I have an older computer. It only has SATA II ports, but it does at least have USB 3.0. I’m not a gamer, so it’s fine. Anyway, leaving out the long and boring back story, here are results I got that I don’t understand.
1 drive speed X.
2 drives, Windows striped volume - speed 2X.
2 drives in an external RAID enclosure. It has SATA III ports and can connect to a computer via USB 3.0. Doing that and setting it to RAID 0 gets me speed X.
SATA II drives in a Windows RAID 0 are faster than connecting them by USB 3.0. why?
Actually, what I meant to say is that external USB 3.0 RAID 0 is the same speed as a single internal SATA II drive.
Actually, USB3’s top speed of 5Gbps is faster than SATA2’s 3Gbps but drives don’t usually hit their maximums anyway.
What I think you’re missing that you’re comparing using two SATA2 cables connected to two drives vs a single USB3 cable connected to two drives. With two SATA2 cables you’re getting a maximum of 6Gbps vs the single USB3 cable’s max of 5Gbps.
There’s more that goes into RAID drive speeds than that (latency, RAID controller speed, etc) but all told I’d expect the two sata2 drives to be a little faster than the external RAID0 enclosure using USB3.
How do you know your speed before was twice as fast? How are you calculating your speed?
CrystalDiskMark 6.
Looks like they’re up to 8 now.
Your device might use USB3 in order to get 900 mA on the 5 volt power, which is better than USB 2’s 500 mA.
Huh. I woundn’t expect it to be twice as slow but a drive connected with USB3 will have higher latency (a bad thing) compared to a drive connected with SATAII.
It can make a big difference for small, frequent reads & writes, less so for large file transfers. Maybe that’s why.