SSD without a L3 improvement

[DarkwinX]

Thought I'd open up the discussion on an SSD I have which doesn't improve its read performance after an L3 or even L5 scan.

Attached are some before and after shots. The after is actually after an L3, L5 and an L3 with a forced xfer of 32MB Incase the cache was getting in the way.

At this point could it be just degraded cells or bad firmware?

 

[drwtsn32]

Have you tried doing a "secure erase"? On an SSD this only takes a few seconds, and supposedly it can reset performance back to default in some situations.

 

[DarkwinX]

Hmm I wonder if it will truly give an increase. AFAIK what will happen is that the underlying MLC will get purged of data but the mapping table will also get reset.

So until new data is written it will probably seem to operate at max speed due to being unmapped, and then will revert back.

Will give it a shot anyway and see.

 

[Steve]

Hmm I wonder if it will truly give an increase. AFAIK what will happen is that the underlying MLC will get purged of data but the mapping table will also get reset.

We were discussing this recently. It's certainly for an "insecure erase" to simply wipe the mapping table — what's known as the FTL, the Flash Translation Layer. This would be no different than TRIMming the entire drive surface. And since the underlying data would not have been immediately wiped it's not secure. But we're told that a "secure erase" will not only do that, but that it will also proactively wipe the entire drive's underlying data.

So, it would be quite interesting to learn whether a secure erase is able to do for an SSD what a L3 or L5 cannot.

Remember, though that the drive will APPEAR to be screaming immediately following a secure erase because real reading will not be occurring. So you'll need to run an L3 pass afterward to remap the logical addresses to physical media.

 

[DarkwinX]

So I completed a secure erase on the drive, ran the benchmark and as expected the maximum read results were seen due to the erased FTL.

I then completed a level 3 and performed the benchmark again and the front of drive rate appears to be closer to maximum speed again.
If we assume that Spinrite was working correctly in the original test then that means that the benchmark results were indicative of some other issue with the NVM.

Would erasing the FTL (and the underlying data) result in the suspected bad NVM to be randomly spread across the new FTL mapping? Therefore what was the "front of the drive" could be spread across the entire drive now and the read performance impact averaged across the drive as well?

 

[DarkwinX]

OTOH read's crawl after a refresh THEN there may be reason for concern.

That's what my first post is saying. Using Spinrite to refresh (L3) gave no improvement to the front of the drive, it hovered around 300 Mbps.

It took a secure erase and then a refresh (L3) to show a full improvement (from 300ish Mbps to 500ish Mbps.

Since we've seen time and again that an L3 always brings an SSD much closer to the link speed, I'm inclined to think it was an issue with the underlying NAND.

 

[drwtsn32]

Would erasing the FTL (and the underlying data) result in the suspected bad NVM to be randomly spread across the new FTL mapping? Therefore what was the "front of the drive" could be spread across the entire drive now and the read performance impact averaged across the drive as well?

I don't have an answer, but I have seen similar results in the past with some SSDs.

Was the SSD used on an OS and/or controller that didn't support TRIM?

 

[Steve]

So I completed a secure erase on the drive, ran the benchmark and as expected the maximum read results were seen due to the erased FTL.

I then completed a level 3 and performed the benchmark again and the front of drive rate appears to be closer to maximum speed again.
If we assume that Spinrite was working correctly in the original test then that means that the benchmark results were indicative of some other issue with the NVM.

SUPER Interesting testing, @DarkwinX. We know from many others' tests that SpinRite's passes can improve performance. What you've just demonstrated is that, as it is, it doesn't necessarily "must" improve performance. But SpinRite 7 is going to be all about doing that... so we have some very interesting explorations ahead!