I'll be glad to do so,
@HardChargin - I'll try to give fairly detailed instructions; please don't take offense and think I'm being condescending or anything like that if you already know about most of this stuff. :)
I had already installed the update on my FreeNAS server, not realizing that the new version required a firmware update for the on-board LSI HBA. Ooops! I have good backups, so I didn't bother with unplugging the hard disks or taking any of the other steps you described. Your needs may differ in this regard. In any case, my pool loaded up just fine after flashing the HBA.
Before you begin, note that you will need to know the controller's 16-digit SAS address, as the script provided by Supermicro will prompt you for the last 9 digits of it. I had noted down this information when I first constructed the server. If you don't have it handy, you can boot the system and load the LSI option ROM code to get it. (It may also be stamped on the motherboard itself, if feeble memory serves.)
I downloaded Supermicro's P20 firmware zip file (PH20-IT.zip) at this link:
ftp://ftp.supermicro.com/driver/SAS/LSI/2308/Firmware/IT/
Using
Rufus on a Windows 7 PC, I created a bootable USB stick and extracted all of the files from the zip archive's \UEFI folder onto its root directory.
I also put a copy of SHELLX64.EFI onto the USB stick, but unfortunately I don't remember where I obtained it - and I don't think this file is required as I used the motherboard's built-in EFI shell. On reflection, I'm not even certain the USB stick needs to be bootable, since, again, I used the built-in EFI shell.
After gracefully powering down the FreeNAS server, I used IPMIView's KVM console on the same Windows 7 PC to mount the USB stick as virtual media on the FreeNAS server. I then powered up the server, entered 'Setup', and loaded the built-in EFI shell:
View attachment 8507
After the UEFI shell loaded, I entered 'fs0:' to select the USB stick as my current drive. (Note that your USB stick may not be located at 'fs0:' and you may in that case have to find it by trial and error.) Here is how my screen appeared after also entering a dir command to show the files on the USB drive:
View attachment 8508
Once you (finally!) get to this point, all you need to do is execute the Supermicro script by entering SMC2308T.NSH at the command prompt. After trundling along and doing its job, the script will eventually ask you for the 9-digit SAS ID. Once it completes you're done and can reboot the system.
Good luck!