That's an expensive way to provide some HA. What's the business requirement? How does that tie into Postgres? Might be able to do it in other ways.
We used to run a SAN shared between our host servers, but this was replaced with Storage Spaces. I think they don't trust Postgres native HA capabilities and want some hardware guarantee.
Yikes! Yes, SSD would be a big win. It's orders of magnitude faster, and just removes so many problems.
I assume it will help, but I fear however that the overhead with a 3 way mirror is not going to be solved with just adding SSD. I'm trying to get them to rather deploy direct attached NVME/SSD to each Host and then use PG HA from there.
Sorry, I have no numbers to provide you there, but I cannot imagine any amount of tuning is going to be as big a win as going to SSD.
It does take a lot of convincing and arguing though, so concrete number help get the point across.
Thanks for the response
