Plans for BTRFS in Fedora

Chris Adams cmadams at
Wed Feb 23 21:13:55 UTC 2011

Once upon a time, Matthew Garrett <mjg59 at> said:
> On Wed, Feb 23, 2011 at 02:08:08PM -0600, Chris Adams wrote:
> > Once upon a time, Matthew Garrett <mjg59 at> said:
> > > You can't move PVs.
> > 
> > What do you think pvmove does?
> Move PEs from one PV to another. You can't move a PV.

Not exactly; pvmove moves data from one PE to another (either in another
PV or in the same PV).  I guess I don't understand your original
objection though.  You can move data around within a PV (granted the
command usage to do this is non-obvious and it would be good for that to
improve, but it is also not a common use case) and from one PV to
another; what else is there to move?

> > > You need a separate /boot.
> > 
> > That's needed for more than just LVM (and probably won't go away, as it
> > is a lot simpler to handle a single method in the installer).
> Unless you're booting off iSCSI or really, really love software RAID 
> (which btrfs also kindly simplifies),

Using software RAID means "really, really love" it?  How else do you
propose to boot from software RAID (if you just kinda like it)?  We're
talking about the typical home/office desktop, so you aren't going to
have hardware RAID, and Linux software RAID is superior to motherboard
software RAID.

> the only reason you need a 
> separate /boot is because we're slow at putting updated filesystem 
> support in grub because there's no need because we default to a separate 
> /boot. There's a certain amount of circularity there.

Encrypted root filesystem requires a separate (non-encrypted) /boot, and
I think that's only going to increase in popularity (especially on
notebooks and other mobile devices).

> My experience with LVM is that any number of error states dump me into 
> an awkward recovery scenario.

I guess in the years I've used LVM, I haven't run into that "any number
of error states" (at least AFAIK, but since you didn't identify any of
them, it is hard to say).  Sure, when LVM was new, I had to learn a few
more commands to handle the "system didn't boot" case, but IIRC only
once was that related to LVM (and that was because I renamed a VG
without rebuilding the initrd, which may be no longer an issue with

If you don't know what you are doing, just "fsck" is going to be a
problem.  That's an issue with documentation and maybe making better
recovery tools, not LVM.  Adding a new set of commands to learn with
BTRFS isn't magically going to make it easier; you still have to learn
new stuff.

Chris Adams <cmadams at>
Systems and Network Administrator - HiWAAY Internet Services
I don't speak for anybody but myself - that's enough trouble.

More information about the devel mailing list