Whether it was a hard drive (HDD), a solid-state drive (SSD), or an optical drive ... There have been a few alternative SATA interfaces over the years, like mSATA for laptop drives, which debuted ...

2 drives, 2.5-inch drives, and even mSATA, PCIe and U ... have room for at least one M.2. SSD, though older systems will likely rely on the SATA connections made possible with the 2.5-inch drives.