[Box Backup] Backup the backup

[Ben Summers]

On 1 Nov 2006, at 11:51, Simon Lundstr=F6m wrote:

>
> On Nov 1, 2006, at 10:13 AM, Chris Wilson wrote:
>
>> This is very difficult. Whenever the client is using the remote =20
>> server, the local server is more up-to-date than the local one. =20
>> rsync will not realise this and will happily overwrite the new =20
>> data with old. If you try to do an incomplete sync, for example =20
>> telling rsync not to overwrite newer files on the secondary =20
>> server, you will end up with a mess on the remote server.
>
> =46rom man rsync:
> -u, --update                update only (don't overwrite newer files)
>
> I thought that was going to work, but maybe not?

No. That'll mean the rsyncing computer won't send it's directories =20
properly after an update.

>
>> I can't think of a way to make this work reliably with existing =20
>> tools. The only possibility is some very complicated two-way sync =20
>> mechanism or replicating filesystem between the local and remote =20
>> servers. I would certainly hesitate to do something so =20
>> experimental as a primary backup solution, and I would test it =20
>> very heavily.
>
> Maybe unison http://en.wikipedia.org/wiki/Unison_%=20
> 28file_synchronizer%29 is the way to go?

No. Two way sync will corrupt the store.

>
>> Why not have the client back up to the local server even when it's =20=

>> on the road? You should have plenty of download bandwidth on those =20=

>> sites (more than the client has upload bandwidth) and it avoids =20
>> this problem completely.
>
> Because many of these companies are small and don't have a lot of =20
> bandwidth since they only surf and check their mail they can't only =20=

> use remote backup but needs local backup. (5-10 ppl transmitting =20
> 2-10GB over 2Mbit can be come quite slow. I will only use lazy =20
> mode, i.e. backups will not be automatic. Besides not all clients =20
> can have servers or ports opened in their firewall.

I'm not convinced you're going to get the current system to do what =20
you want. I think you need servers to co-operate with each other =20
before this setup will be happy.

Ben