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1#
2# Block device driver configuration
3#
4
5menuconfig MD
6 bool "Multiple devices driver support (RAID and LVM)"
7 depends on BLOCK
8 help
9 Support multiple physical spindles through a single logical device.
10 Required for RAID and logical volume management.
11
12if MD
13
14config BLK_DEV_MD
15 tristate "RAID support"
16 ---help---
17 This driver lets you combine several hard disk partitions into one
18 logical block device. This can be used to simply append one
19 partition to another one or to combine several redundant hard disks
20 into a RAID1/4/5 device so as to provide protection against hard
21 disk failures. This is called "Software RAID" since the combining of
22 the partitions is done by the kernel. "Hardware RAID" means that the
23 combining is done by a dedicated controller; if you have such a
24 controller, you do not need to say Y here.
25
26 More information about Software RAID on Linux is contained in the
27 Software RAID mini-HOWTO, available from
28 <http://www.tldp.org/docs.html#howto>. There you will also learn
29 where to get the supporting user space utilities raidtools.
30
31 If unsure, say N.
32
33config MD_AUTODETECT
34 bool "Autodetect RAID arrays during kernel boot"
35 depends on BLK_DEV_MD=y
36 default y
37 ---help---
38 If you say Y here, then the kernel will try to autodetect raid
39 arrays as part of its boot process.
40
41 If you don't use raid and say Y, this autodetection can cause
42 a several-second delay in the boot time due to various
43 synchronisation steps that are part of this step.
44
45 If unsure, say Y.
46
47config MD_LINEAR
48 tristate "Linear (append) mode"
49 depends on BLK_DEV_MD
50 ---help---
51 If you say Y here, then your multiple devices driver will be able to
52 use the so-called linear mode, i.e. it will combine the hard disk
53 partitions by simply appending one to the other.
54
55 To compile this as a module, choose M here: the module
56 will be called linear.
57
58 If unsure, say Y.
59
60config MD_RAID0
61 tristate "RAID-0 (striping) mode"
62 depends on BLK_DEV_MD
63 ---help---
64 If you say Y here, then your multiple devices driver will be able to
65 use the so-called raid0 mode, i.e. it will combine the hard disk
66 partitions into one logical device in such a fashion as to fill them
67 up evenly, one chunk here and one chunk there. This will increase
68 the throughput rate if the partitions reside on distinct disks.
69
70 Information about Software RAID on Linux is contained in the
71 Software-RAID mini-HOWTO, available from
72 <http://www.tldp.org/docs.html#howto>. There you will also
73 learn where to get the supporting user space utilities raidtools.
74
75 To compile this as a module, choose M here: the module
76 will be called raid0.
77
78 If unsure, say Y.
79
80config MD_RAID1
81 tristate "RAID-1 (mirroring) mode"
82 depends on BLK_DEV_MD
83 ---help---
84 A RAID-1 set consists of several disk drives which are exact copies
85 of each other. In the event of a mirror failure, the RAID driver
86 will continue to use the operational mirrors in the set, providing
87 an error free MD (multiple device) to the higher levels of the
88 kernel. In a set with N drives, the available space is the capacity
89 of a single drive, and the set protects against a failure of (N - 1)
90 drives.
91
92 Information about Software RAID on Linux is contained in the
93 Software-RAID mini-HOWTO, available from
94 <http://www.tldp.org/docs.html#howto>. There you will also
95 learn where to get the supporting user space utilities raidtools.
96
97 If you want to use such a RAID-1 set, say Y. To compile this code
98 as a module, choose M here: the module will be called raid1.
99
100 If unsure, say Y.
101
102config MD_RAID10
103 tristate "RAID-10 (mirrored striping) mode"
104 depends on BLK_DEV_MD
105 ---help---
106 RAID-10 provides a combination of striping (RAID-0) and
107 mirroring (RAID-1) with easier configuration and more flexible
108 layout.
109 Unlike RAID-0, but like RAID-1, RAID-10 requires all devices to
110 be the same size (or at least, only as much as the smallest device
111 will be used).
112 RAID-10 provides a variety of layouts that provide different levels
113 of redundancy and performance.
114
115 RAID-10 requires mdadm-1.7.0 or later, available at:
116
117 ftp://ftp.kernel.org/pub/linux/utils/raid/mdadm/
118
119 If unsure, say Y.
120
121config MD_RAID456
122 tristate "RAID-4/RAID-5/RAID-6 mode"
123 depends on BLK_DEV_MD
124 select RAID6_PQ
125 select ASYNC_MEMCPY
126 select ASYNC_XOR
127 select ASYNC_PQ
128 select ASYNC_RAID6_RECOV
129 ---help---
130 A RAID-5 set of N drives with a capacity of C MB per drive provides
131 the capacity of C * (N - 1) MB, and protects against a failure
132 of a single drive. For a given sector (row) number, (N - 1) drives
133 contain data sectors, and one drive contains the parity protection.
134 For a RAID-4 set, the parity blocks are present on a single drive,
135 while a RAID-5 set distributes the parity across the drives in one
136 of the available parity distribution methods.
137
138 A RAID-6 set of N drives with a capacity of C MB per drive
139 provides the capacity of C * (N - 2) MB, and protects
140 against a failure of any two drives. For a given sector
141 (row) number, (N - 2) drives contain data sectors, and two
142 drives contains two independent redundancy syndromes. Like
143 RAID-5, RAID-6 distributes the syndromes across the drives
144 in one of the available parity distribution methods.
145
146 Information about Software RAID on Linux is contained in the
147 Software-RAID mini-HOWTO, available from
148 <http://www.tldp.org/docs.html#howto>. There you will also
149 learn where to get the supporting user space utilities raidtools.
150
151 If you want to use such a RAID-4/RAID-5/RAID-6 set, say Y. To
152 compile this code as a module, choose M here: the module
153 will be called raid456.
154
155 If unsure, say Y.
156
157config MULTICORE_RAID456
158 bool "RAID-4/RAID-5/RAID-6 Multicore processing (EXPERIMENTAL)"
159 depends on MD_RAID456
160 depends on SMP
161 depends on EXPERIMENTAL
162 ---help---
163 Enable the raid456 module to dispatch per-stripe raid operations to a
164 thread pool.
165
166 If unsure, say N.
167
168config MD_MULTIPATH
169 tristate "Multipath I/O support"
170 depends on BLK_DEV_MD
171 help
172 MD_MULTIPATH provides a simple multi-path personality for use
173 the MD framework. It is not under active development. New
174 projects should consider using DM_MULTIPATH which has more
175 features and more testing.
176
177 If unsure, say N.
178
179config MD_FAULTY
180 tristate "Faulty test module for MD"
181 depends on BLK_DEV_MD
182 help
183 The "faulty" module allows for a block device that occasionally returns
184 read or write errors. It is useful for testing.
185
186 In unsure, say N.
187
188config BLK_DEV_DM
189 tristate "Device mapper support"
190 ---help---
191 Device-mapper is a low level volume manager. It works by allowing
192 people to specify mappings for ranges of logical sectors. Various
193 mapping types are available, in addition people may write their own
194 modules containing custom mappings if they wish.
195
196 Higher level volume managers such as LVM2 use this driver.
197
198 To compile this as a module, choose M here: the module will be
199 called dm-mod.
200
201 If unsure, say N.
202
203config DM_DEBUG
204 boolean "Device mapper debugging support"
205 depends on BLK_DEV_DM
206 ---help---
207 Enable this for messages that may help debug device-mapper problems.
208
209 If unsure, say N.
210
211config DM_BUFIO
212 tristate
213 depends on BLK_DEV_DM && EXPERIMENTAL
214 ---help---
215 This interface allows you to do buffered I/O on a device and acts
216 as a cache, holding recently-read blocks in memory and performing
217 delayed writes.
218
219source "drivers/md/persistent-data/Kconfig"
220
221config DM_CRYPT
222 tristate "Crypt target support"
223 depends on BLK_DEV_DM
224 select CRYPTO
225 select CRYPTO_CBC
226 ---help---
227 This device-mapper target allows you to create a device that
228 transparently encrypts the data on it. You'll need to activate
229 the ciphers you're going to use in the cryptoapi configuration.
230
231 Information on how to use dm-crypt can be found on
232
233 <http://www.saout.de/misc/dm-crypt/>
234
235 To compile this code as a module, choose M here: the module will
236 be called dm-crypt.
237
238 If unsure, say N.
239
240config DM_SNAPSHOT
241 tristate "Snapshot target"
242 depends on BLK_DEV_DM
243 ---help---
244 Allow volume managers to take writable snapshots of a device.
245
246config DM_THIN_PROVISIONING
247 tristate "Thin provisioning target (EXPERIMENTAL)"
248 depends on BLK_DEV_DM && EXPERIMENTAL
249 select DM_PERSISTENT_DATA
250 ---help---
251 Provides thin provisioning and snapshots that share a data store.
252
253config DM_DEBUG_BLOCK_STACK_TRACING
254 boolean "Keep stack trace of thin provisioning block lock holders"
255 depends on STACKTRACE_SUPPORT && DM_THIN_PROVISIONING
256 select STACKTRACE
257 ---help---
258 Enable this for messages that may help debug problems with the
259 block manager locking used by thin provisioning.
260
261 If unsure, say N.
262
263config DM_DEBUG_SPACE_MAPS
264 boolean "Extra validation for thin provisioning space maps"
265 depends on DM_THIN_PROVISIONING
266 ---help---
267 Enable this for messages that may help debug problems with the
268 space maps used by thin provisioning.
269
270 If unsure, say N.
271
272config DM_MIRROR
273 tristate "Mirror target"
274 depends on BLK_DEV_DM
275 ---help---
276 Allow volume managers to mirror logical volumes, also
277 needed for live data migration tools such as 'pvmove'.
278
279config DM_RAID
280 tristate "RAID 1/4/5/6 target"
281 depends on BLK_DEV_DM
282 select MD_RAID1
283 select MD_RAID456
284 select BLK_DEV_MD
285 ---help---
286 A dm target that supports RAID1, RAID4, RAID5 and RAID6 mappings
287
288 A RAID-5 set of N drives with a capacity of C MB per drive provides
289 the capacity of C * (N - 1) MB, and protects against a failure
290 of a single drive. For a given sector (row) number, (N - 1) drives
291 contain data sectors, and one drive contains the parity protection.
292 For a RAID-4 set, the parity blocks are present on a single drive,
293 while a RAID-5 set distributes the parity across the drives in one
294 of the available parity distribution methods.
295
296 A RAID-6 set of N drives with a capacity of C MB per drive
297 provides the capacity of C * (N - 2) MB, and protects
298 against a failure of any two drives. For a given sector
299 (row) number, (N - 2) drives contain data sectors, and two
300 drives contains two independent redundancy syndromes. Like
301 RAID-5, RAID-6 distributes the syndromes across the drives
302 in one of the available parity distribution methods.
303
304config DM_LOG_USERSPACE
305 tristate "Mirror userspace logging (EXPERIMENTAL)"
306 depends on DM_MIRROR && EXPERIMENTAL && NET
307 select CONNECTOR
308 ---help---
309 The userspace logging module provides a mechanism for
310 relaying the dm-dirty-log API to userspace. Log designs
311 which are more suited to userspace implementation (e.g.
312 shared storage logs) or experimental logs can be implemented
313 by leveraging this framework.
314
315config DM_ZERO
316 tristate "Zero target"
317 depends on BLK_DEV_DM
318 ---help---
319 A target that discards writes, and returns all zeroes for
320 reads. Useful in some recovery situations.
321
322config DM_MULTIPATH
323 tristate "Multipath target"
324 depends on BLK_DEV_DM
325 # nasty syntax but means make DM_MULTIPATH independent
326 # of SCSI_DH if the latter isn't defined but if
327 # it is, DM_MULTIPATH must depend on it. We get a build
328 # error if SCSI_DH=m and DM_MULTIPATH=y
329 depends on SCSI_DH || !SCSI_DH
330 ---help---
331 Allow volume managers to support multipath hardware.
332
333config DM_MULTIPATH_QL
334 tristate "I/O Path Selector based on the number of in-flight I/Os"
335 depends on DM_MULTIPATH
336 ---help---
337 This path selector is a dynamic load balancer which selects
338 the path with the least number of in-flight I/Os.
339
340 If unsure, say N.
341
342config DM_MULTIPATH_ST
343 tristate "I/O Path Selector based on the service time"
344 depends on DM_MULTIPATH
345 ---help---
346 This path selector is a dynamic load balancer which selects
347 the path expected to complete the incoming I/O in the shortest
348 time.
349
350 If unsure, say N.
351
352config DM_DELAY
353 tristate "I/O delaying target (EXPERIMENTAL)"
354 depends on BLK_DEV_DM && EXPERIMENTAL
355 ---help---
356 A target that delays reads and/or writes and can send
357 them to different devices. Useful for testing.
358
359 If unsure, say N.
360
361config DM_UEVENT
362 bool "DM uevents"
363 depends on BLK_DEV_DM
364 ---help---
365 Generate udev events for DM events.
366
367config DM_FLAKEY
368 tristate "Flakey target (EXPERIMENTAL)"
369 depends on BLK_DEV_DM && EXPERIMENTAL
370 ---help---
371 A target that intermittently fails I/O for debugging purposes.
372
373config DM_VERITY
374 tristate "Verity target support (EXPERIMENTAL)"
375 depends on BLK_DEV_DM && EXPERIMENTAL
376 select CRYPTO
377 select CRYPTO_HASH
378 select DM_BUFIO
379 ---help---
380 This device-mapper target creates a read-only device that
381 transparently validates the data on one underlying device against
382 a pre-generated tree of cryptographic checksums stored on a second
383 device.
384
385 You'll need to activate the digests you're going to use in the
386 cryptoapi configuration.
387
388 To compile this code as a module, choose M here: the module will
389 be called dm-verity.
390
391 If unsure, say N.
392
393endif # MD
1#
2# Block device driver configuration
3#
4
5menuconfig MD
6 bool "Multiple devices driver support (RAID and LVM)"
7 depends on BLOCK
8 help
9 Support multiple physical spindles through a single logical device.
10 Required for RAID and logical volume management.
11
12if MD
13
14config BLK_DEV_MD
15 tristate "RAID support"
16 ---help---
17 This driver lets you combine several hard disk partitions into one
18 logical block device. This can be used to simply append one
19 partition to another one or to combine several redundant hard disks
20 into a RAID1/4/5 device so as to provide protection against hard
21 disk failures. This is called "Software RAID" since the combining of
22 the partitions is done by the kernel. "Hardware RAID" means that the
23 combining is done by a dedicated controller; if you have such a
24 controller, you do not need to say Y here.
25
26 More information about Software RAID on Linux is contained in the
27 Software RAID mini-HOWTO, available from
28 <http://www.tldp.org/docs.html#howto>. There you will also learn
29 where to get the supporting user space utilities raidtools.
30
31 If unsure, say N.
32
33config MD_AUTODETECT
34 bool "Autodetect RAID arrays during kernel boot"
35 depends on BLK_DEV_MD=y
36 default y
37 ---help---
38 If you say Y here, then the kernel will try to autodetect raid
39 arrays as part of its boot process.
40
41 If you don't use raid and say Y, this autodetection can cause
42 a several-second delay in the boot time due to various
43 synchronisation steps that are part of this step.
44
45 If unsure, say Y.
46
47config MD_LINEAR
48 tristate "Linear (append) mode"
49 depends on BLK_DEV_MD
50 ---help---
51 If you say Y here, then your multiple devices driver will be able to
52 use the so-called linear mode, i.e. it will combine the hard disk
53 partitions by simply appending one to the other.
54
55 To compile this as a module, choose M here: the module
56 will be called linear.
57
58 If unsure, say Y.
59
60config MD_RAID0
61 tristate "RAID-0 (striping) mode"
62 depends on BLK_DEV_MD
63 ---help---
64 If you say Y here, then your multiple devices driver will be able to
65 use the so-called raid0 mode, i.e. it will combine the hard disk
66 partitions into one logical device in such a fashion as to fill them
67 up evenly, one chunk here and one chunk there. This will increase
68 the throughput rate if the partitions reside on distinct disks.
69
70 Information about Software RAID on Linux is contained in the
71 Software-RAID mini-HOWTO, available from
72 <http://www.tldp.org/docs.html#howto>. There you will also
73 learn where to get the supporting user space utilities raidtools.
74
75 To compile this as a module, choose M here: the module
76 will be called raid0.
77
78 If unsure, say Y.
79
80config MD_RAID1
81 tristate "RAID-1 (mirroring) mode"
82 depends on BLK_DEV_MD
83 ---help---
84 A RAID-1 set consists of several disk drives which are exact copies
85 of each other. In the event of a mirror failure, the RAID driver
86 will continue to use the operational mirrors in the set, providing
87 an error free MD (multiple device) to the higher levels of the
88 kernel. In a set with N drives, the available space is the capacity
89 of a single drive, and the set protects against a failure of (N - 1)
90 drives.
91
92 Information about Software RAID on Linux is contained in the
93 Software-RAID mini-HOWTO, available from
94 <http://www.tldp.org/docs.html#howto>. There you will also
95 learn where to get the supporting user space utilities raidtools.
96
97 If you want to use such a RAID-1 set, say Y. To compile this code
98 as a module, choose M here: the module will be called raid1.
99
100 If unsure, say Y.
101
102config MD_RAID10
103 tristate "RAID-10 (mirrored striping) mode"
104 depends on BLK_DEV_MD
105 ---help---
106 RAID-10 provides a combination of striping (RAID-0) and
107 mirroring (RAID-1) with easier configuration and more flexible
108 layout.
109 Unlike RAID-0, but like RAID-1, RAID-10 requires all devices to
110 be the same size (or at least, only as much as the smallest device
111 will be used).
112 RAID-10 provides a variety of layouts that provide different levels
113 of redundancy and performance.
114
115 RAID-10 requires mdadm-1.7.0 or later, available at:
116
117 ftp://ftp.kernel.org/pub/linux/utils/raid/mdadm/
118
119 If unsure, say Y.
120
121config MD_RAID456
122 tristate "RAID-4/RAID-5/RAID-6 mode"
123 depends on BLK_DEV_MD
124 select RAID6_PQ
125 select ASYNC_MEMCPY
126 select ASYNC_XOR
127 select ASYNC_PQ
128 select ASYNC_RAID6_RECOV
129 ---help---
130 A RAID-5 set of N drives with a capacity of C MB per drive provides
131 the capacity of C * (N - 1) MB, and protects against a failure
132 of a single drive. For a given sector (row) number, (N - 1) drives
133 contain data sectors, and one drive contains the parity protection.
134 For a RAID-4 set, the parity blocks are present on a single drive,
135 while a RAID-5 set distributes the parity across the drives in one
136 of the available parity distribution methods.
137
138 A RAID-6 set of N drives with a capacity of C MB per drive
139 provides the capacity of C * (N - 2) MB, and protects
140 against a failure of any two drives. For a given sector
141 (row) number, (N - 2) drives contain data sectors, and two
142 drives contains two independent redundancy syndromes. Like
143 RAID-5, RAID-6 distributes the syndromes across the drives
144 in one of the available parity distribution methods.
145
146 Information about Software RAID on Linux is contained in the
147 Software-RAID mini-HOWTO, available from
148 <http://www.tldp.org/docs.html#howto>. There you will also
149 learn where to get the supporting user space utilities raidtools.
150
151 If you want to use such a RAID-4/RAID-5/RAID-6 set, say Y. To
152 compile this code as a module, choose M here: the module
153 will be called raid456.
154
155 If unsure, say Y.
156
157config MD_MULTIPATH
158 tristate "Multipath I/O support"
159 depends on BLK_DEV_MD
160 help
161 MD_MULTIPATH provides a simple multi-path personality for use
162 the MD framework. It is not under active development. New
163 projects should consider using DM_MULTIPATH which has more
164 features and more testing.
165
166 If unsure, say N.
167
168config MD_FAULTY
169 tristate "Faulty test module for MD"
170 depends on BLK_DEV_MD
171 help
172 The "faulty" module allows for a block device that occasionally returns
173 read or write errors. It is useful for testing.
174
175 In unsure, say N.
176
177source "drivers/md/bcache/Kconfig"
178
179config BLK_DEV_DM_BUILTIN
180 boolean
181
182config BLK_DEV_DM
183 tristate "Device mapper support"
184 select BLK_DEV_DM_BUILTIN
185 ---help---
186 Device-mapper is a low level volume manager. It works by allowing
187 people to specify mappings for ranges of logical sectors. Various
188 mapping types are available, in addition people may write their own
189 modules containing custom mappings if they wish.
190
191 Higher level volume managers such as LVM2 use this driver.
192
193 To compile this as a module, choose M here: the module will be
194 called dm-mod.
195
196 If unsure, say N.
197
198config DM_DEBUG
199 boolean "Device mapper debugging support"
200 depends on BLK_DEV_DM
201 ---help---
202 Enable this for messages that may help debug device-mapper problems.
203
204 If unsure, say N.
205
206config DM_BUFIO
207 tristate
208 depends on BLK_DEV_DM
209 ---help---
210 This interface allows you to do buffered I/O on a device and acts
211 as a cache, holding recently-read blocks in memory and performing
212 delayed writes.
213
214config DM_BIO_PRISON
215 tristate
216 depends on BLK_DEV_DM
217 ---help---
218 Some bio locking schemes used by other device-mapper targets
219 including thin provisioning.
220
221source "drivers/md/persistent-data/Kconfig"
222
223config DM_CRYPT
224 tristate "Crypt target support"
225 depends on BLK_DEV_DM
226 select CRYPTO
227 select CRYPTO_CBC
228 ---help---
229 This device-mapper target allows you to create a device that
230 transparently encrypts the data on it. You'll need to activate
231 the ciphers you're going to use in the cryptoapi configuration.
232
233 Information on how to use dm-crypt can be found on
234
235 <http://www.saout.de/misc/dm-crypt/>
236
237 To compile this code as a module, choose M here: the module will
238 be called dm-crypt.
239
240 If unsure, say N.
241
242config DM_SNAPSHOT
243 tristate "Snapshot target"
244 depends on BLK_DEV_DM
245 select DM_BUFIO
246 ---help---
247 Allow volume managers to take writable snapshots of a device.
248
249config DM_THIN_PROVISIONING
250 tristate "Thin provisioning target"
251 depends on BLK_DEV_DM
252 select DM_PERSISTENT_DATA
253 select DM_BIO_PRISON
254 ---help---
255 Provides thin provisioning and snapshots that share a data store.
256
257config DM_CACHE
258 tristate "Cache target (EXPERIMENTAL)"
259 depends on BLK_DEV_DM
260 default n
261 select DM_PERSISTENT_DATA
262 select DM_BIO_PRISON
263 ---help---
264 dm-cache attempts to improve performance of a block device by
265 moving frequently used data to a smaller, higher performance
266 device. Different 'policy' plugins can be used to change the
267 algorithms used to select which blocks are promoted, demoted,
268 cleaned etc. It supports writeback and writethrough modes.
269
270config DM_CACHE_MQ
271 tristate "MQ Cache Policy (EXPERIMENTAL)"
272 depends on DM_CACHE
273 default y
274 ---help---
275 A cache policy that uses a multiqueue ordered by recent hit
276 count to select which blocks should be promoted and demoted.
277 This is meant to be a general purpose policy. It prioritises
278 reads over writes.
279
280config DM_CACHE_CLEANER
281 tristate "Cleaner Cache Policy (EXPERIMENTAL)"
282 depends on DM_CACHE
283 default y
284 ---help---
285 A simple cache policy that writes back all data to the
286 origin. Used when decommissioning a dm-cache.
287
288config DM_ERA
289 tristate "Era target (EXPERIMENTAL)"
290 depends on BLK_DEV_DM
291 default n
292 select DM_PERSISTENT_DATA
293 select DM_BIO_PRISON
294 ---help---
295 dm-era tracks which parts of a block device are written to
296 over time. Useful for maintaining cache coherency when using
297 vendor snapshots.
298
299config DM_MIRROR
300 tristate "Mirror target"
301 depends on BLK_DEV_DM
302 ---help---
303 Allow volume managers to mirror logical volumes, also
304 needed for live data migration tools such as 'pvmove'.
305
306config DM_LOG_USERSPACE
307 tristate "Mirror userspace logging"
308 depends on DM_MIRROR && NET
309 select CONNECTOR
310 ---help---
311 The userspace logging module provides a mechanism for
312 relaying the dm-dirty-log API to userspace. Log designs
313 which are more suited to userspace implementation (e.g.
314 shared storage logs) or experimental logs can be implemented
315 by leveraging this framework.
316
317config DM_RAID
318 tristate "RAID 1/4/5/6/10 target"
319 depends on BLK_DEV_DM
320 select MD_RAID1
321 select MD_RAID10
322 select MD_RAID456
323 select BLK_DEV_MD
324 ---help---
325 A dm target that supports RAID1, RAID10, RAID4, RAID5 and RAID6 mappings
326
327 A RAID-5 set of N drives with a capacity of C MB per drive provides
328 the capacity of C * (N - 1) MB, and protects against a failure
329 of a single drive. For a given sector (row) number, (N - 1) drives
330 contain data sectors, and one drive contains the parity protection.
331 For a RAID-4 set, the parity blocks are present on a single drive,
332 while a RAID-5 set distributes the parity across the drives in one
333 of the available parity distribution methods.
334
335 A RAID-6 set of N drives with a capacity of C MB per drive
336 provides the capacity of C * (N - 2) MB, and protects
337 against a failure of any two drives. For a given sector
338 (row) number, (N - 2) drives contain data sectors, and two
339 drives contains two independent redundancy syndromes. Like
340 RAID-5, RAID-6 distributes the syndromes across the drives
341 in one of the available parity distribution methods.
342
343config DM_ZERO
344 tristate "Zero target"
345 depends on BLK_DEV_DM
346 ---help---
347 A target that discards writes, and returns all zeroes for
348 reads. Useful in some recovery situations.
349
350config DM_MULTIPATH
351 tristate "Multipath target"
352 depends on BLK_DEV_DM
353 # nasty syntax but means make DM_MULTIPATH independent
354 # of SCSI_DH if the latter isn't defined but if
355 # it is, DM_MULTIPATH must depend on it. We get a build
356 # error if SCSI_DH=m and DM_MULTIPATH=y
357 depends on SCSI_DH || !SCSI_DH
358 ---help---
359 Allow volume managers to support multipath hardware.
360
361config DM_MULTIPATH_QL
362 tristate "I/O Path Selector based on the number of in-flight I/Os"
363 depends on DM_MULTIPATH
364 ---help---
365 This path selector is a dynamic load balancer which selects
366 the path with the least number of in-flight I/Os.
367
368 If unsure, say N.
369
370config DM_MULTIPATH_ST
371 tristate "I/O Path Selector based on the service time"
372 depends on DM_MULTIPATH
373 ---help---
374 This path selector is a dynamic load balancer which selects
375 the path expected to complete the incoming I/O in the shortest
376 time.
377
378 If unsure, say N.
379
380config DM_DELAY
381 tristate "I/O delaying target"
382 depends on BLK_DEV_DM
383 ---help---
384 A target that delays reads and/or writes and can send
385 them to different devices. Useful for testing.
386
387 If unsure, say N.
388
389config DM_UEVENT
390 bool "DM uevents"
391 depends on BLK_DEV_DM
392 ---help---
393 Generate udev events for DM events.
394
395config DM_FLAKEY
396 tristate "Flakey target"
397 depends on BLK_DEV_DM
398 ---help---
399 A target that intermittently fails I/O for debugging purposes.
400
401config DM_VERITY
402 tristate "Verity target support"
403 depends on BLK_DEV_DM
404 select CRYPTO
405 select CRYPTO_HASH
406 select DM_BUFIO
407 ---help---
408 This device-mapper target creates a read-only device that
409 transparently validates the data on one underlying device against
410 a pre-generated tree of cryptographic checksums stored on a second
411 device.
412
413 You'll need to activate the digests you're going to use in the
414 cryptoapi configuration.
415
416 To compile this code as a module, choose M here: the module will
417 be called dm-verity.
418
419 If unsure, say N.
420
421config DM_SWITCH
422 tristate "Switch target support (EXPERIMENTAL)"
423 depends on BLK_DEV_DM
424 ---help---
425 This device-mapper target creates a device that supports an arbitrary
426 mapping of fixed-size regions of I/O across a fixed set of paths.
427 The path used for any specific region can be switched dynamically
428 by sending the target a message.
429
430 To compile this code as a module, choose M here: the module will
431 be called dm-switch.
432
433 If unsure, say N.
434
435endif # MD