Commit | Line | Data |
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1 | dm-raid |
2 | ------- | |
9d09e663 | 3 | |
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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. | |
9d09e663 | 7 | |
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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>: | |
b12d437b | 14 | raid1 RAID1 mirroring |
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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 | ||
40e47125 | 31 | Reference: Chapter 4 of |
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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 | |
46bed2b5 | 54 | [write_mostly <idx>] Drive index is write-mostly |
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55 | [max_write_behind <sectors>] See '-write-behind=' (man mdadm) |
56 | [stripe_cache <sectors>] Stripe cache size (higher RAIDs only) | |
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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. | |
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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 | |
b12d437b | 65 | data. |
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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 | -------------- | |
b12d437b | 73 | # RAID4 - 4 data drives, 1 parity (no metadata devices) |
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74 | # No metadata devices specified to hold superblock/bitmap info |
75 | # Chunk size of 1MiB | |
76 | # (Lines separated for easy reading) | |
c0a2fa1e | 77 | |
9d09e663 N |
78 | 0 1960893648 raid \ |
79 | raid4 1 2048 \ | |
80 | 5 - 8:17 - 8:33 - 8:49 - 8:65 - 8:81 | |
81 | ||
b12d437b | 82 | # RAID4 - 4 data drives, 1 parity (with metadata devices) |
9d09e663 N |
83 | # Chunk size of 1MiB, force RAID initialization, |
84 | # min recovery rate at 20 kiB/sec/disk | |
c0a2fa1e | 85 | |
9d09e663 | 86 | 0 1960893648 raid \ |
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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 | |
9d09e663 | 89 | |
c0a2fa1e | 90 | 'dmsetup table' displays the table used to construct the mapping. |
46bed2b5 | 91 | The optional parameters are always printed in the order listed |
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92 | above with "sync" or "nosync" always output ahead of the other |
93 | arguments, regardless of the order used when originally loading the table. | |
46bed2b5 | 94 | Arguments that can be repeated are ordered by value. |
9d09e663 | 95 | |
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96 | 'dmsetup status' yields information on the state and health of the |
97 | array. | |
98 | The output is as follows: | |
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99 | 1: <s> <l> raid \ |
100 | 2: <raid_type> <#devices> <1 health char for each dev> <resync_ratio> | |
101 | ||
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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: | |
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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. | |
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107 | Faulty or missing devices are marked 'D'. Devices that are out-of-sync |
108 | are marked 'a'. |