The Trim command is designed to enable the operating system to notify the SSD which pages no longer contain valid data due to erases either by the user or operating system itself. During a delete operation, the OS will mark the sectors as free for new data and send a Trim command to the SSD to mark them as not containing valid data. After that the SSD knows not to preserve the contents of the block when writing a page, resulting in less write amplification with fewer writes to the flash, higher write speed, and increased drive life.
Different SSDs implement the Trim command somewhat differently, so performance can vary.
Trim irreversibly deletes the data it affects; recovery of accidentally deleted data, as can often be successful on magnetic drives, is not possible.A bit more on Trim.Trim has been defined as a non-queued command by the T13 subcommittee, and consequently incurs massive execution penalty if used carelessly, e.g., if sent after each filesystem delete command. The non-queued nature of the command requires the driver to first finish any operation, issue the trim command, then resume normal commands. Trim can take a lot of time to complete depending on the firmware in the SSD and may even trigger a garbage collection cycle. This penalty can be minimized in solutions that periodically do a batched trim, rather than trimming upon every file deletion, by scheduling such batch jobs for times when system utilization is minimal. This Trim shortcoming has been overcome in Serial ATA revision 3.1 with the introduction of the Queued Trim Command.
Trim on my SSD haven't been triggered for 21 days now so if I haven't erased some files they would be still there ?
SSDs are differently organized but HDDs are not so simple as it seams. There are two organizing systems on them too. Physical, as determined by FW and Logical as determined by OS and file system, data and it's position has to be recalculated every time a bit is read or written. Forensic programs work thru lo level format (FW ) to retrieve data not accessible by higher level (OS, file system, logical) formatting and file structure. Some data may also be moved to spare area (over-provisioning) that even mechanical HDD have and with thorough forensics can be at least partially retrieved. Data saving and retrieval services work on all those levels and are able to retrieve a lot of "lost" data even after multiple formattings and data damage. Takes a lot of time and effort though and that's why they are so expensive.
Study: Nearly Impossible to Delete Data on SSDs
As for accessing the data remnants following the HD-style methods, the authors said:
Figure 2 shows the FPGA-based hardware we built to extract remnants. It cost $1000 to build, but a simpler, microcontroller-based version would cost as little as $200, and would require only a moderate amount of technical skill to construct.
The paper was published in 2011. I haven't checked, but I would guess what they did is within the capabilities of commercial data recovery services.
Seems turning on bitlocker is far easier and more reliable. No-one can retrieve anything and you can always forget and destroy the keys if you feel the need to sanitise the drive.
Piling zeros on a SSD is not such a swift idea. It will produce a considerable slowdown for write operations. It is better to just delete the file and let Garbage Collection do it's job. For best results there it is good to halt the system in BIOS mode from time to time. Then the SSD has power but there is no write activity from the OS.
Don't know much about computers but if had a need for real security would have to find money for a system for like those at the link I guess.
I will probably just use the OS "delete" function ....
@WHS ........ what is the purpose in halting the systrem in BIOS mode ?? And how do you do it ?