I hope the title of this post doesn’t surprise you! This is sometimes a forgotten design of ESXi when choosing your boot options. I have been increasingly talking with VMware admins that are deciding to mirror their local drives for ESXi. This seems to be a common design on blade architectures as well, where they use the two open drive bays for mirrored ESXi boot images.
The question to ask, is why do this? If ESXi runs entirely in memory what benefit do you have in mirroring two drives? Yes, you do have another copy of the image, in case of corruption, but wouldn’t it be easier and less wasteful to just store a copy of the image on removable media or use image builder for the resiliency!
Most server architectures are including internal SD cards or USB flash inputs to install ESXi on and there is of course the use of VMware’s Auto Deploy! The use of one of these methods for ESXi boot will not only save resources but will open up more opportunities for new technology usage.
There are many examples of converged storage architectures that would require you to use all available drive bays to maximize capacity usage. Then there is also the use of server-side flash technologies, like PernixData FVP. Having multiple options for local flash will provide more possibilities when you want to create tiers of flash for your differing workloads.
The point of this post is to hopefully illustrate that you don’t have to mirror ESXi for fault tolerance. There are many other alternatives to protect your image and why waste resources on something that could hinder the growth of your virtualized datacenter.
For added reading pleasure, here is a link to some entertaining conversations about installing ESXi on local disk or local USB.