On Sun, 13 Feb 2011 17:30:59 +0000, Hugo Mills wrote:

quoted

First: In the / filesystem I create a subvolume named /home. As soon as
the subvolume is created, I can already see the entry point in /home
without having to mount it separately. Is that expected?

   Yes.

What happens if I mount the home subvolume into a different point, like:

mount -o subvol=home /home2

and then change a file in /home (which is accessible through the default
subvolume)?

Will the change be reflected on both mount points? Or the inverse
(change /home2)?

quoted

So, which is best? Looks like mounting subvolumes is not necessary.

   I would recommend putting nothing in the root of the filesystem
*except* subvolumes. i.e. create a "root" subvolume in / that contains
your root filesystem, and make that the default. Then you can mount
your btrfs root subvolume (i.e. the thing that contains all the other
subvolumes) somewhere like /media/btrfs-root, for purposes of managing
subvolumes.

So you would recommend creating both /root and /home subvolumes, to be
mounted separately, or create /root and /root/home subvolumes?

quoted

like to use nodatasum except for /home, will the following work?

mount -o nodatasum /dev/x /
btrfs subvolume create /home
mount -o datasum,subvol=home /dev/x

   I'd expect that to work, although I haven't tried it myself.

What if I remount the /home subvol into /home2. What happens when I
touch a file through /home (nodatasum) and what happens when I use
/home2 - since both are available at the same time?