Scenario: Single 500GB HDD and single 240GB SSD. I wanted to use SSD cache feature to accelerate hard disk access. Both HDD and SSD are initialized as GPT, with the “system” disk containing a Recovery Partition, an EFI System Partition, and the C: drive (Boot Partition), with the entire disk allocated. The SSD is shown as Unallocated. Intel’s Rapid Storage Technology would not let me enable their Smart Response Technology (SSD caching), however. The only performance accelerator in the Rapid Storage Technology UI was for Dynamic Storage Accelerator.
On my HP EliteDesk 800 G1 SFF, I had to change the disk access mode in the UEFI/BIOS from AHCI to RAID. Windows then failed to boot (no surprise there). After switching back to AHCI, I followed the advice from the following post to reboot in Safe Mode to enable RAID access, and that worked. If I recall correctly, in Windows’ Device Manager, there was no obvious Intel-provided driver under Storage Controllers until after I enabled RAID mode – only a “Microsoft Storage Spaces Controller.” I obtained the most recent version of the driver from Intel, but was still unable to enable SSD caching.
After following advice from Tom_GPT on the following thread, I shrunk my C: drive by 1GB (that size was arbitrary). This resulted in 1GB of unallocated space at the end of the 500GB hard disk. I was then able to launch Intel’s RST and enable Smart Response Technology. Using Intel’s latest versions of both their RST and storage drivers is probably advisable.