Re: [LSF/MM TOPIC] De-clustered RAID with MD

[Wols Lists <antlists@youngman.org.uk>]

On 29/01/18 21:50, NeilBrown wrote:
> By doing declustered parity you can sanely do raid6 on 100 drives, using
> a logical stripe size that is much smaller than 100.
> When recovering a single drive, the 10-groups-of-10 would put heavy load
> on 9 other drives, while the decluster approach puts light load on 99
> other drives.  No matter how clever md is at throttling recovery, I
> would still rather distribute the load so that md has an easier job.

Not offering to do it ... :-)

But that sounds a bit like linux raid-10. Could a simple approach be to
do something like "raid-6,11,100", ie raid-6 with 9 data chunks, two
parity, striped across 100 drives? Okay, it's not as good as the
decluster approach, but it would spread the stress of a rebuild across
20 drives, not 10. And probably be fairly easy to implement.

Cheers,
Wol