VPS etiquette, and how server resources are meant to be used

Question

I'm renting a tiny Linode to mess around with, host my site and learn more about Linux. It's a VPS with 512MB of RAM and 16GB of storage.

I've never owned a computer that wasn't sitting in front of me before, so I've got some questions:

• I've got Apache and MySQL running. Do I need to leave a certain amount of memory free?

               total       used       free     shared    buffers     cached
  Mem:           498        382        116          0         41        185
  -/+ buffers/cache:        154        343
  Swap:          255         13        242
  

• What kind of CPU usage would you call excessive?

  Graph: http://i.stack.imgur.com/O60J6.png

I know if this was my laptop, it'd be odd to have the CPU running at 100% constantly and 95% of memory in use. Does the same apply here?

And I know I'm nowhere near there yet, but... at what point would you buy, for example, a dedicated DB server? How do I know when this server doesn't cut it anymore?

Answer 1

• For the RAM: with what you're running, your free RAM is more than enough. After buffers and cache, you're still just at 30% utilization. (The key thing is the free column in the +/- buffers/cache row)
• For the CPU: Again, you're in the clear at 1% average. If it starts spiking to 100% regularly, then you have some capacity or code issues.

As far as when you need to upgrade/expand: When your site gets slow, just figure out the bottleneck and move on from there. At this point, you're so underutilized that it's not even on your radar.