We deployed our new Linux/Exim/Spamassassin mail server on Friday (always a good idea to deploy the day before a long weekend when no admins are around). The load has been hovering around 1.3 on the 15-minute average.
The machine is responsive, and mails are delivered in reasonable time. Can we assume that this is acceptable?
How is a certain amount of load deemed acceptable or not acceptable? What metrics are used?
Best Answer
Basic rule of thumb: if the system is responsive, if it's working in a timely fashion, then you're fine.
Loads below two aren't much of a worry. I've had systems hit four or five and still work fine, although that would be an indicator that there's a lot of queuing issues with the network or drives (I/O issues can cause high loads even though the system is very responsive).
Check your mail queue lengths periodically and the logs for undeliverable issues and problems of that nature. If the delivery queue stays relatively low that's fine.
You can much around with getting disk averages and network I/O information but if you're not seeing delivery issues (I sent the message fifteen minutes ago and it hasn't arrived yet!) and you can work on the system via console (or ssh) without a lot of latency, you should be fine.