6 A7 A8
+ A4 A3 A6 A4 A5 A6 A5 A8 A7
+ A5 A6 A7 A8 A9 A9 A10 A11 A12
+ A6 A5 A9 A7 A8 A10 A9 A12 A11
+ .. .. .. .. .. .. .. .. ..
+ Here we see layouts closely akin to 'RAID1E - Integrated
+ Offset Stripe Mirroring'.
+
<#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
@@ -142,3 +170,5 @@ Version History
1.3.0 Added support for RAID 10
1.3.1 Allow device replacement/rebuild for RAID 10
1.3.2 Fix/improve redundancy checking for RAID10
+1.4.0 Non-functional change. Removes arg from mapping function.
+1.4.1 Add RAID10 "far" and "offset" algorithm support.