The kind of faultWhere the hardware is healthy and the fault is purely logical, two working days often covers it. Donor swaps and reassembling an array run longer, in this lab as in any other. Effort will not turn a slow read into a fast one.
Capacity and healthA sound 4TB disk keeps the imager busy for a matter of hours. A failing one, circling back over bad sectors, can tie it up for days. Those two facts set the timetable.
Finding a matching donorThe replacement part has to be an exact twin, matched on model, on family and on firmware generation, whether it is a head stack or a board. Priority work gets first choice of the stock here, but a rare drive takes as many days as the hunt takes, and no extra payment shortens that hunt.
What happened alreadyWhatever was attempted at home arrives with the drive: another power cycle, another download let loose on the disk, a rebuild driven through the warnings. Drives nobody has touched go back out fastest.