Re: [sqlite] Multi-master replication with updated Versioning?extension

On 30 Jul 2009, at 6:19pm, Jay A. Kreibich wrote:

> You're not really supposed to
>  dump and restore a multi-master system.

We're back to talking about synchronising different copies of the  
database again, aren't we ?

Dumping and restoring a multi-master system means restoring the entire  
context of all the copies of the database.  You have to not only  
restore the contents of one copy of the database, but also restore the  
state of all other copies.  And if you're using a journaling method to  
manage your synchrony, restore the state of all the journals too.

The only exception to this is if the dump was done when all sites  
agreed that they all had completely synchronised up-to-date copies of  
the database.  And many multi-master databases are never in that  
state.  So the question is 'what was dumped, and what state was it in' ?

So the next question is how your journaling system was designed.  You  
can design a journaling and synchronising system so that any site(s)  
can restore from a backup at any time, and the next time everyone  
synchronises they'll get their best data.  But often this is not  
considered when the system is designed and the system loses data or  
worse still corrupts everyone else's.

Simon.
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