Very slow, "essentially new" external hdd

Disk Utility is the graphical user interface version of working with UNIX commands to perform disk management functions. Overwriting a drive, especially one 1.5 TB is going to take time, every bit-size space has to be written to by that procedure.

If the drive was formatted using Disk Utility as Mac OS X Extended(Journaled) any speed limits should be related to the hardware itself. Drive speed is an important factor, is it a 5400 rpm drive? That will be significantly slower that a 7200 rpm drive. How are you interfacing the drive? FireWire 800 is faster than FireWire 400, faster than USB 2...none of which can approach the speed when internal on a SATA bus.

it is several years old

How old is "several"? If all it has is a USB version 1 connection, it's going to be incredibly slow due to the connection. What model is it?

I have managed to repartition/reformat, with both gparted and Disk Uility (after unmounting

using diskutility) - the latter into Mac OS Extended, GUID partition.

The WD came with windows on it, as the boot drive of the pc mentioned above. I wonder

if I still haven't managed to remove all of the low level formatting on the as-purchased disk/pc.

(I don't really know what that means, and repeat what I have seen on the web.)

Doesn't matter in the least what used to be on it now that you've completely repartitioned and reformatted the drive.

Now I am trying to write zeros over the disk, hopefully over the entire media.

Unless you're trying to make sensitive information difficult, or impossible to recover, that's a complete waste of time. It only succeeds in wearing out the drive faster.

I have read this can work to get rid of slow, unmountable external hdd issues.

Whoever wrote that isn't very bright. It won't change a thing in that regard.

But Disk Utilitiy reports that it will take almost 4 days to write zeros. I would have expected maybe an hour or two.

It's 1.5 TB. Yes, it will take a silly long time to finish.

It has taken 10 minutes, and the cancellation process has even succeeded!

Good! Don't restart it.

There does seem to be a difference between Disk Utility and diskutility, in terms of "effectiveness".

Not sure what you mean there. There is only one Disk Utility in OS X. It's in the /Applications/Utilities folder.

from building PC's since 1995 the words "high end" and "acer" do not go together in a sentence under any circumstances. Acer is notorious for low-balling parts to keep cost down and gaming machines were not their forte.

platter based 5400 RPM are lower speed, lower heat drives generally found in entry and lower end laptops to keep cost down at the expense of performance. If you are connecting through a 3rd party connector or enclosure I would test the drive on another system that can remove those from the equation and see if it displays the level of slowness you're describing.

Formatting uses space itself, plus the partition table information so a 1.5 TB drive never has that amount of space available.

While it is possible that the drive is bad, I would start over with it and format/partition again. And by the way, you cannot low-level partition a modern drive, doing so is a sure way to make the drive unusable. Partitioning and formatting rewrites the boot sector, sector 0, which is what low level formatting erases.

Try starting over on the drive to be sure it is formatted correctly. Be sure you use Mac OS X Extended (Journaled), not Case Sensitive Journaled as that is a special format for UNIX executable file compatibility and can slow things down under normal file use.

Thank you for the extra info.

As JimmyCMPIT has already noted, a 5400 drive is considered slow to start with. USB 2 speeds aren't all that bad, but still much slower than if the drive were directly attached to an SATA cable or slot to the system board.

A cheap bridge board in the external housing could also be the cause of the slow access (a bridge board controls the flow of data between the drive's connector and the external ports on the housing).

But anyway, don't start any other type of zero erase. It won't help or change anything. Just use Disk Utility from OS X's interface to repartition the drive as GUID, and format it as Mac OS Extended (Journaled). It will go as fast as it's going to go based on the limitations of a 5400 rpm drive and the external housing it's in.

building PC's does not mean you get good parts or even new parts sometimes. You gotta do with what you got.

Jumpers should not be part of the equation except for a few very non standard scenarios outside of what your doing.

A WDC Green 1.5 I think should have NO jumpers for default use but you might want to verify that with the model # on their support page.

You can get a rough figure for drive write speed by looking at Activity Monitor.

Select the disk tab & look at the graph at the bottom.

Repartition your disk (without zeroing). Copy a large file from your Mac to the disk & view the rate. It does include all other disks so it is just a guide, however you can quickly see if the disk can write at USB 2 speeds. Copy test files over a few GB to overcome drive caching.

In my testing on OS X…

USB 2 is around 20-25MB/s

USB 1 is around 2MB/s

A quick calculation suggests your estimate was for a disk running around 4MB/s…

http://www.wolframalpha.com/input/?i=1.5TB+at+4MB%2Fs

Personally I'd triple check that USB2 is being used (System Information should state it).

Writing zeros to a disk is supposed to trigger it to map any blocks that are damaged. It may help but it seems to me that you have a disk, drive case or USB port that is under performing.

WD Green disks have always been slow, I'm not sure you want to trust this one too much.