Re: [PATCH 2/2] dm-raid: Fix minimal_devs for raid6

[Heinz Mauelshagen <heinzm@redhat.com>]

NACK

4 devs is actually the mandatory minimum for raid6;
minimum of 2 data stripes plus 2 devices for parity and q-syndrome.

FWIW: the 2 devices minimum for the raid4/5 layouts are correct too,
            because those personalities are able to drive 2 devices as raid1
            (i.e. allow for takeover from raid1 with 2 legs)
            in order to reshape them to 'real' raid4/5 by adding N>0 devices

Heinz

On 10/28/2015 07:50 PM, Andy Grover wrote:
> A raid6 device can be created from 3 devs. This previously didn't cause
> an error because minimal_devs was not being checked.
>
> Signed-off-by: Andy Grover <agrover@redhat.com>
> ---
>   drivers/md/dm-raid.c | 6 +++---
>   1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/md/dm-raid.c b/drivers/md/dm-raid.c
> index 5941cfd..1ded052 100644
> --- a/drivers/md/dm-raid.c
> +++ b/drivers/md/dm-raid.c
> @@ -90,9 +90,9 @@ static struct raid_type {
>   	{"raid5_ra", "RAID5 (right asymmetric)",	1, 2, 5, ALGORITHM_RIGHT_ASYMMETRIC},
>   	{"raid5_ls", "RAID5 (left symmetric)",		1, 2, 5, ALGORITHM_LEFT_SYMMETRIC},
>   	{"raid5_rs", "RAID5 (right symmetric)",		1, 2, 5, ALGORITHM_RIGHT_SYMMETRIC},
> -	{"raid6_zr", "RAID6 (zero restart)",		2, 4, 6, ALGORITHM_ROTATING_ZERO_RESTART},
> -	{"raid6_nr", "RAID6 (N restart)",		2, 4, 6, ALGORITHM_ROTATING_N_RESTART},
> -	{"raid6_nc", "RAID6 (N continue)",		2, 4, 6, ALGORITHM_ROTATING_N_CONTINUE}
> +	{"raid6_zr", "RAID6 (zero restart)",		2, 3, 6, ALGORITHM_ROTATING_ZERO_RESTART},
> +	{"raid6_nr", "RAID6 (N restart)",		2, 3, 6, ALGORITHM_ROTATING_N_RESTART},
> +	{"raid6_nc", "RAID6 (N continue)",		2, 3, 6, ALGORITHM_ROTATING_N_CONTINUE}
>   };
>   
>   static char *raid10_md_layout_to_format(int layout)