CwF wrote: ↑2022-05-10 17:03
Now SMR I'd think gets irritated with trim!
I'm not sure what do You mean by SMR - Shingled Magnetic Recording?
CwF wrote: ↑2022-05-10 17:03
Actually as I've pointed out elsewhere, I think it is "unneeded". On device, while active, I never used it.
Of course, I know that Your SSDs are "very special", and I don't want to start "that discussion" again.
Short history of SSDs:
Technically, TRIM was not needed in the 1st generation of SSDs, that is, for SLC NAND flash chips.
Those devices were so reliable, that there was (almost) no need to implement any error correction algorithms in the NAND Flash controller.
All the newer generations of SSDs are designed to be cheap - the reliable SLC technology has been abandoned in favour of much cheaper but also much less reliable technologies: SLC->MLC->TLC->QLC->PLC.
From technical point of view, MLC and its successors are a complete sh.it: it's impossible to successfully read the memory content without using sophisticated error correction algorithms.
The newer the type of SSDs, the more read errors, and so the stronger error correction algorithms have to be used.
This obviously comes at a cost:
The error correction takes significant amount of time - it slows down the SSD operations long before the memory page becomes completely worn-out (where "completely worn-out" means that the error correction algorithm is no longer able to correct the read errors)
The are 2 main purposes of TRIM command:
1. Writes to an unused (trimmed) SSD memory allows to avoid write-amplification (read-modify-write operations)
2. Because of the above (no read operation), the error correction algorithms are not used, so such write operations can be really fast.