Re: Copying a btrfs filesystem from one host to another, reflinks, compression

[Nicholas D Steeves <sten@debian.org>]

Hi Andy,

On Wed, 4 Dec 2024, 23:26 Andy Smith, <andy@strugglers.net> wrote:

> On Thu, Dec 05, 2024 at 07:11:59AM +0300, Andrei Borzenkov wrote:
> > 05.12.2024 01:24, Andy Smith wrote:
> > > rsync or tar | ssh | tar are not going to handle reflinked files,
> > > are they?
> > >
> > > Should I be using btrfs-send?
> >
> > btrfs send/receive has better support for sharing data between files,
> yes.
> > It is not guaranteed, that destination will have exactly the same data
> > layout though; btrfs send may decide to send full data instead of sending
> > clone request. I am not sure about exact conditions, IIRC one requirement
> > for cloning is proper alignment.
>
> Hmm. I don't mind if the destination has a  bit of a different layout
> but I would not like if a significant number of the regions on the
> source got deduplicated…
>
> I guess I will have to try it and see what happens (time-consuming,
> given the size).
>
> If it expands too much
> > > Source host's kernel is 5.10.0-32; btrfs-progs v5.10.1 (Debian 11).
> > > Destination would be Debian 12 so kernel 6.1.0-28 and btrfs-progs v6.2
> > >
> >
> > According to man btrfs-send, --compressed-data should preserve
> compression.
>
> Looks like I would have to install a newer btrfs-progs on the sender as
> I read in:
>

https://backports.debian.org/Instructions/

You can use bullseye-backports on the sender to install a 6.x kernel and
btrfs-progs versions from bookworm (Debian 12).

Whether it works or not, please consider writing to the backports mailing
list, and maybe CC Alexander Writ, because you have a compelling use case
for keeping at least a subset of oldstable backports active longer than
they're usually kept active.

I hope these backports save you some time!
Regards,
Nicholas