Time Machine configured to back up an external hard drive - is this normal?

hi everyone,

hope right forum question. sorry if it's not. , apologize if has been answered. did try searching around, didn't find anything... wasn't sure of search either.

have time capsule set time machine drive. have configured both internal hard drive on laptop external drive keep hooked laptop of time.

realized in past few weeks time eject , reconnect external hard drive laptop, time machine tries entire contents of external drive again - it's 400+ gigs , takes long time.

i'm wondering if expected behavior. shouldn't time machine has changed on hard drive, instead of whole thing every time? idea why trying entire hard drive again whenever plug in laptop? , there way stop doing that?

appreciated.

 

same question re: long time

have similar issues. using goflex hard drive , takes forever .... out there advice both?

 

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