path: root/Documentation/device-mapper
diff options
authorAnton Arapov <>2012-10-29 11:15:37 +0100
committerAnton Arapov <>2012-10-29 11:15:37 +0100
commit7d558cd9c7b18e4b16953265aa0da45e63f3b968 (patch)
tree7135d5a810768c9c619346282ee9cfdf1765e225 /Documentation/device-mapper
parent985ef6b2108ed28ffd5f6630e1e0fce2e2a775f2 (diff)
fedora kernel: cd394142aac30b5c751f25b517572e2448695641v3.6.3-2f17
Signed-off-by: Anton Arapov <>
Diffstat (limited to 'Documentation/device-mapper')
3 files changed, 52 insertions, 5 deletions
diff --git a/Documentation/device-mapper/dm-raid.txt b/Documentation/device-mapper/dm-raid.txt
index 946c73342cd..1c184495716 100644
--- a/Documentation/device-mapper/dm-raid.txt
+++ b/Documentation/device-mapper/dm-raid.txt
@@ -27,6 +27,10 @@ The target is named "raid" and it accepts the following parameters:
- rotating parity N (right-to-left) with data restart
raid6_nc RAID6 N continue
- rotating parity N (right-to-left) with data continuation
+ raid10 Various RAID10 inspired algorithms chosen by additional params
+ - RAID10: Striped Mirrors (aka 'Striping on top of mirrors')
+ - RAID1E: Integrated Adjacent Stripe Mirroring
+ - and other similar RAID10 variants
Reference: Chapter 4 of
@@ -59,6 +63,28 @@ The target is named "raid" and it accepts the following parameters:
logical size of the array. The bitmap records the device
synchronisation state for each region.
+ [raid10_copies <# copies>]
+ [raid10_format near]
+ 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:
+ 2 drives 3 drives 4 drives
+ -------- ---------- --------------
+ A1 A1 A1 A1 A2 A1 A1 A2 A2
+ A2 A2 A2 A3 A3 A3 A3 A4 A4
+ A3 A3 A4 A4 A5 A5 A5 A6 A6
+ A4 A4 A5 A6 A6 A7 A7 A8 A8
+ .. .. .. .. .. .. .. .. ..
+ The 2-device layout is equivalent 2-way RAID1. The 4-device
+ layout is what a traditional RAID10 would look like. The
+ 3-device layout is what might be called a 'RAID1E - Integrated
+ Adjacent 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
diff --git a/Documentation/device-mapper/striped.txt b/Documentation/device-mapper/striped.txt
index f34d3236b9d..45f3b91ea4c 100644
--- a/Documentation/device-mapper/striped.txt
+++ b/Documentation/device-mapper/striped.txt
@@ -9,15 +9,14 @@ devices in parallel.
Parameters: <num devs> <chunk size> [<dev path> <offset>]+
<num devs>: Number of underlying devices.
- <chunk size>: Size of each chunk of data. Must be a power-of-2 and at
- least as large as the system's PAGE_SIZE.
+ <chunk size>: Size of each chunk of data. Must be at least as
+ large as the system's PAGE_SIZE.
<dev path>: Full pathname to the underlying block-device, or a
"major:minor" device-number.
<offset>: Starting sector within the device.
One or more underlying devices can be specified. The striped device size must
-be a multiple of the chunk size and a multiple of the number of underlying
+be a multiple of the chunk size multiplied by the number of underlying devices.
Example scripts
diff --git a/Documentation/device-mapper/thin-provisioning.txt b/Documentation/device-mapper/thin-provisioning.txt
index f5cfc62b7ad..30b8b83bd33 100644
--- a/Documentation/device-mapper/thin-provisioning.txt
+++ b/Documentation/device-mapper/thin-provisioning.txt
@@ -231,6 +231,9 @@ i) Constructor
no_discard_passdown: Don't pass discards down to the underlying
data device, but just remove the mapping.
+ read_only: Don't allow any changes to be made to the pool
+ metadata.
Data block size must be between 64KB (128 sectors) and 1GB
(2097152 sectors) inclusive.
@@ -239,7 +242,7 @@ ii) Status
<transaction id> <used metadata blocks>/<total metadata blocks>
<used data blocks>/<total data blocks> <held metadata root>
+ [no_]discard_passdown ro|rw
transaction id:
A 64-bit number used by userspace to help synchronise with metadata
@@ -257,6 +260,21 @@ ii) Status
held root. This feature is not yet implemented so '-' is
always returned.
+ discard_passdown|no_discard_passdown
+ Whether or not discards are actually being passed down to the
+ underlying device. When this is enabled when loading the table,
+ it can get disabled if the underlying device doesn't support it.
+ ro|rw
+ If the pool encounters certain types of device failures it will
+ drop into a read-only metadata mode in which no changes to
+ the pool metadata (like allocating new blocks) are permitted.
+ In serious cases where even a read-only mode is deemed unsafe
+ no further I/O will be permitted and the status will just
+ contain the string 'Fail'. The userspace recovery tools
+ should then be used.
iii) Messages
create_thin <dev id>
@@ -329,3 +347,7 @@ regain some space then send the 'trim' message to the pool.
ii) Status
<nr mapped sectors> <highest mapped sector>
+ If the pool has encountered device errors and failed, the status
+ will just contain the string 'Fail'. The userspace recovery
+ tools should then be used.