Re: [gentoo-amd64] Soliciting new RAID ideas

[Rich Freeman <rich0@gentoo.org>]

On Tue, May 27, 2014 at 7:38 PM,  <thegeezer@thegeezer.net> wrote:
> if you had lvm already you could
> simply 'move' then 'enlarge' your existing stuff (tm)

Yup - if you're not running btrfs/zfs you probably should be running
lvm.  One thing I would do is backup your lvm metadata when it changes
- I once got burned by an lvm error of some kind and an fsck scrambled
the living daylights out of my disk (an fsck on one ext3 partition
scrambled a different partition).  That is pretty rare though (but I
did find one or two mentions online of similar situations.

> : i'd like to know how
> btrfs would do the same for anyone who can let me know.

A btrfs filesystem pools storage.  You can add devices to the pool,
and remove devices to the pool.  If you remove a device with data on
it the data will get moved.  When adding devices btrfs does not
automatically shuffle data around - you can issue a balance command to
do so, but I wouldn't do this until you're done adding/removing
drives.

A nice thing about btrfs is that devices do not have to be of the same
size and it generally does the right thing.

The downside of btrfs right now for raid is that raid5/6 are still
very experimental.  They will support reshaping though, which is one
of the reasons I've stayed away from zfs.  Zfs also lets you
add/remove devices from a pool, but it does not allow you to reshape a
raid.

Rich