Morning,

I currently own a single 360 Linode which I have the following on:

Lighttpd + FCGI PHP (with execwrap/suexec), MySQL, Postfix, Dovecot, Spamassasin, SVN.

There are around 5 domains that run PHP (so 5+ PHP processes all around 20mb each), 1 of those domains has around 5 subdomains (one of which is Ruby/ROR, not PHP). They are not exactly high traffic domains, apart from one which pulls in around 1.2/1.3million hits a month but still that isn't too much.

For a while I've always been using swap space, around 180mb of it - now after some recent tweaks to MySQL I've got that swap usage to 80mb, so much healthier (and faster) than before.

I've been debating with my self if to get another 360 which will purely run MySQL + Mail, or just upgrade to a 540. This morning I did actually buy another 360 and got it mostly setup, but something is telling me to not use it and either A) Upgrade to single 540, B) Tweak existing to get lower memory usage.

So, what would you advise, keep current, upgrade or continue to use additional 360?

Well, if you're actively swapping, you need to tweak more, or get more RAM. You can probably add RAM without moving up a plan.

Moving MySQL off to its own linode will make it much happier. If you are going to be spending more money, another 360 will give you more bang for your buck than a single 540.

If you're hitting swap, then you're already taking a huge performance hit. The secondary cost to that is if you're swapping, you have little to no memory available for caching disk reads. MySQL _really_ benefits from disk caching, especially in read heavy applications.

Speaking of caching... if you do decide to stick with your single 360 (or even if you go with a second 360). Have you looked at other caching options? You can take a big chunk out of your memory usage by caching at a couple different levels in your stack. Look at using memcached with Lighttpd and/or MySQL, and some sort of op-code caching for your PHP stuff (I don't run PHP, so I don't know what the options there are).

~JW

You're missing a poll option: Upgrade to a Linode 14400

I'd say either go with caker's suggestion or upgrade to a 540 plan and start caching stuff. Whichever is more financially available.

_________________
If it ain't broke, you didn't tweak it enough. If it is broke, use more duct tape.
http://independentchaos.com

You may also want to investigate how much RAM that Spamassassin is using. Content-based filtering can compete for memory and CPU with databases and http servers. A Linode I work on takes care of nearly all spam just using sanity checks and greylisting. A DNS blacklist is another low-resource option to consider, but I haven't found it necessary.