How much RAM?

[TheBaconator]

I don't know where this should go, so if this is in the wrong section, please tell me.

I plan on owning a server soon that has FTB Unleashed with about 10 additional mods. How much ram would I need per person I would have playing on it? I plan on hoping to be able to have about 5 on at a time at least. How much would that be on average? Also, how much PermGen should I have allocated?

 

[DZCreeper]

For PermGen I usually do 128 although I run 256 with my current setup of 124 mods.

As for memory, I would plan on 1 gig per person. Maybe a bit less depending on your view distance you set and how much automation the players build.

 

[Connor Gavitt]

A whole GB per person? That's a bit much I use 3G For 70 people on unleashed however I have such a extremely large world and lots of chunks loaded so about 18GB is used for my world. But for a new river with 10 ish people 5GB ram should be more then enough. 3GB will even cut it if you use the right JVM arguments. If you don't plan on going to the farlands and stay within 10k 2GB of ram will be enough.

 

[DZCreeper]

I always plan for 1 gig per person because I don't compromise. I set the server view distance to 15 so people can fully utilize far render distance on the client. I also don't limit chunk loaders or large scale automation.

 

[Connor Gavitt]

I always plan for 1 gig per person because I don't compromise. I set the server view distance to 15 so people can fully utilize far render distance on the client. I also don't limit chunk loaders or large scale automation.

Still I think it is unneeded, the CPU takes the hit most when more chunks are loaded. But if you do get 1GB per person you will never run low

 

[Harvest88]

I always plan for 1 gig per person because I don't compromise. I set the server view distance to 15 so people can fully utilize far render distance on the client. I also don't limit chunk loaders or large scale automation.

My rule of thumb is half of that 512mb per dedicated slot taken up. So my 4GB server should be able to take about 8-10 slots 24/7. That should be fine for about 10-15 dedicated players.

 

[Connor Gavitt]

Also depends on your JVM. Arguments, they can lower the usage a lot.

 

[keybounce]

Best bet is to start by adding some logging flags, so you can see how much memory is actually being used.

-XX:+PrintGCDateStamps -XX:+PrintHeapAtGC -XX:+PrintTenuringDistribution -XX:+PrintCommandLineFlags -XX:+PrintGCDetails -Xloggc:GC.log

That will log a lot of information, along with timestamps, so you can cross reference what you were doing (or, from the server log, what was being done) when it happens.

 

[TheBaconator]

Alright thanks everyone.

 

[Francis Baster]

For PermGen I usually do 128 although I run 256 with my current setup of 124 mods.

As for memory, I would plan on 1 gig per person. Maybe a bit less depending on your view distance you set and how much automation the players build.

Rather than using a rule of thumb such as 1 gig per person, it is better to actually monitor your heap and perm space usage with a remote JMX or similar. Allocating large quantities of memory to Java will cause it to run slower, especially once you exceed 32GB and start using compressed OOPs. It is usually not recommended to allocate much more memory to Java than it actually needs.

I apologise if I'm insulting your intelligence, but with memory you either have enough or you don't, there is no incentive to have much more than you need. The resource you need to have an excess of for demanding servers is single-threaded CPU power.