I have a USB pen drive (or whatever it's called in English or in any other language on earth). It has a volume of 2 gig. I store in it some documents and utilities worth less then 0.5 gig. It is extremely slow to write into or delete. Otherwise it works very well, responding fast, no corruptions, no errors, nothing.
It seems that there are files that are written quickly and others are terribly slow. If I try to delete the content it takes ages, so I usually format it (very quickly) and paste the content.
The computers runs USB 2.0 and is working perfectly. Moving the drive to another usb port doesn't help. When I connect a USB to IDE enclosure with a backup disk in it, it works very fast.