It starts getting exponentially more expensive the closer you get to 100% uptime.

Consider security upgrades. Even with linux, you may need to reboot the server (upgrading the kernel for instance), or at least restart a service which can cause a few minutes downtime.

That said, there's no reason a site should have to go down two times a week for regular maintenance, so I do think there is a lot of room to improve.

The main things to consider:

a. Are your services monitored 24x7 automatically? This is a must. If something crashes (apache, mysql, etc), it should be automatically detected and restarted to minimize any downtime. If it can't be restarted, a tech should be paged.

b. Is your O/S and the apps on the O/S managed? This is also a must. In the last six months there have been major holes in PHP, Apache, Sendmail, BIND, and even the linux kernel itself.

I hope you find this helpful. And yes, GossamerHost dedicated servers include both of these, and keeps a really good uptime to boot. If you have any questions about it, please feel free to contact me.

Cheers,

Alex
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Gossamer Threads Inc.