Root/
1 | dm-raid |
2 | ------- |
3 | |
4 | The device-mapper RAID (dm-raid) target provides a bridge from DM to MD. |
5 | It allows the MD RAID drivers to be accessed using a device-mapper |
6 | interface. |
7 | |
8 | The target is named "raid" and it accepts the following parameters: |
9 | |
10 | <raid_type> <#raid_params> <raid_params> \ |
11 | <#raid_devs> <metadata_dev0> <dev0> [.. <metadata_devN> <devN>] |
12 | |
13 | <raid_type>: |
14 | raid1 RAID1 mirroring |
15 | raid4 RAID4 dedicated parity disk |
16 | raid5_la RAID5 left asymmetric |
17 | - rotating parity 0 with data continuation |
18 | raid5_ra RAID5 right asymmetric |
19 | - rotating parity N with data continuation |
20 | raid5_ls RAID5 left symmetric |
21 | - rotating parity 0 with data restart |
22 | raid5_rs RAID5 right symmetric |
23 | - rotating parity N with data restart |
24 | raid6_zr RAID6 zero restart |
25 | - rotating parity zero (left-to-right) with data restart |
26 | raid6_nr RAID6 N restart |
27 | - rotating parity N (right-to-left) with data restart |
28 | raid6_nc RAID6 N continue |
29 | - rotating parity N (right-to-left) with data continuation |
30 | |
31 | Refererence: Chapter 4 of |
32 | http://www.snia.org/sites/default/files/SNIA_DDF_Technical_Position_v2.0.pdf |
33 | |
34 | <#raid_params>: The number of parameters that follow. |
35 | |
36 | <raid_params> consists of |
37 | Mandatory parameters: |
38 | <chunk_size>: Chunk size in sectors. This parameter is often known as |
39 | "stripe size". It is the only mandatory parameter and |
40 | is placed first. |
41 | |
42 | followed by optional parameters (in any order): |
43 | [sync|nosync] Force or prevent RAID initialization. |
44 | |
45 | [rebuild <idx>] Rebuild drive number idx (first drive is 0). |
46 | |
47 | [daemon_sleep <ms>] |
48 | Interval between runs of the bitmap daemon that |
49 | clear bits. A longer interval means less bitmap I/O but |
50 | resyncing after a failure is likely to take longer. |
51 | |
52 | [min_recovery_rate <kB/sec/disk>] Throttle RAID initialization |
53 | [max_recovery_rate <kB/sec/disk>] Throttle RAID initialization |
54 | [write_mostly <idx>] Drive index is write-mostly |
55 | [max_write_behind <sectors>] See '-write-behind=' (man mdadm) |
56 | [stripe_cache <sectors>] Stripe cache size (higher RAIDs only) |
57 | [region_size <sectors>] |
58 | The region_size multiplied by the number of regions is the |
59 | logical size of the array. The bitmap records the device |
60 | synchronisation state for each region. |
61 | |
62 | <#raid_devs>: The number of devices composing the array. |
63 | Each device consists of two entries. The first is the device |
64 | containing the metadata (if any); the second is the one containing the |
65 | data. |
66 | |
67 | If a drive has failed or is missing at creation time, a '-' can be |
68 | given for both the metadata and data drives for a given position. |
69 | |
70 | |
71 | Example tables |
72 | -------------- |
73 | # RAID4 - 4 data drives, 1 parity (no metadata devices) |
74 | # No metadata devices specified to hold superblock/bitmap info |
75 | # Chunk size of 1MiB |
76 | # (Lines separated for easy reading) |
77 | |
78 | 0 1960893648 raid \ |
79 | raid4 1 2048 \ |
80 | 5 - 8:17 - 8:33 - 8:49 - 8:65 - 8:81 |
81 | |
82 | # RAID4 - 4 data drives, 1 parity (with metadata devices) |
83 | # Chunk size of 1MiB, force RAID initialization, |
84 | # min recovery rate at 20 kiB/sec/disk |
85 | |
86 | 0 1960893648 raid \ |
87 | raid4 4 2048 sync min_recovery_rate 20 \ |
88 | 5 8:17 8:18 8:33 8:34 8:49 8:50 8:65 8:66 8:81 8:82 |
89 | |
90 | 'dmsetup table' displays the table used to construct the mapping. |
91 | The optional parameters are always printed in the order listed |
92 | above with "sync" or "nosync" always output ahead of the other |
93 | arguments, regardless of the order used when originally loading the table. |
94 | Arguments that can be repeated are ordered by value. |
95 | |
96 | 'dmsetup status' yields information on the state and health of the |
97 | array. |
98 | The output is as follows: |
99 | 1: <s> <l> raid \ |
100 | 2: <raid_type> <#devices> <1 health char for each dev> <resync_ratio> |
101 | |
102 | Line 1 is the standard output produced by device-mapper. |
103 | Line 2 is produced by the raid target, and best explained by example: |
104 | 0 1960893648 raid raid4 5 AAAAA 2/490221568 |
105 | Here we can see the RAID type is raid4, there are 5 devices - all of |
106 | which are 'A'live, and the array is 2/490221568 complete with recovery. |
107 | Faulty or missing devices are marked 'D'. Devices that are out-of-sync |
108 | are marked 'a'. |
109 |
Branches:
ben-wpan
ben-wpan-stefan
javiroman/ks7010
jz-2.6.34
jz-2.6.34-rc5
jz-2.6.34-rc6
jz-2.6.34-rc7
jz-2.6.35
jz-2.6.36
jz-2.6.37
jz-2.6.38
jz-2.6.39
jz-3.0
jz-3.1
jz-3.11
jz-3.12
jz-3.13
jz-3.15
jz-3.16
jz-3.18-dt
jz-3.2
jz-3.3
jz-3.4
jz-3.5
jz-3.6
jz-3.6-rc2-pwm
jz-3.9
jz-3.9-clk
jz-3.9-rc8
jz47xx
jz47xx-2.6.38
master
Tags:
od-2011-09-04
od-2011-09-18
v2.6.34-rc5
v2.6.34-rc6
v2.6.34-rc7
v3.9