How to copy a good RAID1 HHD to new HDD outside/with WIN10 machine

Boo

I have a Zyxel NSA221 NAS device that still chugs along after nearly 10 years.
I acquire used Enterprise server HDDs and swap out 2TB drives from time to time (this is a RAID1 configuration) and it takes basically 2 weeks to recover a ~1.5 TB volume and often one of the drive bays will go "red" at the end of the process. I always check the S.M.A.R.T. info and do a surface scan of these drives (amazingly, almost all the drives I find have not a single bad sector on them). Sometimes I'll just change the disks in the drive bays (1-2, 2-1) and the RAID1 will rebuild/recover without error. I'm attempting to perform a disk copy/clone with a Win10 machine and see what happens. Surely this will not take 2 weeks. Anyone done this? Need to pretend to accomplish something during these COVID-19 days (mainly so my wife doesn't strangle me in my sleep).  

Mijzelf

I suppose you want to be able to use the clone in the NAS? In that case search for a bit-by-bit clone program.

it takes basically 2 weeks to recover a ~1.5 TB volume

Something is wrong. That is around 1.2MB/sec. I estimate it should do around 30MB/sec, that is 14 hours. That is, if you mean re-adding redundancy, aka 'syncing' the disks. That is no more than a bitwise copy of the raid member content from one disk to another.

Sometimes I'll just change the disks in the drive bays (1-2, 2-1) and the RAID1 will rebuild/recover without error.

That is expected behavior. The raidmember has a header which tells which role the member has in the array. So you can shuffle the disks, the raidmanager won't notice, or case. That is also true for raid5/6.