[SOLVED] Wiping HDDs ?

[The Original Ralph]

Just curious, i'm reorganizing eight 4TB HDDs, compressing video files and moving to another HDD

do HDDs wipe the track when writing new data or does it serve to wipe the entire disk first? I just wiped one 4TB HDD and it's actually still "wiping", 4 hours later and about 75% complete

 

[Solandri]

When you delete a file from a HDD, the first byte of the file is changed to say the file has been deleted and the space it used to occupy can be used for other files. The file data actually still remains. If the data on the HDD has not been overwritten by other files, it's possible to undelete the file by changing that first byte (typically it's the first character of the filename).

For most computer use, this is good enough. There's no point wasting time erasing the actual data of the file, when it will be erased when you write new data to those sectors of the HDD by writing a new file.

But for security purposes, if you need to be certain that the original file data has been scrubbed, you can instruct the drive to erase all the space the file used to occupy. That's what you're doing when you wipe the drive or do a full format on it. This will take a lot of time (4 hours for 75% is actually pretty good; often it can take 10-20 hours on larger drives).

If you don't need to completely wipe the file, then just deleting it is good enough. Or if setting up a new disk, a quickformat is sufficient.

Note: None of this applies to SSDs. They work in a completely different way.

 

[atomicWAR]

Depends how you format it. A quick format should just take a few minutes, a full format can take days depending on the drive size...read this for more.

https://support.wdc.com/knowledgebase/answer.aspx?ID=1217&lang=en

A quick format just deletes the partition where a full format scans each sector for bad spots which is why it takes so long.

 

[The Original Ralph]

When you delete a file from a HDD, the first byte of the file is changed to say the file has been deleted and the space it used to occupy can be used for other files. The file data actually still remains. If the data on the HDD has not been overwritten by other files, it's possible to undelete the file by changing that first byte (typically it's the first character of the filename).

For most computer use, this is good enough. There's no point wasting time erasing the actual data of the file, when it will be erased when you write new data to those sectors of the HDD by writing a new file.

But for security purposes, if you need to be certain that the original file data has been scrubbed, you can instruct the drive to erase all the space the file used to occupy. That's what you're doing when you wipe the drive or do a full format on it. This will take a lot of time (4 hours for 75% is actually pretty good; often it can take 10-20 hours on larger drives).

If you don't need to completely wipe the file, then just deleting it is good enough. Or if setting up a new disk, a quickformat is sufficient.

Note: None of this applies to SSDs. They work in a completely different way.

thanks - it's not for security, was just worried about artifacts from previous video files showing up on the screen. I learned the hard way on SSDs to wipe before writing to them. I just didn't know if HDDs were like the reel to reel tape recorders where there was one head ahead of the writing (or recording head) that wiped the tape automatically

 

[USAFRet]

If you're keeping the drive for your own use, a quick format is good enough. The file headers are removed, and the associated blocks of that "file" are simply space to be reused. And it will eventually get overwritten.

This isn't like analog tape, where previous information may still be there and usable.