x86 OS, RAM, & Virtual Machines

[Myke 0]

I feel pretty certain that virtual machines use alloted RAM based on the RAM that is currently installed on the host machine. If I am wrong, please let me know, as that will probably answer my question, which is this:

 

x86 operating systems can only use a maximum of 4 GB of RAM, plain and simple. Given that the VMs are using these 4 gigs of RAM, would adding additional RAM to the system (provided that the mobo can handle it) allow the VMs to use that RAM? I know the OS cannot utilize it, but it kind of makes sense to me that the VMs should be able to use the extra RAM.

 

The reason I ask is because I'd like to increase the RAM used on some of our VMs, but it's not letting me because it says there isn't enough to use. One VM uses 2 GB of RAM and the other uses 1 gig. I'd like to boost the 1 gig machine to have more RAM without affecting performance on the host machine by using all of the alloted RAM. Unfortunately, this is a live machine and I cannot really use it as a test environment. Nor do I have any other systems that I can really test this out on.

 

Can anyone share some knowledge with me regarding this topic? Thanks in advance.

[danleff 0]

Don't know what systems that you are running, but does this article help?

[Myke 0]

Definitely an interesting thing to note; thanks for the article. It still leaves me with the questions of being able to use the extra RAM on the host, even though the host's OS is x86. I don't mind limiting each VM to under 4 GB of RAM.

[jmmijo 1]

Originally Posted By: Myke

Definitely an interesting thing to note; thanks for the article. It still leaves me with the questions of being able to use the extra RAM on the host, even though the host's OS is x86. I don't mind limiting each VM to under 4 GB of RAM.

Basically you are limited to what the chipset can access as well, many chipsets only support somwhere between 3.0 ~ 3.4 GB even with an x-64 bit OS.

In order to allocate more memory to the a VM your host os and chipset have to support more RAM and also have more memory installed in that machine.

I wouldn't allocate to much ram to the VM in case your host os needs more to run properly.

[Myke 0]

The chipset and board can support a lot more RAM, but the OS (being x86) can only support 4 GB max. Maybe we should have planned this better, but too late now.

 

As for your last point, that's why I've been afraid to really test this out. Wish I had a spare machine to use as a test environment, because I can't exactly risk crashing 3 systems at once.

 

Thank you for your input; it is much appreciated. It's a shame that searching for information regarding this topic isn't widely available, as I assume a lot of people are a bit confused with this as well.

[jmmijo 1]

Originally Posted By: Myke

The chipset and board can support a lot more RAM, but the OS (being x86) can only support 4 GB max. Maybe we should have planned this better, but too late now.

As for your last point, that's why I've been afraid to really test this out. Wish I had a spare machine to use as a test environment, because I can't exactly risk crashing 3 systems at once.

Thank you for your input; it is much appreciated. It's a shame that searching for information regarding this topic isn't widely available, as I assume a lot of people are a bit confused with this as well.

With a later chipset and an x64-bit CPU, it would have been better to use an x64-bit Host OS for sure, but of course hindsight is 20/20 isn't it

Both Windows XP Pro x64-bit and Windows Server 2003 x64-bit have been out for a long time, I would have looked into these flavors for a host OS or the myriad of *nix flavors/distros out there too....

I've been playing around with both VMware Server and Virtual Box for a long time, but it's because I've always loved playing around with VM's along with my still working LEGACY machines like my C64's and Amiga's hehe