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I recently got a side job migrating a website from shared hosting to a VPS. The site is running on Django + Apache (mod_wsgi) + MySQL. The current host is running CentOS 5.6 (32-bit); should I take advantage of the move to switch to CentOS 6? And given the choice of 32-bit or 64-bit CentOS, should I stick with 32-bit or switch to 64-bit?

(I'm more experienced with development than with sysadmin stuff, hence my question. I also know Debian/Ubuntu much better than CentOS, but I'd like to get familiar with CentOS, and this is a fairly low-complexity setup to get started with.)

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up vote 2 down vote accepted

There are several PROs and CONs:

5.x vs 6.x

  1. Does your new provider actually support CentOS 6.0 right now? For example, Rackspace Cloud only promises Centos 6.0 support "soon", right now you'll have to start with 5.6.

  2. Do you value more recent packages or you need to support legacy software, especially closed-source built for version 5.x? If you don't need to support older software, I'd say start using newer version.

  3. Do you know there's no upgrade path from 5.x to 6.x? E.g. you'll have to do a complete re-install if you install 5.x now but need 6.x later.

32-bit vs 64-bit

  1. What does your hosting support? Some provide only 64-bit or only 32-bit supported platforms? E.g. some Amazon cloud instances are only 32-bit, and Rackspace cloud instances are 64-bit only.

  2. Generally speaking, 64-bit system takes more RAM to do the same job as 32-bit system. However, it can also support and efficiently manage more memory. If you're planning 4GB server or larger, by all means, 64-bit is the way to go. If, on the other hand, you'll have 2GB of memory in your server, you don't really need 64-bit, and 32-bit system will manage your existing memory with less waste.

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Thanks, this is great advice. I ended up going with 6 because I have no reason not to, really, and if it really doesn't work I can switch out for 5.x. And since this VPS is only configured with 1 GB of RAM (and I can't imagine it needing over 4 GB anytime soon), I don't need 64-bit and 32-bit will save me some RAM. – mjjohnson Oct 6 '11 at 3:53

So long as you retain the ability to "fail-back" to the known-good server at the old site, this is a worthwhile way to do upgrades.

We actually moved a whole datacenter two years ago by doing a P2V conversion of all servers in an incremental fashion. Worked like a champ, and we had the ability to fail back to the old physical server at the old site if something was wrong.

Have a test plan handy to make sure everything actually works right on the new site before flipping any switches (DNS).

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Thanks, that makes sense; might as well get the newest version while I'm moving everything over anyway. I'll be holding off on switching DNS over until I'm satisfied the new server is performing well. – mjjohnson Oct 6 '11 at 3:50

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