Question: Yesterday I rebooted the web server machine, but I'm trying to figure out why the graph below shows prior rebooting the memory almost full of cache and just a bit of active memory used. Would there be any problem keeping it the same was it was or rebooting every ~30 days is what I'm suppose to do?

Thanks

<http://img513.imageshack.us/i/localhostlocaldomainmem.png/>

Answer: 
Check out [this blog post](http://egloo.wordpress.com/2008/10/29/linux-cached-memory/), it might shed some light on the issue.
Linux likes to use all otherwise-unused memory for disk cache. There's no performance downside, and there just might be a benefit because the disk won't need to be touched for some disk reads.