So you want to change the ESX pathing select to your datastores from MRU to RR, but the docs say you have to reboot ALL your hosts?
Recently I raised a request for my IaaS provider to change our pathing selection from the default MRU to RR. The tech/helpdesk person did some google searching on topic and got confused by the content, where the VM KB articles said to reboot and other articles were unclear, and so raised a support ticket with VMware and supposedly with HP to clarify. The response I got back from my IaaS provider was that both HP/VMware came back and said must reboot.
So I called bullshit on that, in fact, that’s the cheap/lazy answer.
The way it works is that, you can create a policy to map VMW_SATP_ALUA to VMW_RR_PSP, and it’s going to automatically apply it to any new devices being added – it only affects new storage sure, existing storage won’t change without a) host reboot or b) manually setting the paths on each LUN. A reboot is just the brute-force approach to save clicks.
I fully expected VMware Support to comeback with the “reboot your computer” answer, I got that same answer for many issues over the years since 3.5 (mostly that was about all you could do tbh), I was a bit surprised by HP also stating this given their own HP 3PAR + VMware 6 Best Practice Guide gives both options – Reboot or manually set the paths …
This is how I have always done it since ESX 3.5
Now, if I had 10 or more ESX hosts, then yeah sure, let’s reboot to save clicks!
It’s not to say that rebooting isn’t a valid choice. If you make quite a few changes across a system, a reboot might be needed to weed out quirks. In my case, it was impractical to do that due to various reasons and also unnecessary to perform vmotions across 100 or so VMs over a few days for what could be done in a few minutes.