Having to use any kind of a USB to whatever adapter is a bad idea. They tend to require a bit of power off the line, and with the substandard availability of power to USB 3.0 clients on any model of Pi, that is just tempting fate.
Further, it cannot possibly provide any advantage in terms of performance over a straight USB connection, for hopefully obvious reasons (it's still going through the USB hub, which is the bottleneck in this context), and what's more, any overhead for protocol translation -- although this is unlikely to be much -- is going to detract from that.
It really only makes sense if you already have a drive you want to use and economics are a factor so you'd rather spend $20 on a cable/adapter than $100 on a new drive. If you are considering paying for both just to get something that is more prone to problems, don't.
do i need to use Sata memory and a sata to usb adaptor if i want ssd with my Pi?
There are oodles of pure USB 3.0 SSDs on the market, so no, you do not. There is not really such a thing as "sata memory", BTW, it is just a type of connection.1
So to clarify some things here:
- M.2 is a form factor for internally mounted SSD drives. You probably do not want this, since the drive will not be internally mounted -- unless you buy an enclosure for it, which is arguably pointless since again, it is going to be attached to a USB port, hence you might as well just get a USB 3.0 drive that doesn't have to be mounted in anything.
- "I'm confused between nvme vs sata; are they both 'protocols' as opposed to physical buses" -> They are both ways to physically connect a drive to a computer, however, NVMe is not considered a bus, it's a protocol for use with a PCIe bus and such drives attach
to PCIe slots. SATA describes a physical bus and uses it's own type of connector.
You want none of the above. You will be best served with a USB 3.0 SSD. If this is a portable type and you are not connecting much else to the Pi, it can probably be powered through the USB, whereas a SATA or NVMe drive will require its own power (probably via an enclosure such as mentioned above).
- I'm totally appalled that I managed to find this article near the top of an online search on the topic, claiming to be comparing SATA drives to SSDs (and HDDs) and that SATA is some kind of parallel option, ie., that there are SATA drives that are neither SSDs nor HDDs, that they have "moving parts", and all that from a company that purports to sell such things and even worse, "has specialized in providing secure, innovative technology product and service solutions to the federal government across the U.S. and worldwide since 1978". Yikes!! If there is any doubt in your mind, search/shop online for "SATA SSD drives" and read the SATA article in wikipedia. Unbelievable.
