Is it faster a SSHD or a 15/10k RPM drive? I searched for a SSHD SATA 6Gb/s 15k RPM, but I cannot find one, I found only 7200/5400RPM drives, so I think I can only choose between this two options…
Get a Solid State Drive. It is faster,has better longevity and uses less power. The prices have dropped dramatically and makes no sense not to get a SSD today for the O.S. operation
NVMe drives are crazy fast, nothing can touch those. My laptop has one and it always amazes me how fast it is. Requires an M2 slot on the motherboard, but there's inexpensive PCIe expansion cards for them as well, has to be a 4x slot. They're not much more expensive then regular sata SSDs. With prices now even terrabyte SSDs are affordable. Can't see any reason to run a mechanical drive anymore.
Why are you guys telling him to buy an ssd? That's not related to what he said For a storage drive, the 10/15k RPM would be faster than a hybrid drive. Hybrid drives only have small caches and they will be populated with really small files. Those files are common on OS installations, not on storage drives. Unless you are accessing the same files over and over again, a fast mechanical hard drive is the way to go.
There are sas / sata adapters are available but i wouldn't bother, the ones i found said the mobo must have sas support which kinda makes the adapter sound pointless... if your just planning on storing data, just go for a sshd or hdd.