On Tue, Feb 10, 2026 at 6:13 PM Riaan Stander <rstander@exa.co.za> wrote:
3 x Host Servers running Microsoft Storage Spaces in a 3 way mirror
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.
but at some point it came to light that the Storage Spaces hardware are all mechanical disks with NVME only used for Storage Spaces journaling and caching. There are now some discussions of upgrading drives to SSD, but my concern is that this is not guaranteed to solve the issue. Especially with the 3 way mirror it seems all writes will go to the other hosts before returning. So latency is almost impossible to remove.
Yikes! Yes, SSD would be a big win. It's orders of magnitude faster, and just removes so many problems.
So now my question. I started running some IO tests using fio, pg_test_fsync & pg_test_timing. Before we spend days/months trying to tune Postgres settings I'm trying to get some definitive published information about what IO numbers I should expect when running plain hardware tests with Postgres completely out of the loop.
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.
