On some SSD drives, once data is written the system will need to perform operations to free it. In addition, such an operation might cause your system to no longer work properly. Overall this would just wear out the SSD faster and result in a premature degradation of the drive's performance. If you were to erase the free disk space on an SSD, you would force the system to unnecessarily write not only to locations where data previously was stored, but also to fresh locations on the drive that have not yet been used. To combat this problem, SSD manufacturers implement techniques called 'wear leveling,' which distribute write operations through the available memory chips and extend the life of the drive by ensuring they all get used evenly. Solid-state technology has the benefit of being exceptionally fast however, the storage blocks in the NAND memory chips have a finite number of write operations that can be performed before they will no longer hold data reliably.

If you find this is the case with your system, and Disk Utility only shows the Erase Free Space option as being grayed out, then it is likely the reason is because your Mac is using an SSD as its primary storage device.

The option to erase free disk space might be disabled on newer Mac systems.Įven with using specialized equipment, such a procedure would only increase the slim possibility of data recovery, so using Disk Utility to erase free space does have its security benefits however, if you have purchased a new Mac system or upgraded your hard drive, then you may find Disk Utility no longer offers this as an option. Instead, any remote possibility of data recovery would require dissection of the drive and the use of specialized equipment that can detect residual magnetism. This option makes it nearly impossible for the drive's heads to be used for reading any residual magnetism patterns and recover files. This option writes zeros to the unused portions of the drive and overwrites any previously deleted files. To prevent this from happening, one option that Apple has offered in OS X is to erase the free disk space using Disk Utility. While this offers a quick way to delete files from the drive, the data is technically still intact on disk and thereby leaves open the possibility for recovery using special software. Conventionally when files are deleted from storage device, the system only removes their entries from the file system's directory, thereby flagging blocks containing the data as being free to use. Erasing free disk space is an easy (albeit not quick) way to help prevent the recovery of files you have erased from your system.

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