Quote Originally Posted by Ao1 View Post
Those timings are at the NAND level. If a block is not clean, i.e. it contains a small of amount of valid data, that data has to be relocated before the block is erased, which adds time to the operation....

A secure erase can be executed in under ~ 2 seconds,...
In general it is true that GC may need to relocate some flash pages before a block can be erased. But in the specific case of ASU endurance test on the Samsung 470, I think that there is little relocation needed. For two reasons -- the amount of random writes are relatively small compared to sequential writes, and it is set to keep 12GiB free. With few random writes, 12GiB free, and TRIM, the GC just does not have much work to do.

As for SE in 2sec, I think that is highly dependent on the SSD. I've had a SE take more than 30sec (I think it was an Intel G1). And I've seen references to it taking a minute or two. Some SSDs have built-in encryption, so all it has to do is generate a new encryption key and mark all pages invalid in the index, so that could be done very quickly. But for SSDs without encryption, it is not "secure" to just mark all the pages as invalid -- it needs to go through and erase all the blocks. So I can see that taking more than a few seconds (but still less time than it would take to write zeros to the entire SSD).