Recently I picked up some of the new Seagate FreeAgent GoFlex drives with the swappable interface dongles since we've had good luck with the previous generation of drives and we were interested in seeing if we could eek out a little bit more performance by changing interfaces for it. Running virtual machines off external hard drives is slow enough as it is so every 1MB/s you can get is a plus to me. My test platform was a Dell Latitude e6410 and a 500GB GoFlex drive with both the USB 2.0 and eSATA dongles.
First I tried out a few large file copies (500MB to 2GB) and noticed that windows was reporting a higher sustained rate for the USB2.0 but I also noticed a very long delay on the last 1-2% which I'm pretty sure was a cache delay. This delay at the end offset the perceived higher transfer rate that the USB transfer had shown. The eSATA transfers all went smoothly with no lag at the end at all. What can I say, I liked the honesty of the eSATA estimates better.
I then tried out some disk benchmarking tools like CrystalDiskMark (below) for further data and fortunately they all seemed to show the same significant advantage toward the eSATA:
Now I'm by no means an expert but I think eSATA will be the way to go for my Virtual Machines. At the very least the high sequential read/write should make the startup/shutdown for the VMs faster than they currently are under USB. So I shall sent out my little guinea pigs and wait for Murphy's law to kick in...