Comment by alliao
4 years ago
I thought Crucial specifically designed some power loss protection as a differentiating selling point? Well at least that was the reason why I bought one back in M.2 days (gosh my PC is ancient...)
4 years ago
I thought Crucial specifically designed some power loss protection as a differentiating selling point? Well at least that was the reason why I bought one back in M.2 days (gosh my PC is ancient...)
I think the most they ever promised for some of their consumer drives was that a write interrupted by a power failure would not cause corruption of data that was already at rest. Such a failure can be possible when storing multiple bits per memory cell but programming the cells in multiple passes, especially if later passes are writing data from an entirely different host write command.
Back in M.2 days? I know I'm getting old, but what did miss?
M.2 SATA as opposed to NVMe perhaps?
it's the storage form factor of my current PC.. which is probably close to 10yrs old :P
https://en.wikipedia.org/wiki/M.2
It is still being used in very recent PCIe Gen 4 NVMe drives.
Though you likely have a different key only taking SATA drives.
It changed [1] from capacitors and "power loss protection" to something else described as "power loss immunity" with the MX500. I don't think I've ever seen it explained very well.
> With the release of the MX500, Crucial has included a new replacement for the traditional power loss protection feature, power loss immunity. Instead of relying on a bank of capacitors for power loss protection, Crucial was able to work the new 3D TLC NAND and the code to allow for more efficient NAND programming so that the capacitors are no longer needed.
That's just a regurgitated press release IMO.
A lot of consumer drives also stopped reporting DRAT/RZAT [2] around the Crucial MX500, Samsung 850 timeframe. They swap internals as others in this thread have pointed out and the write endurance has dropped since reviewers stopped reporting on it. I have a Crucial MX500 in my system right now with 11% life remaining and only 37TBW even though it's advertised as having 180TBW of endurance.
Edit: I actually found [3] an explanation of "power loss immunity".
> The impact is still the same: you don't get the full protection that is standard for enterprise SSDs, but data that has already been written to the flash will not be corrupted if the drive loses power while writing a second pass of more data to the same cells.
I always thought write operations on SSDs were more or less to write a new page or block or whatever the terminology is and to flag the old one(s) for garbage collection. I don't understand how it would be possible to lose the old data by doing that. Did they just invent a term that sounds like power loss protection, but doesn't actually do anything special?
1. https://www.thessdreview.com/our-reviews/crucial-mx500-ssd-r...
2. https://forums.anandtech.com/threads/looking-for-new-ssd-tha...
3. https://www.anandtech.com/show/12165/the-crucial-mx500-1tb-s...
See https://people.inf.ethz.ch/omutlu/pub/flash-memory-programmi... for some of the things that can go wrong as a consequence of programming a cell in multiple passes, even without a power loss event.