[Box Backup] Backup the backup

[Chris Wilson]

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Hi Simon,

On Wed, 1 Nov 2006, [ISO-8859-1] Simon Lundstr=F6m wrote:

>>  I'm talking about a way to recover from a fatal and prolonged crash of =
the=20
>>  local backup store (bbstored) by switching to an offsite mirror of the=
=20
>>  store, which is readable and writable to the client, until the local st=
ore=20
>>  can be repaired (at which point I assume that you would change back to=
=20
>>  using the local one).
>
> Not really what I want, but kind of.
>
> I want an way to have two (or more) backup server that are in sync (sort =
of).=20
> The client can use the local backup store located on the company LAN when=
=20
> they are on the company LAN. Also I want the ability to choose another=20
> secondary backup store that is available from the Internet when they are=
=20
> travelling or otherwise not on the company LAN.

This is very difficult. Whenever the client is using the remote server,=20
the local server is more up-to-date than the local one. rsync will not=20
realise this and will happily overwrite the new data with old. If you try=
=20
to do an incomplete sync, for example telling rsync not to overwrite newer=
=20
files on the secondary server, you will end up with a mess on the remote=20
server.

I can't think of a way to make this work reliably with existing tools. The=
=20
only possibility is some very complicated two-way sync mechanism or=20
replicating filesystem between the local and remote servers. I would=20
certainly hesitate to do something so experimental as a primary backup=20
solution, and I would test it very heavily.

Why not have the client back up to the local server even when it's on the=
=20
road? You should have plenty of download bandwidth on those sites (more=20
than the client has upload bandwidth) and it avoids this problem=20
completely.

Cheers, Chris.
--=20
_ ___ __     _
  / __/ / ,__(_)_  | Chris Wilson <0000 at qwirx.com> - Cambs UK |
/ (_/ ,\/ _/ /_ \ | Security/C/C++/Java/Perl/SQL/HTML Developer |
\ _/_/_/_//_/___/ | We are GNU-free your mind-and your software |

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