Re: Btrfs and raid5 status with kernel 3.14, documentation, and howto

[Marc MERLIN <marc@merlins.org>]

On Tue, Mar 25, 2014 at 01:11:43AM +0000, Martin wrote:
> Yes, looking good, but for my usage I need the option to run ok with a
> failed drive. So, that's one to keep a development eye on for continued
> progress...
 
So it does run with a failed drive, it'll just fill the logs with write
errors, but continue working ok.
 
> There's a big thread a short while ago about using parity across
> n-devices where the parity is spread such that you can have 1, 2, and up
> to 6 redundant devices. Well beyond just raid5 and raid6:
> 
> http://lwn.net/Articles/579034/
 
Aah, ok. I didn't understand you meant that. I know nothing about that, but
to be honest, raid6 feels like it's enough for me :)

> btrfs raid1 at present is always just the two copies of data spread
> across whatever number of disks you have. A more flexible arrangement is
> to be able to set to have say 3 copies of data and use say 4 disks.
> There's a new naming scheme proposed somewhere that enumerates all the
> permutations possible for numbers of devices, copies and parity that
> btrfs can support. For me, that is a 'killer' feature beyond what can be
> done with md-raid for example.
 
Right. That's on the roadmap from what I read here, just not ready yet.

Marc
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