i have run 768mb, 1024mb and 2048mb ran servers with only nis.. only the 2048mb ram server seems to be stable.. the smallest one lost connection to nis(when looking as ncc) quite frequently.. 1024mb was better but still an issue.. 2048mb ram server is running a spam bot flawlessly without any error 500's.. i suppose this wont be the case after launch though seeing as the blocks wont be nearly/actually full..? 2gb servers are expensive :D
Yes i have problems too with VPS that has 1GB of memory.
Nis runs nicely for few days and then it goes stuck and can't resync any more.
It seems i will have to do an upgrade if i want to run it flawlessly
beside and other web app on the same VPS.