So I'm seeing some strange, slow behavior with a simple Storage Spaces pool with only a pair of mirrored drives. I've seen lots of folks having problems with SS, but most are issues with parity spaces.
I've got a new Dell R730xd with 4 of their 400GB nvme ExpresFlash SSDs. The machine also has a PERC card with a bunch of 15K rpm SAS drives and will be used for SQL Server. (and a pair of E5-2643v3 xeons and 256GB ram)
This is running Windows Server 2012R2 with all the latest patches. I've used both Storage Spaces / pools and traditional windows disk management to create a mirrored pair of these drives. I also tested a single drive by itself. The SS volume actually showed huge promise for a moment where it was obviously reading simultaneously from both drives. These are some of the fastest SSDs available now, so these results for just using a pair of them are pretty awesome. Using the old-school windows disk mirroring does show a performance penalty vs. a bare drive, but it's not drastic, so it's probably what I'll be forced to use unless I can fix the problem.
*note I later rebuilt this pool using a 4k physical & logical sector size hoping that was the culprit, but it didn't help. It sorta looks like I'm running into some PCIe bus contention, possibly overloading the backplane. *shrug*
You can see the PS syntax used to create this here:
photobucket image
And here's what a single drive looks like by itself: