erasing free space on ssd

Because you never want to perform that on an SSD. It's meaningless for an SSD.

Kappy is quite correct.

An Apple-brand SSD uses built-in TRIM. This instantly erases free space after every deletion, for fastest performance and longest drive life.

EDIT: deleted files are gone forever, instantly.

No, I'm saying there is no need to use Erase Free Space on an SSD because it can damage the SSD.

SSD: an ssd has a built-in "eraser" that continously erases deleted files to prepare the disk for new writes. The Trim command is an OS command, that tells the SSD which files are dleted and can be earsed.

This is a continuous process, that is why you do not have to erase deleted files, it is also the cause that it is not very probable that you can recover deleted files.

Does this mean there’s no need to use the Finder’s Secure Empty Trash with a Retina SSD – and basic Empty Trash (with help from TRIM) achieves the same as what Secure Empty Trash does for a spinning disk?

If so, why wouldn't Secure Empty Trash be grayed out or omitted? If basic and secure empty trash are the same, why are there two menu items?

Thank you.

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Ref:

>> An Apple-brand SSD uses built-in TRIM. This instantly erases free space after every deletion, for fastest performance and longest drive life. EDIT: deleted files are gone forever, instantly.

>> SSD: an ssd has a built-in "eraser" that continously erases deleted files to prepare the disk for new writes. The Trim command is an OS command, that tells the SSD which files are dleted and can be earsed.

The Mac Pro may have multiple drives with different technologies installed. The Desktop TRASH is an illusion created for your convenience -- it actually consists of the combination of all Trashes on all mounted Drives and Servers.

There is a very subtle difference between TRIM-ing and Secure Erasing, which would not be lost on the mathematical thinkers who write Apple Operating System software.

Secure Erase actively over-writes the deleted blocks using Write commands and random data. Rotating drive data will have been physically destroyed by over-writing those data blocks, and the old data will be unreadable by any ordinary means. SSD data have will have been re-written to a new SuperBlock with Random data inserted in place of the blocks Securely Erased.

In an SSD drive, the old SuperBlock should be immediately cleared for re-write, or it may only be marked as deleted-and available.

The space taken up by the over-written data would not be freed. It MAY still be accessible to spies willing to dis-assemble the "drive" and read the individual memory chips to scavenge data, depending on controller design.

TRIM marks the individual SSD data blocks as surplus and unavailable to Read requests, but it does not necessarily physically re-write anything. Spies willing to dis-assemble the drive and read the individual memory chips may be able to read the TRIM-med data as well.

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Expert "regular" Users of rotating drives know that off-the-shelf software like the old Norton Utilities can read deleted data that has not been over-written.

Expert "regular" users consider an SSD that has been Erased as "data unavailable by ordinary means", and most feel that over-writing is un-necessary.

Military Users follow their approved procedure, whatever that may be. For SSDs, that sometimes involves grinding up the individual SSD chips in a drive formerly used to store secure data..

I would like to add to this: the SSD Garbage Collection (with or without Trim) means that deleted files are not erased immediately, but that the SSD is being erased (physically) continuously while having blocks of time free. That said, it will make reading a file possible until it is erased, which is not immediately (but rather soon, depending on how much is deleted at one time).

The afterthought is, that defragging works counterproductive on the SSD life, that recovering a deleted file only has a chance when starting the recovery immediately. This short period can be shortened by secure empty, but in reality secure empty does not have much advantage (unless you are under attack continuosly).

In a HD a delete means that the data still reside but that the "address" is gone, thus a file holds the recovery chance as long as the location is not overwritten. Here secure empty has immediate effect.

Lex