SSD and HDD run together seamlessly in a computer, but should be used for different purposes.
Firstly, it useful to know the advantages and disadvantages of both. SSD offers faster read/write speeds and low power consumption, but storage is expensive. Whilst the opposite is true of HDD. So running them together offers the lightning speed of SSD with a large storage capacity.
SSD as boot drive
Consider using SSD as the boot drive which will contain the operating system. This will speed up all operations including launching programs, booting up and shutting down. The OS can be installed by fresh install or OS migration. For a fresh install use the Windows Media Creation Tool on the PC. To prepare make sure you have 8Gb of empty USB storage, an empty SSD an the necessary Windows product keys.
To save a lot of time use OS Migration to install the OS on SSD. EaseUS Partition Master is a useful tool that is free to download. Simply use the Clone > Migrate OS tool on the left hand menu. Before starting either process, it’s important to backup any important data to an external drive. It’s also important not to defrag the SSD. Data is fragmented on HDD but not on SSD. Defragging SSD will accelerate the degradation.
Store data files on HDD
As SSD cannot be filled to capacity, store data files on HDD. To speed up the read/write process be sure to defrag the HDD and complete a Disk Cleanup. This will clean up unnecessary system files and free up more space. If you get a Low Disk Space error, the Temp folder maybe quickly filling up with application files (.appx). Reset the Microsoft Store clear the Store cache and run the Windows update troubleshooter Start > Settings > Update & Security > Troubleshoot and select Windows Store Apps from the list and Run the troubleshooter.
Further reading
How do HDD and SSD data recovery techniques differ?
Wear levelling and SSD lifespan
Should I disable TRIM on my SSD