So I'm not looking for a distributed cluster - simply a splitting of designated functions. Clients would only be connecting to the primary server. I know Dovecot supports an alternate storage location - that's what made me think this was possible. What I'm more uncertain of is Solr.

My (probably flawed) thinking is to take advantage of a low-cost high-availability cloud server to provide primary email services. Dovecot, Postfix, and even ASSP don't have significant memory or processor requirements by themselves - especially for my smaller user base. However - storage in the cloud can be at a premium. Therefore I'm thinking of continuing to self-host the archives. And my own server has the raw power & memory to handle Solr easily. What's triggering this is our ISP's quality has been deteriorating - and the alternates don't appear much better.

Initial visualization would have a VPN/SSH connection between the servers, and NFS mounting my storage to the cloud server for archives. If our connection drops - in theory "current" mail handling is unaffected.

1. If Dovecot is unable to reach the remote Solr - upon re-connection will Solr be told about the new messages to index? Or do I need to setup a periodic re-scan?

2. Is there a "better" method of accessing the archive storage area than NFS? Either a different network file system or is there a way to do it with Dovecot directly?