What size VPS plan (RAM) will I need for these sites?
I currently have 3 websites I am considering moving to a VPS plan from shared hosting.
My main site comprises a wordpress blog and a vbulletin forum. This site has around 183,000 page views, and 25,801 Absolute Unique Visitors a month, and the forum has an average of around 70 visitors online at a time, sometimes more. It is getting slow on asmallorange.com shared, hence the desire to move to a managed VPS.
The other main site has around 45,000 uniques a month but is less server intensive as it is only a store and a wordpress blog.
I really want to increase traffic for both sites this year, so I'm looking for a VPS with room to grow.
I'm not sure if 512 ram will be enough (mostly thinking about the forum I guess), and would love some advice.
512MB is a huge amount and ample if you know how to get the most out of it. Unfortunately the software you choose to run probably isn't making the most of it, so getting it running smoothly might not be possible.
You can always try it, but I would budget for a larger system and make sure your VPS provider can handle the upgrade so if you do find that 512MB isn't enough you can switch within hours rather than days.
Just as a really rough outline...
MySQL : 80MB
Finely tuned Apache : 1.5MB per concurrent connection
Typical Apache : 15MB per concurrent connection
I'm not sure about vbulletin or wordpress, it depends how they are run.
The more you have free after all the concurrent connections (and remember each HTTP connection typically lasts 15 seconds so they build up really quickly) the better the database will perform. If you use lighttpd instead of Apache you will be considerably better off.
Blue Room Hosting - High availability UK VPS KVM Plans - Multiple OS support. Virtual console and CD drive.
I think 512 would probably be fine. Many VPS Providers can change your memory almost instantly so I would make sure that they offer the upgrade option if needed. Also some offer a certain amount of gauranteed Memory and more Burstable. With this type of config your site will still handle it if you run out of memory and you will have time to upgrade to more with downtime.