Much faster than network, much easier than an SSD
128GB USB Thumb Drive
I purchased a Silicon Power 128GB USB 3 thumb drive that I use to store images on in imaging computer. As part of my sequence in NINA, one of the last steps is to fire off a script that copies the imaging session to the thumb drive if it's connected. This way, I don't have to copy stuff over a slow and sometimes unstead Wifi link (though my gl.Inet Opal is a wonderful piece of gear). The last step is a safe eject, and the drive is ready to be manually moved via SneakerNet to my big computer for processing. It says 128GB on the outside, but there's only about 117GB usable space. That's enough to hold about 2400 subs from my ZWO ASI2600MC camera, and even if I take 10 second subs (the shortest I take are typically 30 seconds), that's more than enough for one night's imaging, and sometimes multiple nights.
Yes, I could put an SSD or other external hard drive on that measures storage in terabytes, but they also consume more power. A USB thumb drive is about the lowest watt/GB route you can take, and 128GB seems to be the best price/GB as well. Anything smaller and I may not be able to get one night on there, and anything bigger and I'm just paying for space I don't need.