I run the following off my 512:
Apache/PHP/MySQL
Ventrilo
Mumble
4 BNCs
Munin
Minecraft Server
I don't know if map size is more important or if number of players are, but my single "world" folder is 115MB. I _USUALLY_ have 0-4 players on at a time. A few times I've had 7-8 concurrent users.
My startup command
Code:
screen -A -m -d -S minecraft java -Xmx164M -Xms164M -jar minecraft_server.jar nogui
The Minecraft docs recommend 1024M for the min/max memory allocation. Any less than 164M with my setup seems to crash the server with Out Of Memory errors. I've had it up at 196M for a while without a problem and I've been slowly lowering it. This seems to be a good point for my setup. A minecraft server will always crash if you "stress" it by blowing up 1000s of blocks of TNT or something. If you have a bunch of people working normally and blowing up TNT here and there you should be fine.
If you run the server with this little ram you get
Code:
[WARNING] Can't keep up! Did the system time change, or is the server overloaded?
in the console all the time. It doesn't seem to cause any harm or degrade performance though.
I guess the bottom line is this: You don't need 1GB like the docs say. You could probably get away with running it on the same Linode as your blog. I'd start there and see if web performance degrades or if you have issues with the Minecraft server. Use top/htop to monitor memory usage. If you find you can't run them both at the same time you can either upgrade to a 1024 and increase the Minecraft memory to 512M, or just get a second 512 and play around with the memory limits. I would probably recommend getting a 1024 and running both at the same time, again monitoring usage with top/htop and checking reliability. If that still doesn't seem to be enough then go with a 1536 for both. I wouldn't separate them unless you need to.
Edit:
Hints that your Minecraft server needs more resources are Out Of Memory crashes in the console and blocks reappearing right after they're destroyed.
It's also worth noting my htop currently shows:
Mem: 261/469MB
Swp: 145/255MB
I'm not thrashing though so I assume that's just the kernel putting stuff that doesn't get used into swap to free up RAM. Also I'd like to point out that MySQL isn't optimized on my system. Minecraft currently has ~12 processing and is using "29.9%" of my RAM, which I assume includes swap.