4 * The contents of this file are subject to the terms of the
5 * Common Development and Distribution License (the "License").
6 * You may not use this file except in compliance with the License.
8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9 * or http://www.opensolaris.org/os/licensing.
10 * See the License for the specific language governing permissions
11 * and limitations under the License.
13 * When distributing Covered Code, include this CDDL HEADER in each
14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15 * If applicable, add the following below this CDDL HEADER, with the
16 * fields enclosed by brackets "[]" replaced with your own identifying
17 * information: Portions Copyright [yyyy] [name of copyright owner]
22 * Copyright 2010 Sun Microsystems, Inc. All rights reserved.
23 * Use is subject to license terms.
27 * Copyright (c) 2012, 2015 by Delphix. All rights reserved.
30 #include <sys/zfs_context.h>
32 #include <sys/vdev_impl.h>
35 #include <sys/fs/zfs.h>
40 static kstat_t
*mirror_ksp
= NULL
;
42 typedef struct mirror_stats
{
43 kstat_named_t vdev_mirror_stat_rotating_linear
;
44 kstat_named_t vdev_mirror_stat_rotating_offset
;
45 kstat_named_t vdev_mirror_stat_rotating_seek
;
46 kstat_named_t vdev_mirror_stat_non_rotating_linear
;
47 kstat_named_t vdev_mirror_stat_non_rotating_seek
;
49 kstat_named_t vdev_mirror_stat_preferred_found
;
50 kstat_named_t vdev_mirror_stat_preferred_not_found
;
53 static mirror_stats_t mirror_stats
= {
54 /* New I/O follows directly the last I/O */
55 { "rotating_linear", KSTAT_DATA_UINT64
},
56 /* New I/O is within zfs_vdev_mirror_rotating_seek_offset of the last */
57 { "rotating_offset", KSTAT_DATA_UINT64
},
58 /* New I/O requires random seek */
59 { "rotating_seek", KSTAT_DATA_UINT64
},
60 /* New I/O follows directly the last I/O (nonrot) */
61 { "non_rotating_linear", KSTAT_DATA_UINT64
},
62 /* New I/O requires random seek (nonrot) */
63 { "non_rotating_seek", KSTAT_DATA_UINT64
},
64 /* Preferred child vdev found */
65 { "preferred_found", KSTAT_DATA_UINT64
},
66 /* Preferred child vdev not found or equal load */
67 { "preferred_not_found", KSTAT_DATA_UINT64
},
71 #define MIRROR_STAT(stat) (mirror_stats.stat.value.ui64)
72 #define MIRROR_INCR(stat, val) atomic_add_64(&MIRROR_STAT(stat), val)
73 #define MIRROR_BUMP(stat) MIRROR_INCR(stat, 1)
76 vdev_mirror_stat_init(void)
78 mirror_ksp
= kstat_create("zfs", 0, "vdev_mirror_stats",
79 "misc", KSTAT_TYPE_NAMED
,
80 sizeof (mirror_stats
) / sizeof (kstat_named_t
), KSTAT_FLAG_VIRTUAL
);
81 if (mirror_ksp
!= NULL
) {
82 mirror_ksp
->ks_data
= &mirror_stats
;
83 kstat_install(mirror_ksp
);
88 vdev_mirror_stat_fini(void)
90 if (mirror_ksp
!= NULL
) {
91 kstat_delete(mirror_ksp
);
97 * Virtual device vector for mirroring.
100 typedef struct mirror_child
{
107 uint8_t mc_speculative
;
110 typedef struct mirror_map
{
112 int mm_preferred_cnt
;
114 boolean_t mm_replacing
;
116 mirror_child_t mm_child
[];
119 static int vdev_mirror_shift
= 21;
122 * The load configuration settings below are tuned by default for
123 * the case where all devices are of the same rotational type.
125 * If there is a mixture of rotating and non-rotating media, setting
126 * zfs_vdev_mirror_non_rotating_seek_inc to 0 may well provide better results
127 * as it will direct more reads to the non-rotating vdevs which are more likely
128 * to have a higher performance.
131 /* Rotating media load calculation configuration. */
132 static int zfs_vdev_mirror_rotating_inc
= 0;
133 static int zfs_vdev_mirror_rotating_seek_inc
= 5;
134 static int zfs_vdev_mirror_rotating_seek_offset
= 1 * 1024 * 1024;
136 /* Non-rotating media load calculation configuration. */
137 static int zfs_vdev_mirror_non_rotating_inc
= 0;
138 static int zfs_vdev_mirror_non_rotating_seek_inc
= 1;
141 vdev_mirror_map_size(int children
)
143 return (offsetof(mirror_map_t
, mm_child
[children
]) +
144 sizeof (int) * children
);
147 static inline mirror_map_t
*
148 vdev_mirror_map_alloc(int children
, boolean_t replacing
, boolean_t root
)
152 mm
= kmem_zalloc(vdev_mirror_map_size(children
), KM_SLEEP
);
153 mm
->mm_children
= children
;
154 mm
->mm_replacing
= replacing
;
156 mm
->mm_preferred
= (int *)((uintptr_t)mm
+
157 offsetof(mirror_map_t
, mm_child
[children
]));
163 vdev_mirror_map_free(zio_t
*zio
)
165 mirror_map_t
*mm
= zio
->io_vsd
;
167 kmem_free(mm
, vdev_mirror_map_size(mm
->mm_children
));
170 static const zio_vsd_ops_t vdev_mirror_vsd_ops
= {
171 .vsd_free
= vdev_mirror_map_free
,
172 .vsd_cksum_report
= zio_vsd_default_cksum_report
176 vdev_mirror_load(mirror_map_t
*mm
, vdev_t
*vd
, uint64_t zio_offset
)
178 uint64_t last_offset
;
182 /* All DVAs have equal weight at the root. */
187 * We don't return INT_MAX if the device is resilvering i.e.
188 * vdev_resilver_txg != 0 as when tested performance was slightly
189 * worse overall when resilvering with compared to without.
192 /* Fix zio_offset for leaf vdevs */
193 if (vd
->vdev_ops
->vdev_op_leaf
)
194 zio_offset
+= VDEV_LABEL_START_SIZE
;
196 /* Standard load based on pending queue length. */
197 load
= vdev_queue_length(vd
);
198 last_offset
= vdev_queue_last_offset(vd
);
200 if (vd
->vdev_nonrot
) {
201 /* Non-rotating media. */
202 if (last_offset
== zio_offset
) {
203 MIRROR_BUMP(vdev_mirror_stat_non_rotating_linear
);
204 return (load
+ zfs_vdev_mirror_non_rotating_inc
);
208 * Apply a seek penalty even for non-rotating devices as
209 * sequential I/O's can be aggregated into fewer operations on
210 * the device, thus avoiding unnecessary per-command overhead
211 * and boosting performance.
213 MIRROR_BUMP(vdev_mirror_stat_non_rotating_seek
);
214 return (load
+ zfs_vdev_mirror_non_rotating_seek_inc
);
217 /* Rotating media I/O's which directly follow the last I/O. */
218 if (last_offset
== zio_offset
) {
219 MIRROR_BUMP(vdev_mirror_stat_rotating_linear
);
220 return (load
+ zfs_vdev_mirror_rotating_inc
);
224 * Apply half the seek increment to I/O's within seek offset
225 * of the last I/O issued to this vdev as they should incur less
226 * of a seek increment.
228 offset_diff
= (int64_t)(last_offset
- zio_offset
);
229 if (ABS(offset_diff
) < zfs_vdev_mirror_rotating_seek_offset
) {
230 MIRROR_BUMP(vdev_mirror_stat_rotating_offset
);
231 return (load
+ (zfs_vdev_mirror_rotating_seek_inc
/ 2));
234 /* Apply the full seek increment to all other I/O's. */
235 MIRROR_BUMP(vdev_mirror_stat_rotating_seek
);
236 return (load
+ zfs_vdev_mirror_rotating_seek_inc
);
240 * Avoid inlining the function to keep vdev_mirror_io_start(), which
241 * is this functions only caller, as small as possible on the stack.
243 noinline
static mirror_map_t
*
244 vdev_mirror_map_init(zio_t
*zio
)
246 mirror_map_t
*mm
= NULL
;
248 vdev_t
*vd
= zio
->io_vd
;
252 dva_t
*dva
= zio
->io_bp
->blk_dva
;
253 spa_t
*spa
= zio
->io_spa
;
254 dva_t dva_copy
[SPA_DVAS_PER_BP
];
256 c
= BP_GET_NDVAS(zio
->io_bp
);
259 * If we do not trust the pool config, some DVAs might be
260 * invalid or point to vdevs that do not exist. We skip them.
262 if (!spa_trust_config(spa
)) {
263 ASSERT3U(zio
->io_type
, ==, ZIO_TYPE_READ
);
265 for (int i
= 0; i
< c
; i
++) {
266 if (zfs_dva_valid(spa
, &dva
[i
], zio
->io_bp
))
267 dva_copy
[j
++] = dva
[i
];
271 zio
->io_error
= ENXIO
;
280 mm
= vdev_mirror_map_alloc(c
, B_FALSE
, B_TRUE
);
281 for (c
= 0; c
< mm
->mm_children
; c
++) {
282 mc
= &mm
->mm_child
[c
];
284 mc
->mc_vd
= vdev_lookup_top(spa
, DVA_GET_VDEV(&dva
[c
]));
285 mc
->mc_offset
= DVA_GET_OFFSET(&dva
[c
]);
288 mm
= vdev_mirror_map_alloc(vd
->vdev_children
,
289 (vd
->vdev_ops
== &vdev_replacing_ops
||
290 vd
->vdev_ops
== &vdev_spare_ops
), B_FALSE
);
291 for (c
= 0; c
< mm
->mm_children
; c
++) {
292 mc
= &mm
->mm_child
[c
];
293 mc
->mc_vd
= vd
->vdev_child
[c
];
294 mc
->mc_offset
= zio
->io_offset
;
299 zio
->io_vsd_ops
= &vdev_mirror_vsd_ops
;
304 vdev_mirror_open(vdev_t
*vd
, uint64_t *asize
, uint64_t *max_asize
,
310 if (vd
->vdev_children
== 0) {
311 vd
->vdev_stat
.vs_aux
= VDEV_AUX_BAD_LABEL
;
312 return (SET_ERROR(EINVAL
));
315 vdev_open_children(vd
);
317 for (int c
= 0; c
< vd
->vdev_children
; c
++) {
318 vdev_t
*cvd
= vd
->vdev_child
[c
];
320 if (cvd
->vdev_open_error
) {
321 lasterror
= cvd
->vdev_open_error
;
326 *asize
= MIN(*asize
- 1, cvd
->vdev_asize
- 1) + 1;
327 *max_asize
= MIN(*max_asize
- 1, cvd
->vdev_max_asize
- 1) + 1;
328 *ashift
= MAX(*ashift
, cvd
->vdev_ashift
);
331 if (numerrors
== vd
->vdev_children
) {
332 if (vdev_children_are_offline(vd
))
333 vd
->vdev_stat
.vs_aux
= VDEV_AUX_CHILDREN_OFFLINE
;
335 vd
->vdev_stat
.vs_aux
= VDEV_AUX_NO_REPLICAS
;
343 vdev_mirror_close(vdev_t
*vd
)
345 for (int c
= 0; c
< vd
->vdev_children
; c
++)
346 vdev_close(vd
->vdev_child
[c
]);
350 vdev_mirror_child_done(zio_t
*zio
)
352 mirror_child_t
*mc
= zio
->io_private
;
354 mc
->mc_error
= zio
->io_error
;
360 vdev_mirror_scrub_done(zio_t
*zio
)
362 mirror_child_t
*mc
= zio
->io_private
;
364 if (zio
->io_error
== 0) {
366 zio_link_t
*zl
= NULL
;
368 mutex_enter(&zio
->io_lock
);
369 while ((pio
= zio_walk_parents(zio
, &zl
)) != NULL
) {
370 mutex_enter(&pio
->io_lock
);
371 ASSERT3U(zio
->io_size
, >=, pio
->io_size
);
372 abd_copy(pio
->io_abd
, zio
->io_abd
, pio
->io_size
);
373 mutex_exit(&pio
->io_lock
);
375 mutex_exit(&zio
->io_lock
);
378 abd_free(zio
->io_abd
);
380 mc
->mc_error
= zio
->io_error
;
386 * Check the other, lower-index DVAs to see if they're on the same
387 * vdev as the child we picked. If they are, use them since they
388 * are likely to have been allocated from the primary metaslab in
389 * use at the time, and hence are more likely to have locality with
393 vdev_mirror_dva_select(zio_t
*zio
, int p
)
395 dva_t
*dva
= zio
->io_bp
->blk_dva
;
396 mirror_map_t
*mm
= zio
->io_vsd
;
400 preferred
= mm
->mm_preferred
[p
];
401 for (p
--; p
>= 0; p
--) {
402 c
= mm
->mm_preferred
[p
];
403 if (DVA_GET_VDEV(&dva
[c
]) == DVA_GET_VDEV(&dva
[preferred
]))
410 vdev_mirror_preferred_child_randomize(zio_t
*zio
)
412 mirror_map_t
*mm
= zio
->io_vsd
;
416 p
= spa_get_random(mm
->mm_preferred_cnt
);
417 return (vdev_mirror_dva_select(zio
, p
));
421 * To ensure we don't always favour the first matching vdev,
422 * which could lead to wear leveling issues on SSD's, we
423 * use the I/O offset as a pseudo random seed into the vdevs
424 * which have the lowest load.
426 p
= (zio
->io_offset
>> vdev_mirror_shift
) % mm
->mm_preferred_cnt
;
427 return (mm
->mm_preferred
[p
]);
431 * Try to find a vdev whose DTL doesn't contain the block we want to read
432 * prefering vdevs based on determined load.
434 * Try to find a child whose DTL doesn't contain the block we want to read.
435 * If we can't, try the read on any vdev we haven't already tried.
438 vdev_mirror_child_select(zio_t
*zio
)
440 mirror_map_t
*mm
= zio
->io_vsd
;
441 uint64_t txg
= zio
->io_txg
;
444 ASSERT(zio
->io_bp
== NULL
|| BP_PHYSICAL_BIRTH(zio
->io_bp
) == txg
);
446 lowest_load
= INT_MAX
;
447 mm
->mm_preferred_cnt
= 0;
448 for (c
= 0; c
< mm
->mm_children
; c
++) {
451 mc
= &mm
->mm_child
[c
];
452 if (mc
->mc_tried
|| mc
->mc_skipped
)
455 if (mc
->mc_vd
== NULL
|| !vdev_readable(mc
->mc_vd
)) {
456 mc
->mc_error
= SET_ERROR(ENXIO
);
457 mc
->mc_tried
= 1; /* don't even try */
462 if (vdev_dtl_contains(mc
->mc_vd
, DTL_MISSING
, txg
, 1)) {
463 mc
->mc_error
= SET_ERROR(ESTALE
);
465 mc
->mc_speculative
= 1;
469 mc
->mc_load
= vdev_mirror_load(mm
, mc
->mc_vd
, mc
->mc_offset
);
470 if (mc
->mc_load
> lowest_load
)
473 if (mc
->mc_load
< lowest_load
) {
474 lowest_load
= mc
->mc_load
;
475 mm
->mm_preferred_cnt
= 0;
477 mm
->mm_preferred
[mm
->mm_preferred_cnt
] = c
;
478 mm
->mm_preferred_cnt
++;
481 if (mm
->mm_preferred_cnt
== 1) {
482 MIRROR_BUMP(vdev_mirror_stat_preferred_found
);
483 return (mm
->mm_preferred
[0]);
486 if (mm
->mm_preferred_cnt
> 1) {
487 MIRROR_BUMP(vdev_mirror_stat_preferred_not_found
);
488 return (vdev_mirror_preferred_child_randomize(zio
));
492 * Every device is either missing or has this txg in its DTL.
493 * Look for any child we haven't already tried before giving up.
495 for (c
= 0; c
< mm
->mm_children
; c
++) {
496 if (!mm
->mm_child
[c
].mc_tried
)
501 * Every child failed. There's no place left to look.
507 vdev_mirror_io_start(zio_t
*zio
)
513 mm
= vdev_mirror_map_init(zio
);
516 ASSERT(!spa_trust_config(zio
->io_spa
));
517 ASSERT(zio
->io_type
== ZIO_TYPE_READ
);
522 if (zio
->io_type
== ZIO_TYPE_READ
) {
523 if (zio
->io_bp
!= NULL
&&
524 (zio
->io_flags
& ZIO_FLAG_SCRUB
) && !mm
->mm_replacing
) {
526 * For scrubbing reads (if we can verify the
527 * checksum here, as indicated by io_bp being
528 * non-NULL) we need to allocate a read buffer for
529 * each child and issue reads to all children. If
530 * any child succeeds, it will copy its data into
531 * zio->io_data in vdev_mirror_scrub_done.
533 for (c
= 0; c
< mm
->mm_children
; c
++) {
534 mc
= &mm
->mm_child
[c
];
535 zio_nowait(zio_vdev_child_io(zio
, zio
->io_bp
,
536 mc
->mc_vd
, mc
->mc_offset
,
537 abd_alloc_sametype(zio
->io_abd
,
538 zio
->io_size
), zio
->io_size
,
539 zio
->io_type
, zio
->io_priority
, 0,
540 vdev_mirror_scrub_done
, mc
));
546 * For normal reads just pick one child.
548 c
= vdev_mirror_child_select(zio
);
551 ASSERT(zio
->io_type
== ZIO_TYPE_WRITE
);
554 * Writes go to all children.
557 children
= mm
->mm_children
;
561 mc
= &mm
->mm_child
[c
];
562 zio_nowait(zio_vdev_child_io(zio
, zio
->io_bp
,
563 mc
->mc_vd
, mc
->mc_offset
, zio
->io_abd
, zio
->io_size
,
564 zio
->io_type
, zio
->io_priority
, 0,
565 vdev_mirror_child_done
, mc
));
573 vdev_mirror_worst_error(mirror_map_t
*mm
)
575 int error
[2] = { 0, 0 };
577 for (int c
= 0; c
< mm
->mm_children
; c
++) {
578 mirror_child_t
*mc
= &mm
->mm_child
[c
];
579 int s
= mc
->mc_speculative
;
580 error
[s
] = zio_worst_error(error
[s
], mc
->mc_error
);
583 return (error
[0] ? error
[0] : error
[1]);
587 vdev_mirror_io_done(zio_t
*zio
)
589 mirror_map_t
*mm
= zio
->io_vsd
;
593 int unexpected_errors
= 0;
598 for (c
= 0; c
< mm
->mm_children
; c
++) {
599 mc
= &mm
->mm_child
[c
];
604 } else if (mc
->mc_tried
) {
609 if (zio
->io_type
== ZIO_TYPE_WRITE
) {
611 * XXX -- for now, treat partial writes as success.
613 * Now that we support write reallocation, it would be better
614 * to treat partial failure as real failure unless there are
615 * no non-degraded top-level vdevs left, and not update DTLs
616 * if we intend to reallocate.
619 if (good_copies
!= mm
->mm_children
) {
621 * Always require at least one good copy.
623 * For ditto blocks (io_vd == NULL), require
624 * all copies to be good.
626 * XXX -- for replacing vdevs, there's no great answer.
627 * If the old device is really dead, we may not even
628 * be able to access it -- so we only want to
629 * require good writes to the new device. But if
630 * the new device turns out to be flaky, we want
631 * to be able to detach it -- which requires all
632 * writes to the old device to have succeeded.
634 if (good_copies
== 0 || zio
->io_vd
== NULL
)
635 zio
->io_error
= vdev_mirror_worst_error(mm
);
640 ASSERT(zio
->io_type
== ZIO_TYPE_READ
);
643 * If we don't have a good copy yet, keep trying other children.
646 if (good_copies
== 0 && (c
= vdev_mirror_child_select(zio
)) != -1) {
647 ASSERT(c
>= 0 && c
< mm
->mm_children
);
648 mc
= &mm
->mm_child
[c
];
649 zio_vdev_io_redone(zio
);
650 zio_nowait(zio_vdev_child_io(zio
, zio
->io_bp
,
651 mc
->mc_vd
, mc
->mc_offset
, zio
->io_abd
, zio
->io_size
,
652 ZIO_TYPE_READ
, zio
->io_priority
, 0,
653 vdev_mirror_child_done
, mc
));
658 if (good_copies
== 0) {
659 zio
->io_error
= vdev_mirror_worst_error(mm
);
660 ASSERT(zio
->io_error
!= 0);
663 if (good_copies
&& spa_writeable(zio
->io_spa
) &&
664 (unexpected_errors
||
665 (zio
->io_flags
& ZIO_FLAG_RESILVER
) ||
666 ((zio
->io_flags
& ZIO_FLAG_SCRUB
) && mm
->mm_replacing
))) {
668 * Use the good data we have in hand to repair damaged children.
670 for (c
= 0; c
< mm
->mm_children
; c
++) {
672 * Don't rewrite known good children.
673 * Not only is it unnecessary, it could
674 * actually be harmful: if the system lost
675 * power while rewriting the only good copy,
676 * there would be no good copies left!
678 mc
= &mm
->mm_child
[c
];
680 if (mc
->mc_error
== 0) {
684 * We didn't try this child. We need to
686 * 1. it's a scrub (in which case we have
687 * tried everything that was healthy)
689 * 2. it's an indirect vdev (in which case
690 * it could point to any other vdev, which
691 * might have a bad DTL)
693 * 3. the DTL indicates that this data is
694 * missing from this vdev
696 if (!(zio
->io_flags
& ZIO_FLAG_SCRUB
) &&
697 mc
->mc_vd
->vdev_ops
!= &vdev_indirect_ops
&&
698 !vdev_dtl_contains(mc
->mc_vd
, DTL_PARTIAL
,
701 mc
->mc_error
= SET_ERROR(ESTALE
);
704 zio_nowait(zio_vdev_child_io(zio
, zio
->io_bp
,
705 mc
->mc_vd
, mc
->mc_offset
,
706 zio
->io_abd
, zio
->io_size
,
707 ZIO_TYPE_WRITE
, ZIO_PRIORITY_ASYNC_WRITE
,
708 ZIO_FLAG_IO_REPAIR
| (unexpected_errors
?
709 ZIO_FLAG_SELF_HEAL
: 0), NULL
, NULL
));
715 vdev_mirror_state_change(vdev_t
*vd
, int faulted
, int degraded
)
717 if (faulted
== vd
->vdev_children
) {
718 if (vdev_children_are_offline(vd
)) {
719 vdev_set_state(vd
, B_FALSE
, VDEV_STATE_OFFLINE
,
720 VDEV_AUX_CHILDREN_OFFLINE
);
722 vdev_set_state(vd
, B_FALSE
, VDEV_STATE_CANT_OPEN
,
723 VDEV_AUX_NO_REPLICAS
);
725 } else if (degraded
+ faulted
!= 0) {
726 vdev_set_state(vd
, B_FALSE
, VDEV_STATE_DEGRADED
, VDEV_AUX_NONE
);
728 vdev_set_state(vd
, B_FALSE
, VDEV_STATE_HEALTHY
, VDEV_AUX_NONE
);
732 vdev_ops_t vdev_mirror_ops
= {
736 vdev_mirror_io_start
,
738 vdev_mirror_state_change
,
744 VDEV_TYPE_MIRROR
, /* name of this vdev type */
745 B_FALSE
/* not a leaf vdev */
748 vdev_ops_t vdev_replacing_ops
= {
752 vdev_mirror_io_start
,
754 vdev_mirror_state_change
,
760 VDEV_TYPE_REPLACING
, /* name of this vdev type */
761 B_FALSE
/* not a leaf vdev */
764 vdev_ops_t vdev_spare_ops
= {
768 vdev_mirror_io_start
,
770 vdev_mirror_state_change
,
776 VDEV_TYPE_SPARE
, /* name of this vdev type */
777 B_FALSE
/* not a leaf vdev */
782 module_param(zfs_vdev_mirror_rotating_inc
, int, 0644);
783 MODULE_PARM_DESC(zfs_vdev_mirror_rotating_inc
,
784 "Rotating media load increment for non-seeking I/O's");
786 module_param(zfs_vdev_mirror_rotating_seek_inc
, int, 0644);
787 MODULE_PARM_DESC(zfs_vdev_mirror_rotating_seek_inc
,
788 "Rotating media load increment for seeking I/O's");
790 module_param(zfs_vdev_mirror_rotating_seek_offset
, int, 0644);
792 MODULE_PARM_DESC(zfs_vdev_mirror_rotating_seek_offset
,
793 "Offset in bytes from the last I/O which "
794 "triggers a reduced rotating media seek increment");
796 module_param(zfs_vdev_mirror_non_rotating_inc
, int, 0644);
797 MODULE_PARM_DESC(zfs_vdev_mirror_non_rotating_inc
,
798 "Non-rotating media load increment for non-seeking I/O's");
800 module_param(zfs_vdev_mirror_non_rotating_seek_inc
, int, 0644);
801 MODULE_PARM_DESC(zfs_vdev_mirror_non_rotating_seek_inc
,
802 "Non-rotating media load increment for seeking I/O's");