Could be a RST GUI bug or limitation for RAID ready to RAID a GPT system drive with another or just that it can't boot a RAID a GPT which is the RAID ROM limitation but really its better to setup the RAID before installing the OS which will require for drivers as your installing for GPT support should Intel RST be able to boot a RAID on GPT.
I had read that 11.5+ supported large disks which would imply GPT support. I also read that it supported UEFI.
I didn't want to reinstall my entire system when RAID ready to RAID is supposed to work. Hopefully someone else has seen this and knows a work around.
Responding to this old thread because I'm having the same problem on a pair of 500Gb drives. Just got an Asus P9X79 motherboard installed with Win7 x64 on a dynamic GPT disk and UEFI boot. Latest BIOS, latest IRST drivers (184.108.40.2063). Both disks were put in a RAID1 array and then I did a new Win7 install. So far so good. Then I started trying to get SRT enabled and, like many, couldn't get the Accelerate button to appear. Having no luck with that, I decided it was time to move on.
One of my reasons for using RAID1 is for easy backups. I have three 500Gb drive (all are WD500AAKS). To create my first backup, I shutdown and unplugged drive 2, plugged in drive 3 and rebooted. As expected, the array was in degraded mode. But before I went to rebuild the array, I noticed that the Accelerate button was now showing up in IRST! More troubleshooting trying to get SRT to work led to wiping the system off drive 1 (by creating a new array from the IRST rom). No problem, still had my drive 2 mirror. Shutdown, plugged it in, but couldn't boot from it. Went into IRST rom and reset it to non-RAID volume (that's not the same as setting it to AHCI, which I did not do) and then was able to boot from it.
That's the sequence of events that led to the current state - the RST app will not let me build a new RAID1 array with drives 2 and 3, keeping the data on drive 2. I get the exact same error messages as the OP. If I try to accelerate drive 2, I get "An error occurred and the selected disk or volume could not be accelerated." and in the event log this error "Error: Action failure, Action request timed out DiskSetCacheMode".
Can Intel confirm if the combination of dynamic GPT disk and UEFI is the problem? I was unable to find anything on that specific combo with a less
than 2Tb drive here or anywhere else.
Successfully accelerated a RAID1 volume keeping the data on one disk. It was non-system, MBR, and basic. So system is working fine. Next test is non-system, GPT, dynamic disks.
Message was edited by: cb4 Added test results.
Try creating a RAID 1 again but with a lower partition of the 3 TB hard drive. It is possible the 3 Tb hard drive is too high for a RAID 1 on a dynamic GPT disk and UEFI boot.
Answer to original question.
If you have data on the bigger drive shrink the main c drive partion using windows disk management by about a gig. You should then be able to intel rapid storage to create RAID 1
This fixes the "SSI Status: Invalid Size" issue.