Why do I need to certify a SSD with 2 or more passes?

Some of the controllers used on SSDs (Solid State Disks) use data compression to minimize the amount of data they have to write to flash memory. This allows them to minimize the wear on the flash memory and to attain much higher write performance when tested using benchmarking applications. (Most benchmark applications write blocks of zeros when testing the write speed of a disk).

The disk certify function in SoftRAID was written with these data compression SSD controllers in mind. Every pass of the disk certify function, except the last one, will write out a non-compressible random data pattern. This ensures that SoftRAID tests as many of the locations in the memory chips as possible.