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authorLinus Torvalds <torvalds@linux-foundation.org>2016-07-26 17:12:11 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2016-07-26 17:12:11 -0700
commitf7e68169941a26cb1ad764d53ef13721e6fe439a (patch)
treecfcf45c75423c97c94c3932b2685890ded197711 /Documentation
parent3fc9d690936fb2e20e180710965ba2cc3a0881f8 (diff)
parentb5ab4a9ba5574430870391e93b125ada31217c4c (diff)
Merge tag 'dm-4.8-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm
Pull device mapper updates from Mike Snitzer: - initially based on Jens' 'for-4.8/core' (given all the flag churn) and later merged with 'for-4.8/core' to pickup the QUEUE_FLAG_DAX commits that DM depends on to provide its DAX support - clean up the bio-based vs request-based DM core code by moving the request-based DM core code out to dm-rq.[hc] - reinstate bio-based support in the DM multipath target (done with the idea that fast storage like NVMe over Fabrics could benefit) -- while preserving support for request_fn and blk-mq request-based DM mpath - SCSI and DM multipath persistent reservation fixes that were coordinated with Martin Petersen. - the DM raid target saw the most extensive change this cycle; it now provides reshape and takeover support (by layering ontop of the corresponding MD capabilities) - DAX support for DM core and the linear, stripe and error targets - a DM thin-provisioning block discard vs allocation race fix that addresses potential for corruption - a stable fix for DM verity-fec's block calculation during decode - a few cleanups and fixes to DM core and various targets * tag 'dm-4.8-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm: (73 commits) dm: allow bio-based table to be upgraded to bio-based with DAX support dm snap: add fake origin_direct_access dm stripe: add DAX support dm error: add DAX support dm linear: add DAX support dm: add infrastructure for DAX support dm thin: fix a race condition between discarding and provisioning a block dm btree: fix a bug in dm_btree_find_next_single() dm raid: fix random optimal_io_size for raid0 dm raid: address checkpatch.pl complaints dm: call PR reserve/unreserve on each underlying device sd: don't use the ALL_TG_PT bit for reservations dm: fix second blk_delay_queue() parameter to be in msec units not jiffies dm raid: change logical functions to actually return bool dm raid: use rdev_for_each in status dm raid: use rs->raid_disks to avoid memory leaks on free dm raid: support delta_disks for raid1, fix table output dm raid: enhance reshape check and factor out reshape setup dm raid: allow resize during recovery dm raid: fix rs_is_recovering() to allow for lvextend ...
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/device-mapper/dm-raid.txt58
1 files changed, 55 insertions, 3 deletions
diff --git a/Documentation/device-mapper/dm-raid.txt b/Documentation/device-mapper/dm-raid.txt
index df2d636b6088..e5b6497116f4 100644
--- a/Documentation/device-mapper/dm-raid.txt
+++ b/Documentation/device-mapper/dm-raid.txt
@@ -14,8 +14,12 @@ The target is named "raid" and it accepts the following parameters:
<#raid_devs> <metadata_dev0> <dev0> [.. <metadata_devN> <devN>]
<raid_type>:
+ raid0 RAID0 striping (no resilience)
raid1 RAID1 mirroring
- raid4 RAID4 dedicated parity disk
+ raid4 RAID4 with dedicated last parity disk
+ raid5_n RAID5 with dedicated last parity disk suporting takeover
+ Same as raid4
+ -Transitory layout
raid5_la RAID5 left asymmetric
- rotating parity 0 with data continuation
raid5_ra RAID5 right asymmetric
@@ -30,7 +34,19 @@ The target is named "raid" and it accepts the following parameters:
- rotating parity N (right-to-left) with data restart
raid6_nc RAID6 N continue
- rotating parity N (right-to-left) with data continuation
+ raid6_n_6 RAID6 with dedicate parity disks
+ - parity and Q-syndrome on the last 2 disks;
+ laylout for takeover from/to raid4/raid5_n
+ raid6_la_6 Same as "raid_la" plus dedicated last Q-syndrome disk
+ - layout for takeover from raid5_la from/to raid6
+ raid6_ra_6 Same as "raid5_ra" dedicated last Q-syndrome disk
+ - layout for takeover from raid5_ra from/to raid6
+ raid6_ls_6 Same as "raid5_ls" dedicated last Q-syndrome disk
+ - layout for takeover from raid5_ls from/to raid6
+ raid6_rs_6 Same as "raid5_rs" dedicated last Q-syndrome disk
+ - layout for takeover from raid5_rs from/to raid6
raid10 Various RAID10 inspired algorithms chosen by additional params
+ (see raid10_format and raid10_copies below)
- RAID10: Striped Mirrors (aka 'Striping on top of mirrors')
- RAID1E: Integrated Adjacent Stripe Mirroring
- RAID1E: Integrated Offset Stripe Mirroring
@@ -116,10 +132,41 @@ The target is named "raid" and it accepts the following parameters:
Here we see layouts closely akin to 'RAID1E - Integrated
Offset Stripe Mirroring'.
+ [delta_disks <N>]
+ The delta_disks option value (-251 < N < +251) triggers
+ device removal (negative value) or device addition (positive
+ value) to any reshape supporting raid levels 4/5/6 and 10.
+ RAID levels 4/5/6 allow for addition of devices (metadata
+ and data device tupel), raid10_near and raid10_offset only
+ allow for device addtion. raid10_far does not support any
+ reshaping at all.
+ A minimum of devices have to be kept to enforce resilience,
+ which is 3 devices for raid4/5 and 4 devices for raid6.
+
+ [data_offset <sectors>]
+ This option value defines the offset into each data device
+ where the data starts. This is used to provide out-of-place
+ reshaping space to avoid writing over data whilst
+ changing the layout of stripes, hence an interruption/crash
+ may happen at any time without the risk of losing data.
+ E.g. when adding devices to an existing raid set during
+ forward reshaping, the out-of-place space will be allocated
+ at the beginning of each raid device. The kernel raid4/5/6/10
+ MD personalities supporting such device addition will read the data from
+ the existing first stripes (those with smaller number of stripes)
+ starting at data_offset to fill up a new stripe with the larger
+ number of stripes, calculate the redundancy blocks (CRC/Q-syndrome)
+ and write that new stripe to offset 0. Same will be applied to all
+ N-1 other new stripes. This out-of-place scheme is used to change
+ the RAID type (i.e. the allocation algorithm) as well, e.g.
+ changing from raid5_ls to raid5_n.
+
<#raid_devs>: The number of devices composing the array.
Each device consists of two entries. The first is the device
containing the metadata (if any); the second is the one containing the
- data.
+ data. A Maximum of 64 metadata/data device entries are supported
+ up to target version 1.8.0.
+ 1.9.0 supports up to 253 which is enforced by the used MD kernel runtime.
If a drive has failed or is missing at creation time, a '-' can be
given for both the metadata and data drives for a given position.
@@ -207,7 +254,6 @@ include:
"recover"- Initiate/continue a recover process.
"check" - Initiate a check (i.e. a "scrub") of the array.
"repair" - Initiate a repair of the array.
- "reshape"- Currently unsupported (-EINVAL).
Discard Support
@@ -257,3 +303,9 @@ Version History
1.5.2 'mismatch_cnt' is zero unless [last_]sync_action is "check".
1.6.0 Add discard support (and devices_handle_discard_safely module param).
1.7.0 Add support for MD RAID0 mappings.
+1.8.0 Explictely check for compatible flags in the superblock metadata
+ and reject to start the raid set if any are set by a newer
+ target version, thus avoiding data corruption on a raid set
+ with a reshape in progress.
+1.9.0 Add support for RAID level takeover/reshape/region size
+ and set size reduction.