RamDisks have been used on Macs since the early mac classic days. A RamDisk is in essence a virtual disk using your available RAM. It will be faster than any HDD or SSD.
If you have a lot of RAM on your mac, you can easily make a RAMDisk in the terminal.
Here is how you make a RAMDisk:
diskutil erasevolume HFS+ “ramdisk” `hdiutil attach -nomount ram://xxxx’
Replace xxxx by the number of megabytes (MB’s) * 2048. For example, if you want a 8GB ramdisk, use 8192*2048 = 16777216. You can use whatever name you want for the mounted volume in double quotes.
Copies are insanely fast. Typical benchmarks tools like Black Magic cannot even run.
There are plenty of good use for ramdisks - scratch, working on projects like database with lots of I/O. Ramdisks are great at being source drives for testing the write speeds when benchmarking drives.