Write Zeros Extremely Slow

Using an eSATA connection to a StarTech 6gbps dock to do an initial checkout of a SATA III 6gbps 4TB drive.

Running dlgdiag write zeros test. Task Manager (Windows 10 Pro x64) show drive active 90% of the time, ~470 ms response time and ~14Mbytes/sec write speed.

It has been running for 15 hours and has 65 hours left to go.

Does dlgdiag write a sector at a time, a track at a time or a cylinder at a time. IOW, how many sectors are overwritten with each I/O?

You are provided with two options when writing zeroes: Quick Erase and Full Erase.

Full Erase will fully wipe out the drive. This takes significantly longer (Many hours) in order to ensure complete data destruction. This process can take 9 hours for 32GB volumes, and is directly affected by hard drive size rather than interface.

However, if the hard drive in question has bad sectors the process can stall. This is why a health test is recommended before writing zeros.

This process can take 9 hours for 32GB volumes

That seems way too long. It implies 270 hours for a 1 TB drive.

Write zeros on the 4 TB drive has been running for well over two days and still has thirteen hours left. There is bug in the GUI. It is only showing a little over thirteen hours elapsed time even through the process has been running for over sixty hours.

It only takes a few hours to copy the contents of one full 4 TB drive to another one. So it should be possible to write zeroes over every sector – including the reserved ones – in a few hours. Apparently the Write Zeros process is doing more than just overwriting every sector on the drive with zeros.

I would like to know what it is doing.