RFC: Btrfs snapshots feature proposal for Fedora 13

RFC: Btrfs snapshots feature proposal for Fedora 13

[Chris Ball]

Hi,

I've written up a draft of an Fedora 13 feature proposal for
filesystem rollback using Btrfs snapshots that are automatically
created by yum:

   https://fedoraproject.org/wiki/Features/SystemRollbackWithBtrfs

It'd be great to get feedback on whether this is a good idea, and how
the UI interaction should work.  We're also discussing it in this
fedora-devel thread:

   http://thread.gmane.org/gmane.linux.redhat.fedora.devel/123695

Some comments I've got already received, from the thread:

* People want the UI to allow independent active snapshots per
  filesystem (i.e. btrfs /home is the live filesystem, and btrfs / is
  an older snapshot).

* Several people think that the ZFS Time Slider patches to nautilus=C2=B9
  look good, and want that for btrfs.  Sounds plausible, but I'm
  more interested in first working on ways to let developers feel
  comfortable upgrading to the development version of Fedora each
  day with the possibility of reverting.

* Instead of inventing a new system-config-blah, this should probably
  be part of Palimpsest=C2=B2.

* Perhaps we should encourage people using the Fedora installer with
  btrfs to create a rootfs separate to their /home, so that they can
  rollback rootfs snapshots without affecting their homedir.

Thanks!

- Chris.

=C2=B9:  http://blogs.sun.com/erwann/entry/zfs_on_the_desktop_zfs
    http://blogs.sun.com/erwann/entry/time_slider_screencast
    http://blogs.sun.com/erwann/entry/new_time_slider_features_in

=C2=B2:  http://library.gnome.org/users/palimpsest/stable/intro.html.en
--=20
Chris Ball   <cjb@laptop.org>
One Laptop Per Child
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Re: RFC: Btrfs snapshots feature proposal for Fedora 13

[Goffredo Baroncelli]

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On Tuesday 17 November 2009, Chris Ball wrote:
> Hi,
> 
> I've written up a draft of an Fedora 13 feature proposal for
> filesystem rollback using Btrfs snapshots that are automatically
> created by yum:
> 
>    https://fedoraproject.org/wiki/Features/SystemRollbackWithBtrfs
> 
> It'd be great to get feedback on whether this is a good idea, and how
> the UI interaction should work.  We're also discussing it in this
> fedora-devel thread:
> 
>    http://thread.gmane.org/gmane.linux.redhat.fedora.devel/123695
> 
> Some comments I've got already received, from the thread:
> 
> * People want the UI to allow independent active snapshots per
>   filesystem (i.e. btrfs /home is the live filesystem, and btrfs / is
>   an older snapshot).

On the basis of some empirical tests, I discovered that in btrfs a snapshot 
doesn't doens't affect the other subvolume(s). If / (root) and /home are 
different subvolumes, a snapshot of the / (root) doesn't affect the /home 
content, and viceversa. 

So if the root and the /home directory (or better the userS directories) are 
separate volumes, you have the required behavior.

> 
> * Several people think that the ZFS Time Slider patches to nautilus¹
>   look good, and want that for btrfs.  Sounds plausible, but I'm
>   more interested in first working on ways to let developers feel
>   comfortable upgrading to the development version of Fedora each
>   day with the possibility of reverting.
> 
> * Instead of inventing a new system-config-blah, this should probably
>   be part of Palimpsest².
> 
> * Perhaps we should encourage people using the Fedora installer with
>   btrfs to create a rootfs separate to their /home, so that they can
>   rollback rootfs snapshots without affecting their homedir.

On the basis of my tests, I think that is sufficient to create a volume for 
the root ('/') and on for the /home (or a specific subvolume for every user). 
Then it is possible to snapshot and "time sliding" every subvolume without 
affecting the others.

I would like to add a my comment: in btrfs I think that "snapshot" (for the 
btrfs snapshot) is not the best name. I think that a better term is "branch". 

For example the btrfs snapshot capability may be used not only for recovering 
from a mistake, but also may be used for maintaining different 
configurations...

> Thanks!
> 
> - Chris.

BR
G.Baroncelli
> 
> ¹:  http://blogs.sun.com/erwann/entry/zfs_on_the_desktop_zfs
>     http://blogs.sun.com/erwann/entry/time_slider_screencast
>     http://blogs.sun.com/erwann/entry/new_time_slider_features_in
> 
> ²:  http://library.gnome.org/users/palimpsest/stable/intro.html.en
> -- 
> Chris Ball   <cjb@laptop.org>
> One Laptop Per Child
> --
> To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> 


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