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I have an ESXi (v4.1 U2) box with 16GB RAM and 8 CPU cores available.

The full stack will incorporate 2 CentOS 6 instances:

1) DB Server

2) Web server  
Apache httpd load balancer
2X Jetty App. Servers (Scalatra + Scalate + ScalaQuery)
Jedis cache

Resource-wise I should be fine, but am wondering what impact/benefit there is in going 64-bit with this setup? Apache will utilize Google mod_pagespeed with in-memory cache; Jedis is obviously in-memory as well.

I'm looking for max performance.

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up vote 7 down vote accepted

There's no good reason to use a 32-bit OS for new deployments on modern hardware. You want to be able to address and utilize the resources available to you. Even if you deem that 32-bit is sufficient, 64-bit will be more future-proof. Finally, there's no easy move from 32-bit to 64-bit without a system reinstallation. From an administrative perspective, that's the biggest reason to use 64-bit.

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right centos 6 has no upgrade path from 4 or 5. Had read some horror shows re: significant increase in memory usage with 64-bit, so just trying to cover the bases. – virtualeyes Feb 26 '12 at 23:30
agreed. there are only a couple of good cases for 32 bit such as when your app has a small heap size and all that extra addressing space is unneccesary. – Tom H Feb 26 '12 at 23:41
@TomH, and even then when you realize you need to scale your application you'd have been better off to start with 64-bit :-) – Kyle Smith Feb 26 '12 at 23:58

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