Also enhance possible takeover/reshape information and do some reformatting.
Signed-off-by: Heinz Mauelshagen <[email protected]> --- .../admin-guide/device-mapper/dm-raid.rst | 49 +++++++++++++++---- 1 file changed, 39 insertions(+), 10 deletions(-) diff --git a/Documentation/admin-guide/device-mapper/dm-raid.rst b/Documentation/admin-guide/device-mapper/dm-raid.rst index 3554c44414e63..e11f107647709 100644 --- a/Documentation/admin-guide/device-mapper/dm-raid.rst +++ b/Documentation/admin-guide/device-mapper/dm-raid.rst @@ -20,10 +20,10 @@ 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 supporting takeover + raid5_n RAID5 with dedicated last parity disk supporting takeover from/to raid1 Same as raid4 - - Transitory layout + - Transitory layout for takeover from/to raid1 raid5_la RAID5 left asymmetric - rotating parity 0 with data continuation @@ -48,8 +48,8 @@ The target is named "raid" and it accepts the following parameters:: raid6_n_6 RAID6 with dedicate parity disks - parity and Q-syndrome on the last 2 disks; - 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/to raid0/raid4/raid5_n + raid6_la_6 Same as "raid_la" plus dedicated last Q-syndrome disk supporting takeover from/to raid5 - layout for takeover from raid5_la from/to raid6 raid6_ra_6 Same as "raid5_ra" dedicated last Q-syndrome disk @@ -371,6 +371,7 @@ to safely enable discard support for RAID 4/5/6: 'devices_handle_discards_safely' + Takeover/Reshape Support ------------------------ The target natively supports these two types of MDRAID conversions: @@ -398,16 +399,44 @@ raid10 with near layout and even number of disks -> raid0 (select any in-sync de Reshape: linear: not possible raid0: not possible -raid1: change number of mirrors -raid4: add and remove stripes (minimum 3), change stripesize -raid5: add and remove stripes (minimum 3, special case 2 for raid1 takeover), change rotating parity algorithms, change stripesize -raid6: add and remove stripes (minimum 4), change rotating syndrome algorithms, change stripesize -raid10 near: add stripes (minimum 4), change stripesize, no stripe removal possible, change to offset layout +raid1: change number of mirrors +raid4: add and remove stripes (minimum 3), change stripesize +raid5: add and remove stripes (minimum 3, special case 2 for raid1 takeover), change rotating parity algorithms, change stripesize +raid6: add and remove stripes (minimum 4), change rotating syndrome algorithms, change stripesize +raid10 near: add stripes (minimum 4), change stripesize, no stripe removal possible, change to offset layout raid10 offset: add stripes, change stripesize, no stripe removal possible, change to near layout -raid10 far: not possible +raid10 far: not possible Table line examples: +### raid1 -> raid5 +# +# 2 devices limitation in raid1. +# raid5 personality is able to just map 2 like raid1. +# Reshape after takeover to change to full raid5 layout + + 0 1960886272 raid raid1 3 0 region_size 2048 2 /dev/dm-0 /dev/dm-1 /dev/dm-2 /dev/dm-3 + +# dm-0 and dm-2 are e.g. 4MiB large metadata devices, dm-1 and dm-3 have to be at least 1960886272 big. +# +# Table line to takeover to raid5 + + 0 1960886272 raid raid5 3 0 region_size 2048 2 /dev/dm-0 /dev/dm-1 /dev/dm-2 /dev/dm-3 + +# Add required out-of-place reshape space to the beginniong of the given 2 data devices, +# allocate another metadata/data device tuple with the same sizes for the parity space +# and zero the first 4K of the metadata device. +# +# Example table of the out-of-place reshape space addition for one data device, e.g. dm-1 + + 0 8192 linear 8:0 0 1960903888 # <- must be free space segment + 8192 1960886272 linear 8:0 0 2048 # previous data segment + +# Mapping table for e.g. raid5_rs reshape causing the size of the raid device to double-fold once the reshape finishes. +# Check the status output (e.g. "dmsetup status $RaidDev") for progess. + + 0 $((2 * 1960886272)) raid raid5 7 0 region_size 2048 data_offset 8192 delta_disk 1 2 /dev/dm-0 /dev/dm-1 /dev/dm-2 /dev/dm-3 + Version History --------------- -- 2.52.0
