Disk Utility Zero Out Data option

I read that it can be good to write zeros to all sectors of a new external disk right away.

That is not necessary at all and there is no benefit to doing that.

With all due respect to Roam, the Zero Once does stand a chance of writing out bad Sectors, not usually needed on a new drive, but if you have the time, may as well do it. 🙂

For those who may have to reformat a new hard disk drive, one may as
well take a little more time and have another cup or three of coffee...
and let the computer utility write zeros in one pass; maybe even twice.

Some new computers, especially some sold in a few geek guy stores,
had their bogus utilities installed; an additional $40. charged on each.
If you liked it or not. Same computer elsewhere, -40 but no geek app.
And their choice caused some people issues with their new non-PC.

The best avenue was to boot from OS X install disc & choose secure
erase, and totally over-write the new computer's corrupted software.
And choose the install option after disk utility ran, and start over right.
With the correct partition map, reformat and a new full install.

New and planned replacement upgrade hard disk drives can be put
into an external HDD enclosure ahead of schedule, if not a tower;
and ready them for later use; even test them thoroughly if desired.
Especially if the computer the HDD is intended for, is hard to open.

The main consideration, other than product testing, or in feeling all
warm and techie inside, is the amount of time this sort of thing takes.
The impatient won't hold up under the strain of loftier commitments.

Oh well... coffee is cheaper if you get yours from Kona directly.
Good luck & happy computing! 🙂

Erasing a new external hard drive is a good idea. If you have (and use) an intel Mac, you may want to check the partition map scheme. It would be best if it had the GUID Partition Table. If it does not use this partition map scheme, you will not run into any problems, it's just that you can't boot from it.

Erasing a new external hard drive is a good idea.

Some people may think so and they are entitled to their opinion. My opinion is not that it is a bad idea, rather it is pointless.

As you've sen in other replies, it can be argued both ways. On the "don't" side is also this kind of thing puts a bit of stress on the drive because of the sustained activity, especially with today's large drives.

Some third party utilities such as TechTool and SpeedTools have surface scan utilities. I don't know the details of how these work and if they are any friendlier than writing zeros.

it seemed to be implied in the responses that the Zero Out Data option does in fact write zeros to the entire disk, not just over data that was on the disk...

Yes.

I just ran TechTool on an iMac 1.8 that was acting wonky and when I did the surface scan, sure enough, there were four bad blocks, with at least two of the four in system-related folders. I am now Zeroing out the drive to map the bad blocks, but according the system, it will take 2 days and 14 hours on a 150G drive.

Does this sound reasonable or is something going on here?

Does this sound reasonable or is something going on here?

It can take a long time depending on CPU & drive speed., but the estimated time may be very off the mark.

Very off the mark as in reported inaccurately or very off the mark as in start the process over?

Just the report is a ballpark figure... a very big ballpark, could be half or twice that, generally no need to restart it, but if the drive is really having problems it may never finish or lose contact with the drive.

For what it's worth, SMART says the drive is OK and I was planning on letting it run over the weekend anyway (it's at the office)

The estimated time is usually off at the start of a drive repair, bad block scan, etc. It should be only about 24 hours. If not, its right, and there is no need for you to restart the process.

I started it Friday afternoon. It's still chugging along and now says 1 day, 12 hours, down form the 2 days, x hours it said Friday.

Since I know there are four bad blocks (via TechTool), but SMART says it's OK otherwise, I will simply let it do its thing until it's done.