Question OS migration to SSD completed and boots, but can't leave old HDD connected.

[KageXY]

I want to preface by saying I am not the most knowledgeable when it comes to PC parts and components, so please bear with me.

I finally went around to installing a Samsung Evo 870 1TB SSD I got a while ago and saw some threads about how using it as the boot drive, as opposed to the HDD, is a night and day difference. I went through the process of cloning the old HDD and everything onto the new SSD using Macrium Reflect. Once the process was completed, I turned off my new PC, disconnected the HDD, and tried booting up solely using the SSD. It worked, thank f*cking Christ because I spent more time than I would like to admit yesterday trying to get this process to work. I will admit, it really makes a world of difference having the OS on SSD - my PC booted faster, apps opened quicker, etc.

However, problems arise when I reconnect my old HDD. The reason for reconnecting the HDD was that I figured I would keep it for the additional storage. I didn't see a point in spending money at the moment when I had a 1 TB hard drive that I could easily format and use. When I reconnect my HDD, the PC wants to boot using the HDD only. I tried going into BIOS (I own an MSI z370-a pro mobo) and changing the boot order, only for my SSD not to be listed in the "HDD boot priorities" drop-down menu - it only has 2 Windows boot managers listed. I assumed that the Windows boot manager just took the place of the SSD name so I tried to change the second boot manager to the first priority and save, but when I saved it said I made no changes.

I am currently booting in RAID/Optane Mode with my SSD as opposed to the AHCI mode that I have seen people recommending. When I switch to AHCI mode and try to boot, it gives me a BOSD with the error "inaccessible boot device". From the reading I have done, it seems this is happening because Windows was initially downloaded on the HDD in this "Raid/Optane Mode".

This brings me to a few questions:

- Is there any way to boot from SSD in this "Raid/Optane" mode with the HDD connected?
- Does switching to AHCI mode really make a big difference in the performance of my SSD?
- And if this AHCI mode does make a significant difference in the SSD performance, is there any way to fix this "inaccessible boot device" error without doing a fresh install of the OS onto the SSD?

Again, please bear with my lack of computer science knowledge lol.

 

[Ubrales]

If all you want to do is to format he old HDD so that you can use it as a storage device, do the formatting on a different PC. It will work fine. NTFS I think.