Why does deleted data stay on a HDD once written, waiting to be overwritten, as opposed to being removed when requesting deletion?

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Why does deleted data stay on a HDD once written, waiting to be overwritten, as opposed to being removed when requesting deletion?

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Anonymous 0 Comments

Efficiency. If there’s a paper document that you don’t need, you move it to the trash. You have to do extra work to run it through the shredder.

Anonymous 0 Comments

Imagine your data is a library. Each book (file) has an index card that the librarian can use to quickly find out the location of that book. When the book is to be forgotten, the librarian can just get the index card, and throw it away (or reuse it for another book). The book itself hasn’t gone, but the reference to it has gone. Throwing away the card is quick and easy and doesn’t require the librarian to walk a distance to retrieve the book. If a new book needs to use the same shelf apace as an existing deleted one, the librarian can remove the old book then. Same with erasing data. Just mark the index as empty and reuse the space when required.

Anonymous 0 Comments

Forgetting where it is on the drive is just as good as deleting it for almost all applications. Why spend system resources if you don’t have to?

Anonymous 0 Comments

Imagine you have really bad ADHD.
You have all the things you use on display.
If you put something in the cupboard you will forget it exists.
You could also throw it in the trash but that will take longer.

Anonymous 0 Comments

Fully deleting a file is just writing a “blank” file over it.

Its just so much quicker to forget the file exists. So that most of the action from a drive is writing actual useful data and not useless blank data.

Anonymous 0 Comments

Imagine laying out dominoes to represent information. Literally those *black little wooden rectangles*.

Your disk has a Table of Content, which tells it: “*hey, dominoes number 35 to 79 contain THIS type of information*”.

When you “*delete*” the file, you tell the TOC: “*Hey, forget about dominoes 35 to 79*”.

So it shows them as being available for storing new information. But these dominoes are still in place. If someone looked at them, they might be able to make up the information.

This is how data recovery works. Even if your TOC is lost, it’s still possible to try to make sense of the information. But it’s probably like a million piece puzzle.

When you *overwrite* your disk, you actually mix the dominoes up and the information is no longer there to be seen.

Anonymous 0 Comments

Computers have something called pointers, it basically points to where something is stored. Kinda like a file shortcut.

To read a file from the hardrive, the reader needs to be pointed to the file by a pointer.

If any part of the hard-drive isn’t being pointed to, its considered empty.

So if you have a certain file on a hard drive, and want to delete it to recover the memory, you could take time overwriting all parts of the drive to have 0s, or you can simply delete the pointer to that part of the drive, skipping the partially lengthy process.

Next tome you want to use that space, the system will see it as empty and just overwrite it.

If you later want to recover that data though, its still written there and potentially accessible.

If you really want to delete things securely though, you need to overwrite garbage values over it multiple times, as they do leave partial trace of their old states, but that’s really only for super top secret stuff, at which point you might as well destroy the drive afterwards just in case.

Anonymous 0 Comments

Think of magnetically written data as paint on your wall. If you no longer want a blue bedroom wall, can you remove the blue? It’s not quite impossible, I guess you could use paint thinner until all the blue is gone, but there’s no reasonable way of removing the color: all you can really do is paint over it.

Magnetically written data is effectively the same: you can’t really delete it, you can only write more data over it. Just like you could paint the wall white, you could make the new data all zeroes; but you’re still painting over it, not deleting.

So as deleting isn’t an option (for magnetic storage; optical and Flash work differently), you’re left with either simply overwriting later or overwriting now and then overwriting again later. The second takes extra time and adds wear and tear to your disk, for generally no advantage (if you need data security, disk encryption is a much better solution anyway).

Anonymous 0 Comments

When you write something to a new drive, the data is written over that section of 0s. When deleting, it is faster to just tell the computer that it can write new data to that section without having to overwrite everything with 0s and start from a blank slate.
Instead of having to go through and ensure every bit of data is reverted to a 0, the computer just confirms new data when it is overwritten later on, making sure the 0s and 1s are where they should be.

Anonymous 0 Comments

Data isn’t deleted when you delete it, it’s marked as a writable block, and remains in tact until the hard drive uses that block for new data, which on traditional HDDs is pretty random actually. This is why you should scrub drives before selling or disposal and the scrubbing software writes junk data over all the ’empty’ space.