disk utility erase ext drive first w/o more secure then with 3 pass?

Yes you can - it should get rid of the data fragments floating around

Be sure you only "secure erase" HDs. When you "secure erase" SSDs you can clog the delete/erase path to the point the SSD may be unusable again.

Radium88 wrote:

hi all---

will doing this out of step like i did still result in erasing the disk the way that i wanted to? ie 3 pass?

Yes, you will still get the 3 pass result that you desire.

The default erase overwrites the directory and finishes in one minute. The data blocks of your files (on a magnetic disk, not an SSD) are possibly recoverable, but there is no directory and no filenames.

The first click off the default overwrites the data blocks with Zeroes. Your data blocks are actively over-written, and there is no way to re-create even a portion of the data without dis-assembling the drive in a clean room and reading the data with special equipment. This is adequate for all except nuclear secrets, where spies would actually do that disassembly if they thought they could get a portion of your secrets.

Three passes takes three times as long, and provides almost no more protection from re-creating your data than one pass with Zeroes.

Military requires more like the 35-pass erase, and the drive might die before that completes.

You can re-erase the drive as many times as you like.

just clicking erase is essentially safe enough to not worry about any data recovery applications harvesting data from the drive?

Just clicking erase (done in one minute) gets rid of the filenames and the locations of files. But what Data Recovery Applications claim to do is exactly 'recover the un-overwitten data blocks that remain'.

I advocate using security erase, one pass of Zeroes (one click off the default). This actively overwrites al the data blocks with zeroes, but does not take three days to do it. What is left on the drive is still very, very difficult to salvage, and no data recovery Applications alone can touch it.

The incremental security provided by more passes of overwrite instead of just one was never worth it to me. Three passes takes three afternoons instead of one.

If you have it running, leave it running. Cancelling sometimes causes problems. More does not hurt, it just takes longer.

Default erase writes over the Directory (only). Any other security options write over the data blocks as well as the directory, one pass or multiple passes. It is all cumulative.

You are talking about flying an active electromagnet over the magnetic regions on the disk platter. The data changes to something other than what it was before. Everything you do is destructive, there is no "Undo", you cannot go back to the way it was.

Physicists would argue that there may be some small residual of the previous magnetic pattern after overwriting. But you would have to use very expensive special equipment to get even a small portion of that. That is what you could salvage in the NSA labs, but not with just Utilities at the desktop.