Here is the link to AMD STOREMI User Guide: https://www.amd.com/system/files/2018-04/AMD-StoreMI-Users-Guide.pdf
You must not have RAID active on your computer.
STOREMI only works with a SSD and TWO DRIVES.
From STOREMI User Guide link above:
Check the following prior to upgrading your system to StoreMI:
• Your system meets the minimum configuration: AMD socket AM4 processor and 4xx series motherboard with a minimum of 4G RAM (6G RAM to support RAM cache)
. • Secure Boot is NOT enabled. Consult your system documentation for further details.
• There are no SSD caching or AMD software RAID solutions installed
• The BIOS SATA disk settings are set to AHCI, not RAID and there is no software RAID installed on the system.
• Microsoft’s chkdisk or other third-party disk scan tools run error free on the boot drive
• A new unused SSD or HDD is available
• If wishing to use bootable tiers > 2TB in size, the system must be configured to boot in UEFI mode with a UEFI bootable Windows OS installation as Windows 10 does not support > 2TB boot drives in legacy boot mode.
From AMD STOREMI FAQ: https://www.amd.com/system/files/2018-04/AMD-StoreMI-FAQ.pdf
From above link at FAQ:
How many drives does this work with?
StoreMI for AMD socket AM4 processor works with 2 physical drives.