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32-bit operating systems can only 4 GB of RAM unless they use PAE. In addition, the operating system reserves several hundred megabytes of this for its internal cruft. I would like to optimize my virtual machine so that it has the maximum amount of usable RAM while not wasting host's RAM for unnecessary allocation.

So what would be the amount of RAM which would allow me to have maximum addressable RAM in a 32-bit virtual machine without wasting anymore RAM than necessary or using PAE in the virtual machine. I expect this amount to be somewhere between 3 and 4 GB but I would love to know the exact value.

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You need to supply details on what these instances will be running. If they're sitting there, you can probably set it to 512MB. If you're running Oracle, you probably will need more. – cjc Sep 11 '11 at 12:36
How can we possibly answer this? You don't give us any details at all. It would be much easier for you to simulate what you think your average load will be and then check out top and see where you're at. – MDMarra Sep 11 '11 at 13:17
I edited the question because it appears that my question was mostly misunderstood. – lhahne Sep 11 '11 at 16:12
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closed as not constructive by mailq, SvenW, MDMarra, sam, Ben Pilbrow Sep 11 '11 at 13:36

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The question has no answer: you will need as much memory as necessary for the applications running in the VM. You can go from a few megabytes (you can have Linux systems on small embedded systems) to gigabytes: it's a matter of what you need to do in the VM.

You should ask you:

  • what do you want to run (applications, memory footprint)
  • which part of a Linux distribution do you need to run your applications

And being the VM virtual gives you the possibility to experiment. Start with less, run your stuff and see if it's enough (e.g., by looking at swap space usage).

If it's too much increase it, if memory is never used decrease it.

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