I have a 4TB external HD which I use for timemachine backups. At the end of a backup I eject the disk by "right clicking" its icon and selecting eject. The icon disappears -which I have always assumed means that it is safe to disconnect it. However, I have found that it continues to "chunter" (disk head movement) for over a minute.
What is it doing?
When is it OK to disconnect?
Thanks
Richard
Time Machine is a very complex database keeping track of old files and their recent revisions. To maintain space when necessary, it will delete old files providing there is a newer version. The disc is probably tidying up after it has copied all that's necessary so is best left attached until you're sure it's no longer working - hence my initial flippant comment.
With a desktop machine, I'd advise leaving it permanently connected unless you have a specific reason for not doing so. I appreciate that with a laptop this is not practical.
Richard I 