I have a server that's recently started to freeze on an increasingly frequent basis. The box is still powered up but Zimbra services are not accessible, and more importantly, all SSH connections are being refused. This is a complicating factor as I'm in Dubai and the box is hosted 3,500 miles away in the UK and it requires "phone a friend" to power cycle the box and restore access, which can take 8-12 hours. Meanwhile I get "mails not working, can you give me a call" text messages from the small number of family and friends the server is hosting mail for.
I have no idea what is causing this. I'm at the moderately competent level of someone capable of hacking about to get stuff like Zimbra and VMware installed and working (the box also hosts a VM for a Symantec mail security appliance) but I am not an experienced Linux admin and I don't have strong knowledge of troubleshooting. With my limited knowledge I've been looking at the Zimbra logs (which show nothing) and /var/log/messages which also shows nothing - I think the logger processes are being frozen along with everything else when the box stops responding so there's no record of what's happening.
Recently the box has moved to 5.0.6 where a couple of lock-ups occurred, followed by a 'yum update', a brief move to 5.0.7 and then to 5.0.8 where several freezes have occurred in rapid succession. Again, I'm not 100% certain this is anything to do with Zimbra, or the real correlation of events, but the frequency of problems is increasing.
Your thoughts and any guidance on how to figure out what may be happening would be greatly appreciated!