We are running about 12,000 accounts on two servers. We will be attempting to upgrade them to the latest 5.0.18, but trying to minimize restore times in the event of a failed upgrade.
One node which typically backs up in about 8hrs currently occupies about 400GB - this nodes runs everything. The other one, is much faster and with about half the storage, only takes 2 hours for backups. This node is an LDAP replica and runs everything except the logger.
Even though /opt/zimbra resides on a SAN, snapshots are not an option at this point due to license issues. I know I could take an LVM snapshot, but since I cannot quickly revert it back, it does us no good.
So, my question is, what changes on an upgrade? Other than the binary bits, do the stores get modified during the upgrade? DATA STORE, INDEX STORE, MESSAGE STORE ?