Should we install the OS on an SSD or not when running virtual machines?

Question

I have a new Dell Mobile Precision M6500 laptop with 8 GB RAM. it has two hard drives - 500 GB @7200 RPM and a 128 GB SSD. The main purpose of these laptop is software development in virtual machines.

The plan is to install the base OS (Windows 7) and all the programs in the 500 GB drive, and let the SSD only contain the virtual machine images. It is my understanding that the we get most performance from the virtual machines if the images are on a separate hard drive than the base OS. Is this the way to go, or should I install the OS on the SSD as well? What are the pros and cons?

The virtual machine images would be between 20 - 30 GB, and I might run 1 or 2 at a time.

Answer 1

One caveat to note: you won't get TRIM support from the virtualized instances, which means you'll lose performance over time on the SSD.

As to your original question, I see no reason to use the 500 GB for anything other than bulk storage (backups and the like); running the OS off of the SSD makes the most sense. The reasoning behind separating the disks hosting a virtual OS and the host OS only really makes sense in a world of non-zero seek times, so since SSDs have no penalty for non-linear access, I'd say combining the two is the way to go. That'd also let you remove the spinning disk entirely, which would save you quite a bit of battery discharge when you're on the road.

Answer 2

Certainly it'll be about as fast I can imagine it being (bar the use of FusionIO drives) - what I would say it that the VM's OSs will write as much they would on a regular disk in a non-virtualised environment, meaning write-wear. If that doesn't bother you then off you go.