I use Drive Genius. Have had drives crater in the past. This monitors drives in the background and lets you know when they need attention before it gets too late. It also lets me know when they can be optimized defragging them. Which has only been needed on a backup drive that gets a lot of large mail stores. And yes despite the OS, the others still get fragmented but not enough to worry about. Using Drive Genius more of a preventative thing though and never actually needed it for the last 4 years. Just have it for peice of mind because it is much easier to fix things before they actually break.
Used to use other stuff but just haven't needed it.
Run my own Kerio mail server and use hosted Canit for anti-virus/anti-spam for the server accounts and have been amazed. Maybe one or two spams a month, and same for false positives. No need for anything else on email clients. Host email and web sites at
ZipBang.Com - Email Hosting Service.
Best thing to do is keep backups! Best backup is use two external drives one for time machine and the other for bootable backups using something like Carbon Copy Cloner. Apple's time machine wireless routers while convenient for wireless backup of laptops seem to die after a year or so, Very inconvenient. Replace my Mac Mini servers every few years and use an old one to run Server and set it up with an external drive for a network Time Machine server. Do the same thing with another mac mini and have an external drive for bootable backup of each machine on my network so if something goes horribly wrong can just plug in the corresponding external drive and go.