Share RAM between VM's when Load is Low

[dirtbikedude]

Hey there,

I'm running Windows XP on the host and I'm running VMware Workstation 6 and I have about 7 VM's that are all running Windows XP. Now the host machine has a limited amount of RAM to run all the VM's symultaneously...however not all the VM's are being used at the same time and not all the VM's are using all the RAM that they're being dedicated. Basically what I'm asking is if it's possible to some how load balance the RAM distributed to these virtual machines. So for example when a VM goes idle and the VM is on but it's basically not running any programs and say for example 256 RAM that was dedicated to it is just being wasted, is it possible to distribute the free RAM that it's not using to VM's that are not idle? Or is possible to automatically dynamically change the amount of RAM in the VM while it's idle so that it can be re-distributed to VM's that need it?

Thanks

[RDPetruska]

No, this is not possible with any of the hosted products. For these kinds of features (memory page sharing) you need to use the virtual infrastructure platform (ESX/ESXi).

You typically do not need as much RAM with virtual machines as you do with physical ones, but it depends on your usage. Also, if you don't need any DirectX graphics in your guest, you can disable the 3D graphics interface and save RAM used by the guest, as the virtual video card uses more RAM when the 3D graphics is enabled.

[KevinG · Accepted solution]

For Hosted products:

Memory Trimming

Workstation uses a memory trimming technique to return unused virtual

machine memory to the host machine for other uses. While trimming

usually has little impact on performance and may be needed in low

memory situations, the I/O caused by memory trimming can sometimes

interfere with disk-oriented workload performance in a guest.

You can disable memory trimming for a guest in the virtual machine settings editor (VM > Settings > Options > Advanced). In the Settings section of the Advanced panel, select Disable memory page trimming.

Page Sharing

VMware uses a page sharing technique to

allow guest memory pages with identical contents to be stored as a

single copy-on-write page. Page sharing decreases host memory usage,

but consumes system resources, potentially including I/O bandwidth.

You may want to avoid this overhead for guests for which host memory is

plentiful and I/O latency is important. To disable page sharing, add

the following line to the virtual machine configuration (.vmx) file:

sched.mem.pshare.enable=FALSE option