Synchronizing xs-0.3 and xo-??? --- backups

[Tomeu Vizoso]

On Tue, Apr 22, 2008 at 6:46 AM, Martin Langhoff
<martin.langhoff at gmail.com> wrote:
> Hi Michael,
>
>  thanks for looking into this - I had the wikipage in my sight, but not
>  the bugs you listed. Excellent, reading up to fill the gaps.
>
>
>  >  Based on feedback from Peru, Mexico, and Nepal, the "restoration from
>  >  disaster-recovery backups" XO/XS coordination feature has been steadily
>  >  rising in priority. I also notice that "Backups" is your first line-item
>  >  on the XS-0.3 roadmap.
>
>  Yes. I was planning on looking at it next week, but happy to bump it up.
>
>
>  >  My large question is: "what changes need to be made to the XO's OS,
>  >  (currently to candidate-703) in order to make progress in this feature
>  >  cluster?"
>
>  I was hoping to say "here's a Python script that needs to be added to
>  the image and called opportunistically when NM tells us we are
>  connected to the XS (and at a regular interval during that situation)
>  and we have plenty battery or a powercord".
>
>
>  >  Sub-questions:
>  >
>  >   * What backup scheme do we actually intend to deploy? (Current choices appear
>  >    to be Wad's "dumb-rsync" method [1] and Ivan's method [2].
>
>  Wad's too simple, I am hoping to use a slightly simplified version of
>  Ivan's. For the restore part, I think I will drastically simplify
>  things from Ivan's approach.
>
>
>  >   * Does the chosen scheme permit us to sanely combine old backups with
>  >    an XO build that makes breaking changes to file layouts?
>
>  O-o-ouch! I imagine you are thinking about datastore overhaul insurance...? ;-)

Yes, when Ivan designed his backup scheme, he had in mind a future
rewrite of the DS, using an incompatible data backend.

>  Yes and no. My target layer is purely files, and we use rsync to copy
>  them over either way. *If* the datastore changes, and file layouts
>  change significantly, we'll copy that verbatim to the XS. If (for
>  restore purposes) the XO wants to read data from before the datastore
>  change, it will have to know how to... we'll just provide the old
>  files ;-)
>
>  ... though the XS could provide translation services to help make that
>  easier. In practice, if the datastore stuff is today in a library on
>  the XO, it will be kept to support legacy data...?

The DS is today a dbus service, but a python module that access the
data in the old format wouldn't be hard to provide.

>  (Was going to say that any datastore change must support the fact that
>  data will be on "old" USB sticks, but the Journal saves in a different
>  format to the USB stick.)

We have plans to stop using usb sticks and sd cards as extensions of
the local DS, and just display the files on it.

Do we have a set of requirements for the next releases? Robson is
interested in working on restoring and sharing of individual journal
entries from the server, what priority have these use cases?

Thanks,

Tomeu