it depends on the server you are putting it in. For a PC as a server it would be great, but if you need Fully Buffered or ECC ram (which is required by many servers) then it simply will not work for you.
Also, it depends on your use. If it is for a home server it will be enough (lol, more than enough most likely), but if this is something a little more demanding then you may need more. I know my network guy at work says he requires a minimum of 2GB per core/thread on the CPU, and preferably 4GB to keep everything moving nicely. That means you should preferably have 8GB on a duel core, 16GB on a quad core, 32GB on a quad core with hyper-threading, 48GB on a Hex core with hyper-threading, and lastly 64GB on a 8 core or duel quad cores with hyper-threading.