"Its Time To Expand" Indicators?
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
5 Replies
@BarkerJr:
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
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).
~JW
@JshWright:
Your database server will be much happier on its own box.
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.