Size, Weight, and Power ? I've never seen this acronym before so am venturing a guess.
While the idea of splitting out disks would work, there are some things to consider:
- You now very likely increase the troubleshooting time and MTTR for a given VM because you've spread its storage interests among different systems, so an issue with one system will impact everything to a greater or lesser extent (because you now have all [potentially] VMs with at least one disk stored there).
- You will have different performance characteristics as a side effect to saving on capacity.
- If using a VADP-based backup application, taking snapshots is now more complex (and some apps don't take kindly) because vSAN uses one disk format while your external VMFS-based array uses another.
This use case is really almost like the "I-need-a-swap-VMDK-datastore" argument that sounds attractive on paper but, in reality and the givens that are failure scenarios, can come back to bite you in the rear.
I fully agree, troubleshooting will just be extremely painful in these scenarios, if not almost impossible. I wouldn't go there, although technically this is supported indeed, from an operational point of view it is a nightmare.
Thank you for your reply, I appreciate the answer, it lines up to my train of thought but wanted the second opinion. You were pretty close on the acronym, SWaP refers to Space, Weight, and Power.
Thanks Duncan, I'm a huge fan of your blog and keep your "Essential Virtual SAN" book close at hand on my desk. And thanks for confirming my thoughts, and giving me solid evidence to show my leadership.