Re: Compression on Btrfs
On Sun, 2021-01-10 at 09:01 -0700, Chris Murphy wrote:
On Sun, Jan 10, 2021, 3:52 AM Patrick O'Callaghan
<pocallaghan(a)gmail.com>
wrote:
On Sat, 2021-01-09 at 18:01 -0700, Chris Murphy wrote:
> > > Does this mean that my VM image subvolume is being included in the
> > > compression? If that's the case I'll cease and desist.
> >
> > Did you set 'chattr +C' for nodatacow on the enclosing
> > directory/subvolume for the VM images? Nodatacow implies no
> > compression and no checksums.
>
> Probably but I don't remember. I've now set it just in case, but lsattr
> doesn't show it:
>
> $ sudo chattr +C /home/Windows
> $ lsattr -l /home/Windows
> /home/Windows/wimage ---
>
>
> Is this a bug or a feature?
>
If you're using libvirt, creating a new pool on Btrfs will automatically
set +C attribute.
It wasn't Btrfs at the time the image was created.
It's not possible to set this attribute once a file has data in
it, it's
not retroactive. You'll need to duplicate the file, in that same directory.
Because the directory has the attribute now, the duplicate will inherit the
attribute.
That's somewhat painful as the file is over 900GB and will need to be
copied to another drive and then back again, but thanks anyway.
poc