some project ideas: NFS4 ACLs, resilience on the same device, allowing to specify which devices are "distinct" in a RAID

[Christoph Anton Mitterer <calestyo@scientia.net>]

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Hi.

Christian Kujau suggested in the wiki[] to post project ideas to the
list to give them some possible wider discussion.

So far I've had these ideas:

1) NFS 4 ACLs[1]
Not sure whether it has been proposed and/or rejected before),... but it
would be nice if it was a goal for btrfs to support NFS4 ACLs.

These are much more powerful than POSIX.1e ACLs... and I think it would
be nice if all the major Linux filesystems would support them in
addition or as an alternative to the POSIX.1e ACLs. Of course one would
have to think about a schema what happens when there are ACLs of both
types in place for a file, whether this is allowed at all or not and how
rules would be merged.


2) DUP of data
I think btrfs already supports to have the same blocks copied on
multiple locations on the same device for resilience,... but only for
meta-data...
I think ZFS supports that for data as well...
Advanced code could try to spread such replicas as far as possible (i.e.
different spindles on rotating drives, ... different chips on flash
based storage)


3) allow to tell btrfs which devices are really distinct in a RAID
For some reasons people may have setups e.g. like this:
/dev/sda1
/dev/sda2
/dev/sdb1
/dev/sdc1
Now one could create a RAID5 on them, but apparently sda1 and sda2 are
on the same disk... so I'd like a way to tell btrfs that these are the
"same" and not really that redundant.


Cheers,
Chris.

[0] https://btrfs.wiki.kernel.org/index.php?title=Talk%3AProject_ideas&action=historysubmit&diff=26841&oldid=26831
[1] https://btrfs.wiki.kernel.org/index.php/Talk:Project_ideas#NFS4_ACLS

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