Secure erase files
All blocks are erased when this is done, resulting in a pristine drive. Secure Erase instructs the drive to wipe all stored data, including data which may remain in the over-provisioned NAND regions. The only way to truly erase data on an SSD is to use the ATA Secure Erase commands. Writing and erasing NAND pages and blocks and garbage collection is explained in white paper 04.
#Secure erase files series
Samsung's SSD white paper series provides a thorough explanation of the inner workings of SSDs.
#Secure erase files pro
This is why high-end enterprise SSDs such as the Samsung SSD 845DC PRO come in sizes like 200 GB and 400 GB even though the drive actually contains closer to 256 or 512 GB of NAND inside, respectively. Added over-provisioning helps mitigate write amplification by providing more spare space to rewrite data and erase old blocks. Under extreme conditions where the SSD is being asked to write data faster than it can erase old blocks (common in write-heavy datacenter workloads), it may be forced to rewrite the data in one block into another block, then erase the old block immediately to make way for new data, before it has had a chance to perform garbage collection.įorced rewriting of a block is less than ideal because it degrades performance and contributes to write amplification, where more data is written to the underlying NAND than the actual amount the drive is instructed to write. Efficient wear leveling can only be achieved if there is a certain amount of space ( over-provisioning) that is reserved to allow for efficient garbage collection as required even if the drive is nearly full.
![secure erase files secure erase files](https://cdn.macpaw.com/uploads/images/secure_erase_files.jpg)
In all cases, however, SSDs must spread writes out over the entire drive to avoid placing undue wear on any single block in order to avoid premature failure of the drive, through a process called wear leveling.
![secure erase files secure erase files](https://www.howtogeek.com/wp-content/uploads/2013/09/physically-destroy-hard-drive.jpg)
Many of today's consumer-grade SSDs use 19-21nm NAND where each block is good for about 3,000 cycles before becoming unusable, although enterprise SSDs and several high-end consumer SSDs that use more durable types of NAND are commercially available.
#Secure erase files free
SSDs try to spread writes evenly over the NAND to avoid premature failure, a process which relies on the free space available to the drive.Įach NAND block can only sustain a finite number of write/erase cycles.
![secure erase files secure erase files](https://www.rawinfopages.com/mac/sites/default/files/sites/default/files/img20/secure-erase-5.png)
The SSD is then free to garbage-collect those unused blocks. In order for the SSD to know which blocks can be erased, the operating system must tell it which blocks no longer contain valid data. This cleanup process is called garbage collection. At a more appropriate time, ideally when the drive is idle and all pages in a block are marked invalid, the SSD can erase blocks that are no longer in use. This means that whenever data is rewritten, the SSD must mark the data in the affected pages invalid and rewrite it elsewhere, possibly in a different block. Source – Courtesy Music Sorter at Wikipedia, CC BY-SA 3.0Įach page may be written to individually, but pages cannot be rewritten until erased, and erasing can only be done in whole blocks.
![secure erase files secure erase files](https://www.idiskhome.com/resource/images/secure-eraser.png)
The following diagram assumes 256 KB blocks, but the concept is the same regardless of the block size. Most modern SSDs uses NAND with blocks of 128 pages for a block size of 512 KB, although some drives, especially older ones, may use 256 KB or smaller blocks.