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Within the next couple of days, I'm going to need two Linux VPS instances (probably Ubuntu 10.04), one running PHP and one for Ruby on Rails. Both are most likely going to use nginx and MySQL and have about 256-512MB RAM.

Now the question is, should I go with a 32bit or 64bit system? There is a related question already posted, but without any specific information on how to decide.

How does 32bit vs 64bit system behave from your experience in these conditions? (Ruby/PHP, nginx, MySQL)

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up vote 2 down vote accepted

One of the biggest factors to consider when choosing between 32 and 64bit OSs is growth. With a 32bit OS you'll hit the ceiling on performance when you hit 4gb of RAM. With a 64bit OS the performance ceiling is basically whatever your your budget will allow. Judging from what you're describing, unless you're expecting to grow really fast I'd say you're probably fine for a while.

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It depends, we have 32 bit (pae) kernels here using 48gb of ram. – Sirex Oct 17 '11 at 13:33
@Sirex: PAE does work; but as ErnieTheGeek said, you get a performance hit. Simple truth is that with few exceptions, below 3GB, 32bit is faster; and above 4GB, 64bit is faster. And, of course; if you want to run some single-process task (even if multi-threaded), PAE won't allow it to get more RAM. PAE helps when you run several processes on the same machine. – Javier Oct 17 '11 at 13:53
true. but it depends if that performance hit is noticeable, and on the workload. Often it isn't, in my experience at least. Just think often 64bit gets touted as a silver bullet, which it isn't. – Sirex Oct 17 '11 at 13:59

32bit. You have a very small amount of ram, hence wont need to address a large amount (4gb+) from any one process. 64bit will likely actually run slower in these instances.

... then again, ruby might be some special case - i don't use it.

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