Last sunday we have successfully upgraded our production Zimbra OSE from 5.0.22 to 6.0.10 on a Virtual Machine with Ubuntu 8.04 64 bit.
The upgrade was smooth. For safety we tested it before on another VM restored from backup.
The system manages about 70 mailboxes with a quite slow daily traffic (2000 messages/day) and 15 GB of store, and runs on a ESX 3.5 VM with 3GB of RAM and 2 CPU.
May be interesting for you to observe the change in the CPU usage trend grabbed from Virtual Center (see attached screenshot). The black square box is the upgrade time. It is interesting to note that now with 6.0 the CPU is always loaded at 25%, while with 5.0 it was more moderate.
Other minor glitch to report:
- automatic update check generates Java Null pointer exception (may be there is already some opened bugs)
- the image insertion in the signature has an erratic behaviour (errors with IE8); i'll file a bug for this
- the Flash statistics are working, but I prefer the previous RRD based
Anyway, really a good job, Zimbra people, thank you!