I read reviews here about 40 Mb / s for recording, bought it and it turned out to be partly true. When you start writing large files of several gigabytes (movies), the speed is immediately 40Mb / s, then after a couple of minutes 30Mb / s after 3 minutes the flash drive "chokes" and goes to a "cruising" speed of 25 Mb / s (ntfs and exFAT are the same) and with this constant speed is already adding everything else. This speed result for files 10,20,40,80 and 100 GB. With small files (photos, music), things are even worse on exFAT 20Mb / s, ntfs 17Mb / s, i. E. a flash drive will be written for about 2 hours and these promised 40 Mb / s can only be achieved when writing one file at a time of about 1 GB, that is, writing one file per minute. Then the flash drive "gets tired" and writes almost 2 times slower. The next file again starts briskly at 40 Mb/s and "gets tired" after a minute.
It is not suitable for recording digital TV, the TV set "says" a "slow device", there is a mandatory streaming recording speed of 30 mb / s. (I tried other flash drives where the established speed is from 30 mb / s, recording from the TV set is normal). There are also 128 GB flash drives for comparison and they have a cruising (established) speed of 40 and 50 mb / s, and an external usb hard drive has 80 mb / s (in case you think that I have a connector or a slow computer). About formatting:
ExFAT is a little faster, but still this format is not as versatile as ntfs. exFAT cannot be viewed on Windows XP, on many TVs, media players. And such a volume of a flash drive provides for cases sometimes to watch a movie from a friend on a TV set with beer or at the dacha on an old computer (with XP), turn on Mouzon, and exFAT seems to be with you and a lot of everything is recorded, but you can’t turn it on.