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Re: does btrfs have a feature?

On Thu, Aug 16, 2018 at 07:56:57AM +0200, Anders Andersson wrote:
> On Thu, Aug 16, 2018 at 3:47 AM, Zenaan Harkness <zenaan@freedbms.net> wrote:
> > Another correction below:
> >
> >> BTRFS also makes it extremely easy to expand an array if you add more
> >> disks, WITHOUT mucking around with LVM and md-raid. Just a simple
> >> command (something that ZFS cannot easily do at this time)
> >>
> >> btrfs device add /dev/sdX /path/to/array
> >> btrfs filesystem balance /path/to/array
> >
> >   “as simple as zpool add <pool name> <dev name>”
> >
> > >From here:
> >   http://list.zfsonlinux.org/pipermail/zfs-discuss/2018-August/031938.html
> >
> > Note that ZoL does not yet auto-rebalance (although there is at least
> > one script around to do it manually - copying files - and rebalance
> > can also be done manually with: zfs send ...; zfs receive ...
> I thought the problem was that you can't actually mix-and-match block
> devices of different sizes easily in ZFS, you need to plan ahead. I
> don't know the details because I've never used ZFS, but when I read
> about it I see a lot of warnings about striping and vdevs and whatnot.

If say you have a 3-drive RAID5, you can add extra drives (as above),
and also you can add an extra 3 drives as a separate 3-drive RAID
"unit" (vdev). Yes if you do the former, and the new drive(s) is/are
larger, the excess space will not be used by that ZFS vdev, but you
could also partition the spare space and use it as a separate vdev,
or for some other fs completely - plenty of options.

> With btrfs you can just throw any block devices together and it will
> automatically use whatever it can, restricted to the level of
> redundancy you requested.

Yes, something like that is my understanding too - BTRFS a little
"more fancy" in being able to use/stripe across extra space of new
drives - there's probably a wiki on it somewhere for the details...

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