[SOLVED] How does one overprovision an NVMe drive?

[wcndave]

My Samsung SSDs can be over provisioned using samsung magician, however I can't see how to do that for other brands, eg Sabrent. Any ideas? Or is it somehow baked in?

 

[MasterMadBones]

Most SSD manufacturers don't allow you to change this as far as I know, and not all SSDs have static overprovisioning. However, most modern SSDs use a combination of static and dynamic overprovisioning, and it all happens automatically depending on how much space has been used. You roughly calculate the amount of statically provisioned space by subtracting the advertised capacity from the nearest power of 2, for example a 500GB drive likely has 512GB worth of NAND, but 12GB is statically provisioned.

The dynamically provisioned space is roughly a third of the remaining capacity on TLC drives, and a quarter on QLC drives.

 

[wcndave]

So what you're saying, is that there's nothing to do. Although with Samsung, I went in to Magician and set 10% provision, in order to extend the lifetime of the drive, other manufacturers just set some sensible limit.

 

[MasterMadBones]

Although overprovisioning is part of extending the drive's lifetime, its main use today is to improve performance by using that space as faster SLC memory (which also wears more slowly). SSD controllers have very sophisticated algorithms to reduce wear on the cells as much as possible.

Provisioning of space for an extended lifetime is a statistical problem. If all cells in a drive take the exact same amount of time (or write cycles) to go bad and all are used equally, it's pointless to reserve any number of cells for replacement of bad cells, as you would just end up writing to the same cells more often. However, each cell is slightly different and not all of them are used to the same degree. Cells that die unusually quickly may be replaced, but by the time that a drive needs 10% of its total capacity to replace bad cells, it's already dying fast, because good wear-leveling algorithms make sure that all cells die more or less at the same time.