VMware Memory Usage
Recently this question came accost my desk: VMware MUI (Management User Interface) tells me that a systems memory usage is less then what is allocated. How can this be when in the host OS it is using all the ram?
VMware has a few tricks up its sleave and I want to touch on two of them at the moment.
Memory trimming
VMware checks which part of the guest OS virtual memory is not used and allocates it back to the host OS. This permits to have more concurrent virtual machines running but everytime the guest OS asks back for its memory it suffers a performance degradation.
So, if you have enough free RAM for all planned concurrent VMs, be sure to disable memory trimming for guest OSes.
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.
January 25th, 2007 at 11:43 pm
Vmware is awesome, it gets awesome each release. I can’t tell you it saved my life.
January 26th, 2007 at 10:25 am
gah, i can’t type