[Discuss] btrfs

[Edward Ned Harvey (blu)]

> From: Dan Ritter [mailto:dsr at randomstring.org]
> 
> > In btrfs and zfs, it goes like this:
> > mirror dev0 dev1 dev2
> > or
> > raid1 dev0 dev1 dev2
> > This makes a 3-way mirror.  Total usable capacity of a single disk, triple
> redundant.
> 
> This is incorrect for btrfs. Assuming 3 identical devices, btrfs
> raid1 creates a 2-way replication with a capacity of 1.5x a
> single device.

Ahh.  Thanks for that clarification.  So in btrfs, raid1 means something similar to raid-1e.  Whereas, in zfs, raidz is something similar to raid-1e.
So in reality, the btrfs raid1, and the zfs raidz both have the characteristics:

1 disk of redundancy
performance should be approx N-1 disks times a single disk
Incrementally expandable by adding individual disks?  I know raidz is not.