If running windows, which version?
What app is used to “copy”? copy or xcopy… Read long ago that xcopy also copies subdirectories but it reads an entire file before it does the writes, not sure if still true. Copy is ok but not for lots of files.
Also, does the destination have lots of data already or fragmented so that the copy has to dig for the empty spaces? Is the copying done with specifications? e.g. updated date/time, doesn’t exist.
If running vista or win7, try “robocopy”; it is comes with vista & win7 even if it is not documented & supposed to be better than xcopy & faster; do “robocopy /?” for help/howto.
Or try “richcopy” free from microsoft & uses gui & may be better than robocopy for you; robocopy is command line oriented. Richcopy also uses 3 threads default for copy & can be adjusted upwards but read that 3 was “optimal” in testing it; richcopy default will get the copying done for 3 files at a time.
However, another kicker is that copying to/from a usb 2 harddrive will be quite slow; then also there may be a long delay in starting the copy process if either drive was in “green” mode (sleep) & I’ve found that the MBL is sometimes “half asleep”. The wait times is also calculated in how fast the copying is being done.
I have over 320 gigs of files & my copying/backups to an usb3 drive is getting “slower” due to the checking for “not exist” & date/time update & waits for both drives to wake up from “green” mode; don’t think any drives are not green anymore to “save” power consumption.