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Explain the read-balancing algorithm for RAID1 better in md.4
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1 /*
2 * mdadm - manage Linux "md" devices aka RAID arrays.
3 *
4 * Copyright (C) 2001-2006 Neil Brown <neilb@suse.de>
5 *
6 *
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License as published by
9 * the Free Software Foundation; either version 2 of the License, or
10 * (at your option) any later version.
11 *
12 * This program is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 * GNU General Public License for more details.
16 *
17 * You should have received a copy of the GNU General Public License
18 * along with this program; if not, write to the Free Software
19 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
20 *
21 * Author: Neil Brown
22 * Email: <neilb@cse.unsw.edu.au>
23 * Paper: Neil Brown
24 * School of Computer Science and Engineering
25 * The University of New South Wales
26 * Sydney, 2052
27 * Australia
28 */
29
30 #include "mdadm.h"
31 #include "md_p.h"
32 #include "md_u.h"
33
34 int Detail(char *dev, int brief, int export, int test, char *homehost)
35 {
36 /*
37 * Print out details for an md array by using
38 * GET_ARRAY_INFO and GET_DISK_INFO ioctl calls
39 */
40
41 int fd = open(dev, O_RDONLY, 0);
42 int vers;
43 mdu_array_info_t array;
44 mdu_disk_info_t *disks;
45 int next;
46 int d;
47 time_t atime;
48 char *c;
49 char *devices = NULL;
50 int spares = 0;
51 struct stat stb;
52 int is_26 = get_linux_version() >= 2006000;
53 int is_rebuilding = 0;
54 int failed = 0;
55 struct supertype *st = NULL;
56 int max_disks = MD_SB_DISKS; /* just a default */
57 struct mdinfo info;
58
59 void *super = NULL;
60 int rv = test ? 4 : 1;
61 int avail_disks = 0;
62 char *avail;
63
64 if (fd < 0) {
65 fprintf(stderr, Name ": cannot open %s: %s\n",
66 dev, strerror(errno));
67 return rv;
68 }
69 vers = md_get_version(fd);
70 if (vers < 0) {
71 fprintf(stderr, Name ": %s does not appear to be an md device\n",
72 dev);
73 close(fd);
74 return rv;
75 }
76 if (vers < 9000) {
77 fprintf(stderr, Name ": cannot get detail for md device %s: driver version too old.\n",
78 dev);
79 close(fd);
80 return rv;
81 }
82 if (ioctl(fd, GET_ARRAY_INFO, &array)<0) {
83 if (errno == ENODEV)
84 fprintf(stderr, Name ": md device %s does not appear to be active.\n",
85 dev);
86 else
87 fprintf(stderr, Name ": cannot get array detail for %s: %s\n",
88 dev, strerror(errno));
89 close(fd);
90 return rv;
91 }
92 st = super_by_version(array.major_version, array.minor_version);
93
94 if (fstat(fd, &stb) != 0 && !S_ISBLK(stb.st_mode))
95 stb.st_rdev = 0;
96 rv = 0;
97
98 if (st) max_disks = st->max_devs;
99
100 /* try to load a superblock */
101 for (d= 0; d<max_disks; d++) {
102 mdu_disk_info_t disk;
103 char *dv;
104 disk.number = d;
105 if (ioctl(fd, GET_DISK_INFO, &disk) < 0)
106 continue;
107 if (d >= array.raid_disks &&
108 disk.major == 0 &&
109 disk.minor == 0)
110 continue;
111 if ((dv=map_dev(disk.major, disk.minor, 1))) {
112 if (!super && (disk.state & (1<<MD_DISK_ACTIVE))) {
113 /* try to read the superblock from this device
114 * to get more info
115 */
116 int fd2 = dev_open(dv, O_RDONLY);
117 if (fd2 >=0 && st &&
118 st->ss->load_super(st, fd2, &super, NULL) == 0) {
119 st->ss->getinfo_super(&info, super);
120 if (info.array.ctime != array.ctime ||
121 info.array.level != array.level) {
122 free(super);
123 super = NULL;
124 }
125 }
126 if (fd2 >= 0) close(fd2);
127 }
128 }
129 }
130
131 /* Ok, we have some info to print... */
132 c = map_num(pers, array.level);
133
134 if (export) {
135 if (c)
136 printf("MD_LEVEL=%s\n", c);
137 printf("MD_DEVICES=%d\n", array.raid_disks);
138 printf("MD_METADATA=%d.%d\n", array.major_version,
139 array.minor_version);
140 if (super)
141 st->ss->export_super(super);
142 goto out;
143 }
144
145 if (brief)
146 printf("ARRAY %s level=%s num-devices=%d", dev, c?c:"-unknown-",array.raid_disks );
147 else {
148 mdu_bitmap_file_t bmf;
149 unsigned long long larray_size;
150 struct mdstat_ent *ms = mdstat_read(0, 0);
151 struct mdstat_ent *e;
152 int devnum = array.md_minor;
153 if (major(stb.st_rdev) != MD_MAJOR)
154 devnum = -1 - devnum;
155
156 for (e=ms; e; e=e->next)
157 if (e->devnum == devnum)
158 break;
159 if (!get_dev_size(fd, NULL, &larray_size))
160 larray_size = 0;
161
162 printf("%s:\n", dev);
163 printf(" Version : %02d.%02d.%02d\n",
164 array.major_version, array.minor_version, array.patch_version);
165 atime = array.ctime;
166 printf(" Creation Time : %.24s\n", ctime(&atime));
167 printf(" Raid Level : %s\n", c?c:"-unknown-");
168 if (larray_size)
169 printf(" Array Size : %llu%s\n", (larray_size>>10), human_size(larray_size));
170 if (array.level >= 1) {
171 if (array.major_version != 0 &&
172 (larray_size >= 0xFFFFFFFFULL|| array.size == 0)) {
173 unsigned long long dsize = get_component_size(fd);
174 if (dsize > 0)
175 printf(" Used Dev Size : %llu%s\n",
176 dsize,
177 human_size((long long)array.size<<10));
178 else
179 printf(" Used Dev Size : unknown\n");
180 } else
181 printf(" Used Dev Size : %d%s\n", array.size,
182 human_size((long long)array.size<<10));
183 }
184 printf(" Raid Devices : %d\n", array.raid_disks);
185 printf(" Total Devices : %d\n", array.nr_disks);
186 printf("Preferred Minor : %d\n", array.md_minor);
187 printf(" Persistence : Superblock is %spersistent\n",
188 array.not_persistent?"not ":"");
189 printf("\n");
190 /* Only try GET_BITMAP_FILE for 0.90.01 and later */
191 if (vers >= 9001 &&
192 ioctl(fd, GET_BITMAP_FILE, &bmf) == 0 &&
193 bmf.pathname[0]) {
194 printf(" Intent Bitmap : %s\n", bmf.pathname);
195 printf("\n");
196 } else if (array.state & (1<<MD_SB_BITMAP_PRESENT))
197 printf(" Intent Bitmap : Internal\n\n");
198 atime = array.utime;
199 printf(" Update Time : %.24s\n", ctime(&atime));
200 printf(" State : %s%s%s%s\n",
201 (array.state&(1<<MD_SB_CLEAN))?"clean":"active",
202 array.active_disks < array.raid_disks? ", degraded":"",
203 (!e || e->percent < 0) ? "" :
204 (e->resync) ? ", resyncing": ", recovering",
205 larray_size ? "": ", Not Started");
206 printf(" Active Devices : %d\n", array.active_disks);
207 printf("Working Devices : %d\n", array.working_disks);
208 printf(" Failed Devices : %d\n", array.failed_disks);
209 printf(" Spare Devices : %d\n", array.spare_disks);
210 printf("\n");
211 if (array.level == 5) {
212 c = map_num(r5layout, array.layout);
213 printf(" Layout : %s\n", c?c:"-unknown-");
214 }
215 if (array.level == 10) {
216 printf(" Layout : near=%d, %s=%d\n",
217 array.layout&255, (array.layout&0x10000)?"offset":"far",
218 (array.layout>>8)&255);
219 }
220 switch (array.level) {
221 case 0:
222 case 4:
223 case 5:
224 case 10:
225 case 6:
226 printf(" Chunk Size : %dK\n\n", array.chunk_size/1024);
227 break;
228 case -1:
229 printf(" Rounding : %dK\n\n", array.chunk_size/1024);
230 break;
231 default: break;
232 }
233
234 if (e && e->percent >= 0) {
235 printf(" Re%s Status : %d%% complete\n",
236 (super && info.reshape_active)? "shape":"build",
237 e->percent);
238 is_rebuilding = 1;
239 }
240 free_mdstat(ms);
241
242 if (super && info.reshape_active) {
243 #if 0
244 This is pretty boring
245 printf(" Reshape pos'n : %llu%s\n", (unsigned long long) info.reshape_progress<<9,
246 human_size(info.reshape_progress<<9));
247 #endif
248 if (info.delta_disks > 0)
249 printf(" Delta Devices : %d, (%d->%d)\n",
250 info.delta_disks, array.raid_disks - info.delta_disks, array.raid_disks);
251 if (info.delta_disks < 0)
252 printf(" Delta Devices : %d, (%d->%d)\n",
253 info.delta_disks, array.raid_disks, array.raid_disks + info.delta_disks);
254 if (info.new_level != array.level) {
255 char *c = map_num(pers, info.new_level);
256 printf(" New Level : %s\n", c?c:"-unknown-");
257 }
258 if (info.new_level != array.level ||
259 info.new_layout != array.layout) {
260 if (info.new_level == 5) {
261 char *c = map_num(r5layout, info.new_layout);
262 printf(" New Layout : %s\n",
263 c?c:"-unknown-");
264 }
265 if (info.new_level == 10) {
266 printf(" New Layout : near=%d, %s=%d\n",
267 info.new_layout&255,
268 (info.new_layout&0x10000)?"offset":"far",
269 (info.new_layout>>8)&255);
270 }
271 }
272 if (info.new_chunk != array.chunk_size)
273 printf(" New Chunksize : %dK\n", info.new_chunk/1024);
274 printf("\n");
275 } else if (e && e->percent >= 0)
276 printf("\n");
277 if (super && st)
278 st->ss->detail_super(super, homehost);
279
280 printf(" Number Major Minor RaidDevice State\n");
281 }
282 disks = malloc(max_disks * sizeof(mdu_disk_info_t));
283 for (d=0; d<max_disks; d++) {
284 disks[d].state = (1<<MD_DISK_REMOVED);
285 disks[d].major = disks[d].minor = 0;
286 disks[d].number = disks[d].raid_disk = d;
287 }
288
289 next = array.raid_disks;
290 for (d=0; d < max_disks; d++) {
291 mdu_disk_info_t disk;
292 disk.number = d;
293 if (ioctl(fd, GET_DISK_INFO, &disk) < 0) {
294 if (d < array.raid_disks)
295 fprintf(stderr, Name ": cannot get device detail for device %d: %s\n",
296 d, strerror(errno));
297 continue;
298 }
299 if (disk.major == 0 && disk.minor == 0)
300 continue;
301 if (disk.raid_disk >= 0 && disk.raid_disk < array.raid_disks)
302 disks[disk.raid_disk] = disk;
303 else if (next < max_disks)
304 disks[next++] = disk;
305 }
306
307 avail = calloc(array.raid_disks, 1);
308 for (d= 0; d < max_disks; d++) {
309 char *dv;
310 mdu_disk_info_t disk = disks[d];
311
312 if (d >= array.raid_disks &&
313 disk.major == 0 &&
314 disk.minor == 0)
315 continue;
316 if (!brief) {
317 if (d == array.raid_disks) printf("\n");
318 if (disk.raid_disk < 0)
319 printf(" %5d %5d %5d - ",
320 disk.number, disk.major, disk.minor);
321 else
322 printf(" %5d %5d %5d %5d ",
323 disk.number, disk.major, disk.minor, disk.raid_disk);
324 if (disk.state & (1<<MD_DISK_FAULTY)) {
325 printf(" faulty");
326 if (disk.raid_disk < array.raid_disks &&
327 disk.raid_disk >= 0)
328 failed++;
329 }
330 if (disk.state & (1<<MD_DISK_ACTIVE)) printf(" active");
331 if (disk.state & (1<<MD_DISK_SYNC)) printf(" sync");
332 if (disk.state & (1<<MD_DISK_REMOVED)) printf(" removed");
333 if (disk.state & (1<<MD_DISK_WRITEMOSTLY)) printf(" writemostly");
334 if ((disk.state &
335 ((1<<MD_DISK_ACTIVE)|(1<<MD_DISK_SYNC)|(1<<MD_DISK_REMOVED)))
336 == 0) {
337 printf(" spare");
338 if (is_26) {
339 if (disk.raid_disk < array.raid_disks && disk.raid_disk >= 0)
340 printf(" rebuilding");
341 } else if (is_rebuilding && failed) {
342 /* Taking a bit of a risk here, we remove the
343 * device from the array, and then put it back.
344 * If this fails, we are rebuilding
345 */
346 int err = ioctl(fd, HOT_REMOVE_DISK, makedev(disk.major, disk.minor));
347 if (err == 0) ioctl(fd, HOT_ADD_DISK, makedev(disk.major, disk.minor));
348 if (err && errno == EBUSY)
349 printf(" rebuilding");
350 }
351 }
352 }
353 if (disk.state == 0) spares++;
354 if (test && d < array.raid_disks
355 && !(disk.state & (1<<MD_DISK_SYNC)))
356 rv |= 1;
357 if (d < array.raid_disks
358 && (disk.state & (1<<MD_DISK_SYNC))) {
359 avail_disks ++;
360 avail[d] = 1;
361 }
362 if ((dv=map_dev(disk.major, disk.minor, 0))) {
363 if (brief) {
364 if (devices) {
365 devices = realloc(devices,
366 strlen(devices)+1+strlen(dv)+1);
367 strcat(strcat(devices,","),dv);
368 } else
369 devices = strdup(dv);
370 } else
371 printf(" %s", dv);
372 }
373 if (!brief) printf("\n");
374 }
375 if (spares && brief) printf(" spares=%d", spares);
376 if (super && brief && st)
377 st->ss->brief_detail_super(super);
378
379 if (brief > 1 && devices) printf("\n devices=%s", devices);
380 if (brief) printf("\n");
381 if (test &&
382 !enough(array.level, array.raid_disks, array.layout,
383 1, avail, avail_disks))
384 rv = 2;
385
386 out:
387 close(fd);
388 return rv;
389 }