Azathoth wrote:
You're looking just at RAM. What about disc? If you cram all those services onto a 256 node, and there are twice more nodes on the host than with 512, what do you get? The services you listed, especially Postfix and Postgres are disk intensive. In fact, any service that touches the disk becomes disk intensive because you don't have sufficient RAM for both their application needs AND filesystem cache, so each read becomes a real disk hit.
I'm not actually sure how much worse I/O contention would be with double the guests - it takes very few simultaneous guests even now on a Linode 512 to dent the I/O bandwidth, so the odds are already pretty high.
Certainly, a database server can be disk intensive, but it's very server, schema and application-specific. In my case, even a 256MB Linode and twice the guests per host would have sufficient caching to manage the database load with a responsive application, at least for several more sites than I'm at now. And of course for the web server, everything would pretty quickly be completely cached in memory even on a 256MB Linode.
Not everything is a large Drupal or Wordpress (or equivalent "heavy" application server) site.
Still not trying to argue for the offering, but it's only fair to point out that there's a lot you can do in 256MB :-)
-- David