How much memory for Windows 7 guest?

[ajbrehm]

I am running VirtualBox (current version) on Mac OS X (current version) in 32 bit mode (although I want to switch to 64 bit mode).

My computer (Cyrus) has 8 GB of memory. The Windows 7 VM (64 bit) runs headless all the time. I connect to it via RDP whenever I need it. There is also a Linux VM running all the time.

I am wondering how much memory I should assign to the Windows VM. The Linux VM has 1 GB and is not used for much. I probably can reduce its memory footprint to 512 MB.

Since I actually use Windows 7 quite a bit, I take it as read that it should use at least 4 GB.

So what is best of the following options (or does something else make sense)?

I. 2 GB (Windows 7), 1 GB (Linux), leaving 5 GB for Mac OS X and other VMs (that run only occasionally)

II. 3 GB (7), 1 GB, leaving 4 GB for Mac OS X

III. 4 GB (7), 1 GB, leaving 3 GB

IV. more than 4 GB (7), 1 GB or more (Linux), buy more RAM

For option IV I have to add that my Mac Pro has 8 slots for memory 4 of which are used (4x2 GB). I understand I have to add memory in 3s or 4s.

I have also assigned two virtual CPUs to both VMs. The Mac has two 4-core CPUs.

[ajbrehm]

I found out that running the Windows VM with 3 GB on an 8 GB host makes it very slow. I switched to 2 GB and it's much faster.

I think this has to do with swapping. If Windows thinks it has 3 GB of physical memory it will think it's not swapping even though the host might be. If Windows thinks it has only 2 GB, it will think it's swapping, although the host might not be (thus creating very fast swap space).

[Trikks]

I have the same problem with 4.0.4 running Windows 7 on a Snow Leopard host with 8gb ram. A very strange thing is that the windows v-host is very slow even when booting up.

I've experimented a bit and found that the limit seems to be 2560 MB (1024 + 1024 + 512), if I try to add 256 MB more the machine fails miserably. This is a fact on three separate machines that I have access to.

But it's ok for now, I'll try to keep my pagefile to a minimum (256 - 512 mb) and make it a bit bigger when I bought one of those SSD drives.