Over Provision
OP is when a certain percentage of an SSD’s free space has been allocated to help maximize the lifetime, endurance, and overall performance of the drive itself. It does so by
providing a permanent “swap space” for the drive’s controller to manage all the data traffic and storage for the drive.
Apart from being used to store SoC Controller firmware, optimized GC, and WL, OP is a space designated as Spare Block. After certain usage duration of SSD, these Spare Blocks result in Bad Block. The reserved Block in OP space can be swapped with LBB to alleviate the wear and loss during the NAND Flash life cycle, as well as maintain performance level of the SSD.
Typically, 7% of the SSDs capacity is reserved for OP. For a 3D TLC SSD, non-dense-write-in workload such that of a consumer PC, 7% OP space should be sufficient. Unless quality is of concern which results in more LBB, more OP space is required.
For enterprise applications that demands higher write-in applications and P/E frequency, SSSTC designs for larger OP space. This accommodates the temporary working space for GC while optimizing WL, to reduce NAND Flash P/E frequency, hence prolonging SSD usage.