diff options
Diffstat (limited to 'Documentation/device-mapper/dm-raid.txt')
| -rw-r--r-- | Documentation/device-mapper/dm-raid.txt | 31 |
1 files changed, 26 insertions, 5 deletions
diff --git a/Documentation/device-mapper/dm-raid.txt b/Documentation/device-mapper/dm-raid.txt index c75b64a85859..cd2cb2fc85ea 100644 --- a/Documentation/device-mapper/dm-raid.txt +++ b/Documentation/device-mapper/dm-raid.txt @@ -17,7 +17,7 @@ The target is named "raid" and it accepts the following parameters: raid0 RAID0 striping (no resilience) raid1 RAID1 mirroring raid4 RAID4 with dedicated last parity disk - raid5_n RAID5 with dedicated last parity disk suporting takeover + raid5_n RAID5 with dedicated last parity disk supporting takeover Same as raid4 -Transitory layout raid5_la RAID5 left asymmetric @@ -36,7 +36,7 @@ The target is named "raid" and it accepts the following parameters: - 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 + layout 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 @@ -137,8 +137,8 @@ The target is named "raid" and it accepts the following parameters: 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 + and data device tuple), raid10_near and raid10_offset only + allow for device addition. 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. @@ -161,6 +161,15 @@ The target is named "raid" and it accepts the following parameters: the RAID type (i.e. the allocation algorithm) as well, e.g. changing from raid5_ls to raid5_n. + [journal_dev <dev>] + This option adds a journal device to raid4/5/6 raid sets and + uses it to close the 'write hole' caused by the non-atomic updates + to the component devices which can cause data loss during recovery. + The journal device is used as writethrough thus causing writes to + be throttled versus non-journaled raid4/5/6 sets. + Takeover/reshape is not possible with a raid4/5/6 journal device; + it has to be deconfigured before requesting these. + <#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 @@ -242,6 +251,13 @@ recovery. Here is a fuller description of the individual fields: in RAID1/10 or wrong parity values found in RAID4/5/6. This value is valid only after a "check" of the array is performed. A healthy array has a 'mismatch_cnt' of 0. + <data_offset> The current data offset to the start of the user data on + each component device of a raid set (see the respective + raid parameter to support out-of-place reshaping). + <journal_char> 'A' - active raid4/5/6 journal device. + 'D' - dead journal device. + '-' - no journal device. + Message Interface ----------------- @@ -303,10 +319,15 @@ 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 +1.8.0 Explicitly 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. 1.9.1 Fix activation of existing RAID 4/10 mapped devices +1.9.2 Don't emit '- -' on the status table line in case the constructor + fails reading a superblock. Correctly emit 'maj:min1 maj:min2' and + 'D' on the status line. If '- -' is passed into the constructor, emit + '- -' on the table line and '-' as the status line health character. +1.10.0 Add support for raid4/5/6 journal device |