I've been with Linode for about 4 years now and I'm slowly starting a small hosting business. Currently I host 6 domains (with about 15 vhosts, these are mostly off my site) and get roughly 1500 unique visitors per day.

I know I'm nowhere close to needing to expand at the moment, but hopefully I'll need to at some point. My CPU graphs are mostly idle (~1-3% except during backups and the like), IO graphs are low also (~150 Average IO Rate).

What are some early indicators of when you need to expand and what are the recommended ways of expanding? A obvious factor is page load times. Preferably I'd like some other indicates (such as CPU Usage, IO Rate, and Network Usage) of when a 360 can't provide superb load times and performance to my users/customers. I'm not expecting an "once you get x views per day" type of answer since I know there are a lot of contributing factors (static vs dynamic pages just to name one).

I'm currently running a single 360 (Ubuntu 9.04). I think when the time comes I'll be looking at getting a second 360 (at the same DC) and splitting MySQL, Apache2, and my Mail Server up. Are there any advantages of getting a 720 over a second 360? How would you personally accommodate a growing Webserver (serving mostly dynamic pages), MySQL Server, and Email Server (Postfix/Courier-IMAPd)?

Changing services and operating systems is always a possibility to squeeze more power out of my Linode. I've heard good things about LightHTTPd, nginx, PostgreSQL, and Dovecot. A lot of people also seem to be using CentOS. I've already made a few basic tweaks (Apache MaxClients/KeepAlive) and haven't noticed a difference (not that I expected to with how low my usage is).

Thank you for your time,
Smark

I'd be mainly concerned with Swap usage. Once you start using over say 10MB swap, you should try to see if there's any tweaking that needs to be done. Once you start using over 100MB swap, you will probably start seeing performance problems.

I used to think the used swap size by itself was a performance indicator, until munin graphs showed my site having swap size of ~200M without very little *use* of the swap. I had not seen this in years past. If the swap space has very little I/O traffic (once filled) the volume of swap by itself probably does not indicate a problem in my opinion.

James

Linux will, all by itself, swap rarely-used stuff. It does this to free up RAM for cache.

The logic is, the memory isn't being used, so better to swap it out and put it towards something useful.

Apart from possible reliability concerns, I wouldn't bother getting a second Linode until you had exhausted one of the higher levels (720? 1080?), otherwise you're creating needless extra work for yourself.

Such upgrades can be done relatively painlessly (without getting a new Linode).

Your database server will be much happier on its own box.

~JW

You mean by itself on a 360 with 2x as much contention with other 360 users, or together with your web server on a 720 with a lower contention?

Personally I do not think it matters until you out grow your VPS and move onto a dedicated box, or are using some solution that's very horizontally scalable.