User space RAID-6 access

User space RAID-6 access

> test_stripe assumes that the data starts at the start of each device.
> AS you are using 1.2 metadata (the default), data starts about 1M in to
> the device (I think - you can check with --examine)
>
> You could fix test_stripe to put the right value in the 'offsets' array,
> or you could create the array with 1.0 or 0.90 metadata.

Hi Neil,

thanks for the info, maybe this should be a second patch.

In the meantime, please find attached a patch to restripe.c
of mdadm 3.2 (latest, I hope).

This should add the functionality to detect, in RAID-6,
which of the disks potentially has problems, in case of
parity errors.

Some checks take place in order to avoid false positives,
I hope these are correct and enough.

I'm not 100% happy of the interface (too much redundancy),
but for the time being it could be OK.

Of course, any improvement is welcome.

Please consider to include these changes to the next mdadm
whatever release.

bye,

Signed-off-by: NeilBrown <neilb@suse.de>