Ok, understood, but lets speak with numbers. Samsung Evo 250GB when formated is about 233GB and in this number you can put the over-provisioning space, Samsung Pro 840 256GB is 238GB formatted and in this space you can set the over-provisioning. Samsung 840 Pro 512 is 476GB formated and in this space you can set overprovisionig.
Samsung 512Pro and Sandisk Extreme Pro 480 have the same total amount of NAND’s 512 summary.
So, a Sandisk formated must be about 477GB but finally is 477Gb unformatted. The other space i think is the area of spare blocks. The difference between the 447GB (full formated without free space) and the 478GB who must be formatted is the over-provisioning space? or not?
I think Sandisk to prevent problems, special with a 10 years guarantee (as and other manufacturers) have make a replacement area with block’s who isn’t visible to end user.
I don’t know if this area is used as a spare blocks or to over-provisioning, overprovisioning and spare blocks are to total different things.
The over-provisioning procedure use TRIM commands and working through the OS. If the OS can’t find free space (unallocated-empty) in an ssd can’t run the overprovisioning procedure properly. Overprovisioning (OP) procedure keep ssd’s run healthy, optimizes performance, extend lifespan.
Spare blocks is replacement blocks in an ssd.
I believe some more information from Sandisk are necessary.
And i don’t believe is counted strange, just count the total capacity if you leave the spare blocks.
So, anyone can tell for sure if this area of 30GB of invisible spare blocks are used for something else like the OP procedure?
May be Sandisk can have some special commands for this invisible area, may be, but as anyone can see in some reviews if you leave a good OP area (unallocated space-non formatted about 20%) the performance increase and extend the lifespan of ssd.
And Deponia where you can see this blocks? Sandisk Extreme Pro 480 is 477GB unformatted and 447 formatted, you can imagine this blocks because the number of NAND’s and the conversion to GB’s. 512 total amount of NAND’s will be 480GB formated but is 447GB formated.