1 ======= 1 =======
2 dm-raid 2 dm-raid
3 ======= 3 =======
4 4
5 The device-mapper RAID (dm-raid) target provid 5 The device-mapper RAID (dm-raid) target provides a bridge from DM to MD.
6 It allows the MD RAID drivers to be accessed u 6 It allows the MD RAID drivers to be accessed using a device-mapper
7 interface. 7 interface.
8 8
9 9
10 Mapping Table Interface 10 Mapping Table Interface
11 ----------------------- 11 -----------------------
12 The target is named "raid" and it accepts the 12 The target is named "raid" and it accepts the following parameters::
13 13
14 <raid_type> <#raid_params> <raid_params> \ 14 <raid_type> <#raid_params> <raid_params> \
15 <#raid_devs> <metadata_dev0> <dev0> [.. <m 15 <#raid_devs> <metadata_dev0> <dev0> [.. <metadata_devN> <devN>]
16 16
17 <raid_type>: 17 <raid_type>:
18 18
19 ============= ============================== 19 ============= ===============================================================
20 raid0 RAID0 striping (no resilience) 20 raid0 RAID0 striping (no resilience)
21 raid1 RAID1 mirroring 21 raid1 RAID1 mirroring
22 raid4 RAID4 with dedicated last pari 22 raid4 RAID4 with dedicated last parity disk
23 raid5_n RAID5 with dedicated last pari 23 raid5_n RAID5 with dedicated last parity disk supporting takeover
24 Same as raid4 24 Same as raid4
25 25
26 - Transitory layout 26 - Transitory layout
27 raid5_la RAID5 left asymmetric 27 raid5_la RAID5 left asymmetric
28 28
29 - rotating parity 0 with data 29 - rotating parity 0 with data continuation
30 raid5_ra RAID5 right asymmetric 30 raid5_ra RAID5 right asymmetric
31 31
32 - rotating parity N with data 32 - rotating parity N with data continuation
33 raid5_ls RAID5 left symmetric 33 raid5_ls RAID5 left symmetric
34 34
35 - rotating parity 0 with data 35 - rotating parity 0 with data restart
36 raid5_rs RAID5 right symmetric 36 raid5_rs RAID5 right symmetric
37 37
38 - rotating parity N with data 38 - rotating parity N with data restart
39 raid6_zr RAID6 zero restart 39 raid6_zr RAID6 zero restart
40 40
41 - rotating parity zero (left-t 41 - rotating parity zero (left-to-right) with data restart
42 raid6_nr RAID6 N restart 42 raid6_nr RAID6 N restart
43 43
44 - rotating parity N (right-to- 44 - rotating parity N (right-to-left) with data restart
45 raid6_nc RAID6 N continue 45 raid6_nc RAID6 N continue
46 46
47 - rotating parity N (right-to- 47 - rotating parity N (right-to-left) with data continuation
48 raid6_n_6 RAID6 with dedicate parity dis 48 raid6_n_6 RAID6 with dedicate parity disks
49 49
50 - parity and Q-syndrome on the 50 - parity and Q-syndrome on the last 2 disks;
51 layout for takeover from/to 51 layout for takeover from/to raid4/raid5_n
52 raid6_la_6 Same as "raid_la" plus dedicat 52 raid6_la_6 Same as "raid_la" plus dedicated last Q-syndrome disk
53 53
54 - layout for takeover from rai 54 - layout for takeover from raid5_la from/to raid6
55 raid6_ra_6 Same as "raid5_ra" dedicated l 55 raid6_ra_6 Same as "raid5_ra" dedicated last Q-syndrome disk
56 56
57 - layout for takeover from rai 57 - layout for takeover from raid5_ra from/to raid6
58 raid6_ls_6 Same as "raid5_ls" dedicated l 58 raid6_ls_6 Same as "raid5_ls" dedicated last Q-syndrome disk
59 59
60 - layout for takeover from rai 60 - layout for takeover from raid5_ls from/to raid6
61 raid6_rs_6 Same as "raid5_rs" dedicated l 61 raid6_rs_6 Same as "raid5_rs" dedicated last Q-syndrome disk
62 62
63 - layout for takeover from rai 63 - layout for takeover from raid5_rs from/to raid6
64 raid10 Various RAID10 inspired algori 64 raid10 Various RAID10 inspired algorithms chosen by additional params
65 (see raid10_format and raid10_ 65 (see raid10_format and raid10_copies below)
66 66
67 - RAID10: Striped Mirrors (aka 67 - RAID10: Striped Mirrors (aka 'Striping on top of mirrors')
68 - RAID1E: Integrated Adjacent 68 - RAID1E: Integrated Adjacent Stripe Mirroring
69 - RAID1E: Integrated Offset St 69 - RAID1E: Integrated Offset Stripe Mirroring
70 - and other similar RAID10 var 70 - and other similar RAID10 variants
71 ============= ============================== 71 ============= ===============================================================
72 72
73 Reference: Chapter 4 of 73 Reference: Chapter 4 of
74 https://www.snia.org/sites/default/files/SNI 74 https://www.snia.org/sites/default/files/SNIA_DDF_Technical_Position_v2.0.pdf
75 75
76 <#raid_params>: The number of parameters that 76 <#raid_params>: The number of parameters that follow.
77 77
78 <raid_params> consists of 78 <raid_params> consists of
79 79
80 Mandatory parameters: 80 Mandatory parameters:
81 <chunk_size>: 81 <chunk_size>:
82 Chunk size in sectors. 82 Chunk size in sectors. This parameter is often known as
83 "stripe size". It is th 83 "stripe size". It is the only mandatory parameter and
84 is placed first. 84 is placed first.
85 85
86 followed by optional parameters (in any or 86 followed by optional parameters (in any order):
87 [sync|nosync] 87 [sync|nosync]
88 Force or prevent RAID initiali 88 Force or prevent RAID initialization.
89 89
90 [rebuild <idx>] 90 [rebuild <idx>]
91 Rebuild drive number 'idx' (fi 91 Rebuild drive number 'idx' (first drive is 0).
92 92
93 [daemon_sleep <ms>] 93 [daemon_sleep <ms>]
94 Interval between runs of the b 94 Interval between runs of the bitmap daemon that
95 clear bits. A longer interval 95 clear bits. A longer interval means less bitmap I/O but
96 resyncing after a failure is l 96 resyncing after a failure is likely to take longer.
97 97
98 [min_recovery_rate <kB/sec/disk>] 98 [min_recovery_rate <kB/sec/disk>]
99 Throttle RAID initialization 99 Throttle RAID initialization
100 [max_recovery_rate <kB/sec/disk>] 100 [max_recovery_rate <kB/sec/disk>]
101 Throttle RAID initialization 101 Throttle RAID initialization
102 [write_mostly <idx>] 102 [write_mostly <idx>]
103 Mark drive index 'idx' write-m 103 Mark drive index 'idx' write-mostly.
104 [max_write_behind <sectors>] 104 [max_write_behind <sectors>]
105 See '--write-behind=' (man mda 105 See '--write-behind=' (man mdadm)
106 [stripe_cache <sectors>] 106 [stripe_cache <sectors>]
107 Stripe cache size (RAID 4/5/6 107 Stripe cache size (RAID 4/5/6 only)
108 [region_size <sectors>] 108 [region_size <sectors>]
109 The region_size multiplied by 109 The region_size multiplied by the number of regions is the
110 logical size of the array. Th 110 logical size of the array. The bitmap records the device
111 synchronisation state for each 111 synchronisation state for each region.
112 112
113 [raid10_copies <# copies>], [raid10_ 113 [raid10_copies <# copies>], [raid10_format <near|far|offset>]
114 These two options are used to 114 These two options are used to alter the default layout of
115 a RAID10 configuration. The n 115 a RAID10 configuration. The number of copies is can be
116 specified, but the default is 116 specified, but the default is 2. There are also three
117 variations to how the copies a 117 variations to how the copies are laid down - the default
118 is "near". Near copies are wh 118 is "near". Near copies are what most people think of with
119 respect to mirroring. If thes 119 respect to mirroring. If these options are left unspecified,
120 or 'raid10_copies 2' and/or 'r 120 or 'raid10_copies 2' and/or 'raid10_format near' are given,
121 then the layouts for 2, 3 and 121 then the layouts for 2, 3 and 4 devices are:
122 122
123 ======== ========== 123 ======== ========== ==============
124 2 drives 3 drives 124 2 drives 3 drives 4 drives
125 ======== ========== 125 ======== ========== ==============
126 A1 A1 A1 A1 A2 126 A1 A1 A1 A1 A2 A1 A1 A2 A2
127 A2 A2 A2 A3 A3 127 A2 A2 A2 A3 A3 A3 A3 A4 A4
128 A3 A3 A4 A4 A5 128 A3 A3 A4 A4 A5 A5 A5 A6 A6
129 A4 A4 A5 A6 A6 129 A4 A4 A5 A6 A6 A7 A7 A8 A8
130 .. .. .. .. .. 130 .. .. .. .. .. .. .. .. ..
131 ======== ========== 131 ======== ========== ==============
132 132
133 The 2-device layout is equival 133 The 2-device layout is equivalent 2-way RAID1. The 4-device
134 layout is what a traditional R 134 layout is what a traditional RAID10 would look like. The
135 3-device layout is what might 135 3-device layout is what might be called a 'RAID1E - Integrated
136 Adjacent Stripe Mirroring'. 136 Adjacent Stripe Mirroring'.
137 137
138 If 'raid10_copies 2' and 'raid 138 If 'raid10_copies 2' and 'raid10_format far', then the layouts
139 for 2, 3 and 4 devices are: 139 for 2, 3 and 4 devices are:
140 140
141 ======== ========= 141 ======== ============ ===================
142 2 drives 3 drives 142 2 drives 3 drives 4 drives
143 ======== ========= 143 ======== ============ ===================
144 A1 A2 A1 A2 144 A1 A2 A1 A2 A3 A1 A2 A3 A4
145 A3 A4 A4 A5 145 A3 A4 A4 A5 A6 A5 A6 A7 A8
146 A5 A6 A7 A8 146 A5 A6 A7 A8 A9 A9 A10 A11 A12
147 .. .. .. .. 147 .. .. .. .. .. .. .. .. ..
148 A2 A1 A3 A1 148 A2 A1 A3 A1 A2 A2 A1 A4 A3
149 A4 A3 A6 A4 149 A4 A3 A6 A4 A5 A6 A5 A8 A7
150 A6 A5 A9 A7 150 A6 A5 A9 A7 A8 A10 A9 A12 A11
151 .. .. .. .. 151 .. .. .. .. .. .. .. .. ..
152 ======== ========= 152 ======== ============ ===================
153 153
154 If 'raid10_copies 2' and 'raid 154 If 'raid10_copies 2' and 'raid10_format offset', then the
155 layouts for 2, 3 and 4 devices 155 layouts for 2, 3 and 4 devices are:
156 156
157 ======== ========== 157 ======== ========== ================
158 2 drives 3 drives 158 2 drives 3 drives 4 drives
159 ======== ========== 159 ======== ========== ================
160 A1 A2 A1 A2 A3 160 A1 A2 A1 A2 A3 A1 A2 A3 A4
161 A2 A1 A3 A1 A2 161 A2 A1 A3 A1 A2 A2 A1 A4 A3
162 A3 A4 A4 A5 A6 162 A3 A4 A4 A5 A6 A5 A6 A7 A8
163 A4 A3 A6 A4 A5 163 A4 A3 A6 A4 A5 A6 A5 A8 A7
164 A5 A6 A7 A8 A9 164 A5 A6 A7 A8 A9 A9 A10 A11 A12
165 A6 A5 A9 A7 A8 165 A6 A5 A9 A7 A8 A10 A9 A12 A11
166 .. .. .. .. .. 166 .. .. .. .. .. .. .. .. ..
167 ======== ========== 167 ======== ========== ================
168 168
169 Here we see layouts closely ak 169 Here we see layouts closely akin to 'RAID1E - Integrated
170 Offset Stripe Mirroring'. 170 Offset Stripe Mirroring'.
171 171
172 [delta_disks <N>] 172 [delta_disks <N>]
173 The delta_disks option value ( 173 The delta_disks option value (-251 < N < +251) triggers
174 device removal (negative value 174 device removal (negative value) or device addition (positive
175 value) to any reshape supporti 175 value) to any reshape supporting raid levels 4/5/6 and 10.
176 RAID levels 4/5/6 allow for ad 176 RAID levels 4/5/6 allow for addition of devices (metadata
177 and data device tuple), raid10 177 and data device tuple), raid10_near and raid10_offset only
178 allow for device addition. rai 178 allow for device addition. raid10_far does not support any
179 reshaping at all. 179 reshaping at all.
180 A minimum of devices have to b 180 A minimum of devices have to be kept to enforce resilience,
181 which is 3 devices for raid4/5 181 which is 3 devices for raid4/5 and 4 devices for raid6.
182 182
183 [data_offset <sectors>] 183 [data_offset <sectors>]
184 This option value defines the 184 This option value defines the offset into each data device
185 where the data starts. This is 185 where the data starts. This is used to provide out-of-place
186 reshaping space to avoid writi 186 reshaping space to avoid writing over data while
187 changing the layout of stripes 187 changing the layout of stripes, hence an interruption/crash
188 may happen at any time without 188 may happen at any time without the risk of losing data.
189 E.g. when adding devices to an 189 E.g. when adding devices to an existing raid set during
190 forward reshaping, the out-of- 190 forward reshaping, the out-of-place space will be allocated
191 at the beginning of each raid 191 at the beginning of each raid device. The kernel raid4/5/6/10
192 MD personalities supporting su 192 MD personalities supporting such device addition will read the data from
193 the existing first stripes (th 193 the existing first stripes (those with smaller number of stripes)
194 starting at data_offset to fil 194 starting at data_offset to fill up a new stripe with the larger
195 number of stripes, calculate t 195 number of stripes, calculate the redundancy blocks (CRC/Q-syndrome)
196 and write that new stripe to o 196 and write that new stripe to offset 0. Same will be applied to all
197 N-1 other new stripes. This ou 197 N-1 other new stripes. This out-of-place scheme is used to change
198 the RAID type (i.e. the alloca 198 the RAID type (i.e. the allocation algorithm) as well, e.g.
199 changing from raid5_ls to raid 199 changing from raid5_ls to raid5_n.
200 200
201 [journal_dev <dev>] 201 [journal_dev <dev>]
202 This option adds a journal dev 202 This option adds a journal device to raid4/5/6 raid sets and
203 uses it to close the 'write ho 203 uses it to close the 'write hole' caused by the non-atomic updates
204 to the component devices which 204 to the component devices which can cause data loss during recovery.
205 The journal device is used as 205 The journal device is used as writethrough thus causing writes to
206 be throttled versus non-journa 206 be throttled versus non-journaled raid4/5/6 sets.
207 Takeover/reshape is not possib 207 Takeover/reshape is not possible with a raid4/5/6 journal device;
208 it has to be deconfigured befo 208 it has to be deconfigured before requesting these.
209 209
210 [journal_mode <mode>] 210 [journal_mode <mode>]
211 This option sets the caching m 211 This option sets the caching mode on journaled raid4/5/6 raid sets
212 (see 'journal_dev <dev>' above 212 (see 'journal_dev <dev>' above) to 'writethrough' or 'writeback'.
213 If 'writeback' is selected the 213 If 'writeback' is selected the journal device has to be resilient
214 and must not suffer from the ' 214 and must not suffer from the 'write hole' problem itself (e.g. use
215 raid1 or raid10) to avoid a si 215 raid1 or raid10) to avoid a single point of failure.
216 216
217 <#raid_devs>: The number of devices composing 217 <#raid_devs>: The number of devices composing the array.
218 Each device consists of two entries. 218 Each device consists of two entries. The first is the device
219 containing the metadata (if any); the 219 containing the metadata (if any); the second is the one containing the
220 data. A Maximum of 64 metadata/data de 220 data. A Maximum of 64 metadata/data device entries are supported
221 up to target version 1.8.0. 221 up to target version 1.8.0.
222 1.9.0 supports up to 253 which is enfo 222 1.9.0 supports up to 253 which is enforced by the used MD kernel runtime.
223 223
224 If a drive has failed or is missing at 224 If a drive has failed or is missing at creation time, a '-' can be
225 given for both the metadata and data d 225 given for both the metadata and data drives for a given position.
226 226
227 227
228 Example Tables 228 Example Tables
229 -------------- 229 --------------
230 230
231 :: 231 ::
232 232
233 # RAID4 - 4 data drives, 1 parity (no metada 233 # RAID4 - 4 data drives, 1 parity (no metadata devices)
234 # No metadata devices specified to hold supe 234 # No metadata devices specified to hold superblock/bitmap info
235 # Chunk size of 1MiB 235 # Chunk size of 1MiB
236 # (Lines separated for easy reading) 236 # (Lines separated for easy reading)
237 237
238 0 1960893648 raid \ 238 0 1960893648 raid \
239 raid4 1 2048 \ 239 raid4 1 2048 \
240 5 - 8:17 - 8:33 - 8:49 - 8:65 - 8:81 240 5 - 8:17 - 8:33 - 8:49 - 8:65 - 8:81
241 241
242 # RAID4 - 4 data drives, 1 parity (with meta 242 # RAID4 - 4 data drives, 1 parity (with metadata devices)
243 # Chunk size of 1MiB, force RAID initializat 243 # Chunk size of 1MiB, force RAID initialization,
244 # min recovery rate at 20 kiB/sec/disk 244 # min recovery rate at 20 kiB/sec/disk
245 245
246 0 1960893648 raid \ 246 0 1960893648 raid \
247 raid4 4 2048 sync min_recovery_rate 247 raid4 4 2048 sync min_recovery_rate 20 \
248 5 8:17 8:18 8:33 8:34 8:49 8:50 8:65 248 5 8:17 8:18 8:33 8:34 8:49 8:50 8:65 8:66 8:81 8:82
249 249
250 250
251 Status Output 251 Status Output
252 ------------- 252 -------------
253 'dmsetup table' displays the table used to con 253 'dmsetup table' displays the table used to construct the mapping.
254 The optional parameters are always printed in 254 The optional parameters are always printed in the order listed
255 above with "sync" or "nosync" always output ah 255 above with "sync" or "nosync" always output ahead of the other
256 arguments, regardless of the order used when o 256 arguments, regardless of the order used when originally loading the table.
257 Arguments that can be repeated are ordered by 257 Arguments that can be repeated are ordered by value.
258 258
259 259
260 'dmsetup status' yields information on the sta 260 'dmsetup status' yields information on the state and health of the array.
261 The output is as follows (normally a single li 261 The output is as follows (normally a single line, but expanded here for
262 clarity):: 262 clarity)::
263 263
264 1: <s> <l> raid \ 264 1: <s> <l> raid \
265 2: <raid_type> <#devices> <health_chars 265 2: <raid_type> <#devices> <health_chars> \
266 3: <sync_ratio> <sync_action> <mismatch 266 3: <sync_ratio> <sync_action> <mismatch_cnt>
267 267
268 Line 1 is the standard output produced by devi 268 Line 1 is the standard output produced by device-mapper.
269 269
270 Line 2 & 3 are produced by the raid target and 270 Line 2 & 3 are produced by the raid target and are best explained by example::
271 271
272 0 1960893648 raid raid4 5 AAAAA 2/4902 272 0 1960893648 raid raid4 5 AAAAA 2/490221568 init 0
273 273
274 Here we can see the RAID type is raid4, there 274 Here we can see the RAID type is raid4, there are 5 devices - all of
275 which are 'A'live, and the array is 2/49022156 275 which are 'A'live, and the array is 2/490221568 complete with its initial
276 recovery. Here is a fuller description of the 276 recovery. Here is a fuller description of the individual fields:
277 277
278 =============== ====================== 278 =============== =========================================================
279 <raid_type> Same as the <raid_type 279 <raid_type> Same as the <raid_type> used to create the array.
280 <health_chars> One char for each devi 280 <health_chars> One char for each device, indicating:
281 281
282 - 'A' = alive and in-s 282 - 'A' = alive and in-sync
283 - 'a' = alive but not 283 - 'a' = alive but not in-sync
284 - 'D' = dead/failed. 284 - 'D' = dead/failed.
285 <sync_ratio> The ratio indicating h 285 <sync_ratio> The ratio indicating how much of the array has undergone
286 the process described 286 the process described by 'sync_action'. If the
287 'sync_action' is "chec 287 'sync_action' is "check" or "repair", then the process
288 of "resync" or "recove 288 of "resync" or "recover" can be considered complete.
289 <sync_action> One of the following p 289 <sync_action> One of the following possible states:
290 290
291 idle 291 idle
292 - No synchroni 292 - No synchronization action is being performed.
293 frozen 293 frozen
294 - The current 294 - The current action has been halted.
295 resync 295 resync
296 - Array is und 296 - Array is undergoing its initial synchronization
297 or is resync 297 or is resynchronizing after an unclean shutdown
298 (possibly ai 298 (possibly aided by a bitmap).
299 recover 299 recover
300 - A device in 300 - A device in the array is being rebuilt or
301 replaced. 301 replaced.
302 check 302 check
303 - A user-initi 303 - A user-initiated full check of the array is
304 being perfor 304 being performed. All blocks are read and
305 checked for 305 checked for consistency. The number of
306 discrepancie 306 discrepancies found are recorded in
307 <mismatch_cn 307 <mismatch_cnt>. No changes are made to the
308 array by thi 308 array by this action.
309 repair 309 repair
310 - The same as 310 - The same as "check", but discrepancies are
311 corrected. 311 corrected.
312 reshape 312 reshape
313 - The array is 313 - The array is undergoing a reshape.
314 <mismatch_cnt> The number of discrepa 314 <mismatch_cnt> The number of discrepancies found between mirror copies
315 in RAID1/10 or wrong p 315 in RAID1/10 or wrong parity values found in RAID4/5/6.
316 This value is valid on 316 This value is valid only after a "check" of the array
317 is performed. A healt 317 is performed. A healthy array has a 'mismatch_cnt' of 0.
318 <data_offset> The current data offse 318 <data_offset> The current data offset to the start of the user data on
319 each component device 319 each component device of a raid set (see the respective
320 raid parameter to supp 320 raid parameter to support out-of-place reshaping).
321 <journal_char> - 'A' - active write-t 321 <journal_char> - 'A' - active write-through journal device.
322 - 'a' - active write-b 322 - 'a' - active write-back journal device.
323 - 'D' - dead journal d 323 - 'D' - dead journal device.
324 - '-' - no journal dev 324 - '-' - no journal device.
325 =============== ====================== 325 =============== =========================================================
326 326
327 327
328 Message Interface 328 Message Interface
329 ----------------- 329 -----------------
330 The dm-raid target will accept certain actions 330 The dm-raid target will accept certain actions through the 'message' interface.
331 ('man dmsetup' for more information on the mes 331 ('man dmsetup' for more information on the message interface.) These actions
332 include: 332 include:
333 333
334 ========= ============================ 334 ========= ================================================
335 "idle" Halt the current sync action 335 "idle" Halt the current sync action.
336 "frozen" Freeze the current sync acti 336 "frozen" Freeze the current sync action.
337 "resync" Initiate/continue a resync. 337 "resync" Initiate/continue a resync.
338 "recover" Initiate/continue a recover 338 "recover" Initiate/continue a recover process.
339 "check" Initiate a check (i.e. a "sc 339 "check" Initiate a check (i.e. a "scrub") of the array.
340 "repair" Initiate a repair of the arr 340 "repair" Initiate a repair of the array.
341 ========= ============================ 341 ========= ================================================
342 342
343 343
344 Discard Support 344 Discard Support
345 --------------- 345 ---------------
346 The implementation of discard support among ha 346 The implementation of discard support among hardware vendors varies.
347 When a block is discarded, some storage device 347 When a block is discarded, some storage devices will return zeroes when
348 the block is read. These devices set the 'dis 348 the block is read. These devices set the 'discard_zeroes_data'
349 attribute. Other devices will return random d 349 attribute. Other devices will return random data. Confusingly, some
350 devices that advertise 'discard_zeroes_data' w 350 devices that advertise 'discard_zeroes_data' will not reliably return
351 zeroes when discarded blocks are read! Since 351 zeroes when discarded blocks are read! Since RAID 4/5/6 uses blocks
352 from a number of devices to calculate parity b 352 from a number of devices to calculate parity blocks and (for performance
353 reasons) relies on 'discard_zeroes_data' being 353 reasons) relies on 'discard_zeroes_data' being reliable, it is important
354 that the devices be consistent. Blocks may be 354 that the devices be consistent. Blocks may be discarded in the middle
355 of a RAID 4/5/6 stripe and if subsequent read 355 of a RAID 4/5/6 stripe and if subsequent read results are not
356 consistent, the parity blocks may be calculate 356 consistent, the parity blocks may be calculated differently at any time;
357 making the parity blocks useless for redundanc 357 making the parity blocks useless for redundancy. It is important to
358 understand how your hardware behaves with disc 358 understand how your hardware behaves with discards if you are going to
359 enable discards with RAID 4/5/6. 359 enable discards with RAID 4/5/6.
360 360
361 Since the behavior of storage devices is unrel 361 Since the behavior of storage devices is unreliable in this respect,
362 even when reporting 'discard_zeroes_data', by 362 even when reporting 'discard_zeroes_data', by default RAID 4/5/6
363 discard support is disabled -- this ensures da 363 discard support is disabled -- this ensures data integrity at the
364 expense of losing some performance. 364 expense of losing some performance.
365 365
366 Storage devices that properly support 'discard 366 Storage devices that properly support 'discard_zeroes_data' are
367 increasingly whitelisted in the kernel and can 367 increasingly whitelisted in the kernel and can thus be trusted.
368 368
369 For trusted devices, the following dm-raid mod 369 For trusted devices, the following dm-raid module parameter can be set
370 to safely enable discard support for RAID 4/5/ 370 to safely enable discard support for RAID 4/5/6:
371 371
372 'devices_handle_discards_safely' 372 'devices_handle_discards_safely'
373 373
374 374
375 Version History 375 Version History
376 --------------- 376 ---------------
377 377
378 :: 378 ::
379 379
380 1.0.0 Initial version. Support for RAID 4/5 380 1.0.0 Initial version. Support for RAID 4/5/6
381 1.1.0 Added support for RAID 1 381 1.1.0 Added support for RAID 1
382 1.2.0 Handle creation of arrays that contain 382 1.2.0 Handle creation of arrays that contain failed devices.
383 1.3.0 Added support for RAID 10 383 1.3.0 Added support for RAID 10
384 1.3.1 Allow device replacement/rebuild for R 384 1.3.1 Allow device replacement/rebuild for RAID 10
385 1.3.2 Fix/improve redundancy checking for RA 385 1.3.2 Fix/improve redundancy checking for RAID10
386 1.4.0 Non-functional change. Removes arg fr 386 1.4.0 Non-functional change. Removes arg from mapping function.
387 1.4.1 RAID10 fix redundancy validation check 387 1.4.1 RAID10 fix redundancy validation checks (commit 55ebbb5).
388 1.4.2 Add RAID10 "far" and "offset" algorith 388 1.4.2 Add RAID10 "far" and "offset" algorithm support.
389 1.5.0 Add message interface to allow manipul 389 1.5.0 Add message interface to allow manipulation of the sync_action.
390 New status (STATUSTYPE_INFO) fields: s 390 New status (STATUSTYPE_INFO) fields: sync_action and mismatch_cnt.
391 1.5.1 Add ability to restore transiently fai 391 1.5.1 Add ability to restore transiently failed devices on resume.
392 1.5.2 'mismatch_cnt' is zero unless [last_]s 392 1.5.2 'mismatch_cnt' is zero unless [last_]sync_action is "check".
393 1.6.0 Add discard support (and devices_handl 393 1.6.0 Add discard support (and devices_handle_discard_safely module param).
394 1.7.0 Add support for MD RAID0 mappings. 394 1.7.0 Add support for MD RAID0 mappings.
395 1.8.0 Explicitly check for compatible flags 395 1.8.0 Explicitly check for compatible flags in the superblock metadata
396 and reject to start the raid set if an 396 and reject to start the raid set if any are set by a newer
397 target version, thus avoiding data cor 397 target version, thus avoiding data corruption on a raid set
398 with a reshape in progress. 398 with a reshape in progress.
399 1.9.0 Add support for RAID level takeover/re 399 1.9.0 Add support for RAID level takeover/reshape/region size
400 and set size reduction. 400 and set size reduction.
401 1.9.1 Fix activation of existing RAID 4/10 m 401 1.9.1 Fix activation of existing RAID 4/10 mapped devices
402 1.9.2 Don't emit '- -' on the status table l 402 1.9.2 Don't emit '- -' on the status table line in case the constructor
403 fails reading a superblock. Correctly 403 fails reading a superblock. Correctly emit 'maj:min1 maj:min2' and
404 'D' on the status line. If '- -' is p 404 'D' on the status line. If '- -' is passed into the constructor, emit
405 '- -' on the table line and '-' as the 405 '- -' on the table line and '-' as the status line health character.
406 1.10.0 Add support for raid4/5/6 journal devi 406 1.10.0 Add support for raid4/5/6 journal device
407 1.10.1 Fix data corruption on reshape request 407 1.10.1 Fix data corruption on reshape request
408 1.11.0 Fix table line argument order 408 1.11.0 Fix table line argument order
409 (wrong raid10_copies/raid10_format seq 409 (wrong raid10_copies/raid10_format sequence)
410 1.11.1 Add raid4/5/6 journal write-back suppo 410 1.11.1 Add raid4/5/6 journal write-back support via journal_mode option
411 1.12.1 Fix for MD deadlock between mddev_susp 411 1.12.1 Fix for MD deadlock between mddev_suspend() and md_write_start() available
412 1.13.0 Fix dev_health status at end of "recov 412 1.13.0 Fix dev_health status at end of "recover" (was 'a', now 'A')
413 1.13.1 Fix deadlock caused by early md_stop_w 413 1.13.1 Fix deadlock caused by early md_stop_writes(). Also fix size an
414 state races. 414 state races.
415 1.13.2 Fix raid redundancy validation and avo 415 1.13.2 Fix raid redundancy validation and avoid keeping raid set frozen
416 1.14.0 Fix reshape race on small devices. Fi 416 1.14.0 Fix reshape race on small devices. Fix stripe adding reshape
417 deadlock/potential data corruption. U 417 deadlock/potential data corruption. Update superblock when
418 specific devices are requested via reb 418 specific devices are requested via rebuild. Fix RAID leg
419 rebuild errors. 419 rebuild errors.
420 1.15.0 Fix size extensions not being synchron 420 1.15.0 Fix size extensions not being synchronized in case of new MD bitmap
421 pages allocated; also fix those not o 421 pages allocated; also fix those not occurring after previous reductions
422 1.15.1 Fix argument count and arguments for r 422 1.15.1 Fix argument count and arguments for rebuild/write_mostly/journal_(dev|mode)
423 on the status line. 423 on the status line.
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