[Dovecot] [ Re: best practises for mail systems]
andrei.michescu at miau.ca
Wed Jun 6 18:22:05 EEST 2012
> But the replication between "points of presence" (5 big datacenters, one
> per continent, won't be good topology) will be painful and we easily
> face split-brain situation, whichever replication scheme I can imagine.
The split-brain is indeed the biggest problem of common replication
schema. But IMAP was designed to work in disconnected mode most of the
time and have only quick synchronizations.
So by design IMAP standard works in master-master models.
Getting back to the above picture (catastrophic failure of all the
transcontinental links): one synchronizes his laptop in Europe (EU),
crosses the ocean to North America (NA) and synchronizes again his laptop.
In this moment all the changes on the EU hub up to the point of last
synchronization are merged into the NA hub. This is the beauty of IMAP.
The biggest challenge on the the above scenario is the post-catastrophic
synchronization which would move huge amounts of data across the links.
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