Comment by joe_mamba
15 hours ago
Man, I do wonder what the realistic lifespan of that single NAND chip will be after it gets hammered by constant swapping of running tasks way beyond the capabilities of a 8GB RAM machine.
I have a PC with a 10+ year old 256GB SATA Samsung SSD that's still in top shape, but that's different because that drive has those 256GB split over several NAND chips inside, so wear is spread out and shuffled around by the controller to extend lifespan. But when your entire wearable storage is a single soldered chip, I'm not very optimistic about long term reliability.
While high-density NAND is definitely worrying from a data retention standpoint, your reasons don't make sense. There has been a decrease in reliability with higher densities, and unless Apple is using SLC (strong doubt) you would expect around the same as any other manufacturer.
The sibling comments mentioning endurance don't tell the complete story either; continuously writing a drive until it shows errors means the cells have become leaky enough that they can't even hold data between each write and verify pass (hours or minutes apart), and while people point to such studies as "proof" that NAND endurance isn't something to worry about, they forget that endurance and retention are inversely related, as with temperature, and this is a statistical effect, so the true specification is more like "X years/months at temperature T after Y cycles with a BER of Z"; each one of those variables can be adjusted to make the others look as good or bad as you want.
There was quite a bit of discussion about that when the M1 first came out, but none of it really seemed to have happened six years later. The target audience isn't in danger of wearing it out and the ones that will push the limits will grow tired of it and sell it in a year or two or move on to the Neo 2, which might have 12gb of ram due to the expected chip.
I still think it's a great machine, but I think all these worries about NAND dying really haven't come to fruition, and probably won't. I have about a hundred plus of various SSD Macs in service and not one has failed in any circumstance aside from a couple of battery issues (never charged and sat in the box for 2 years, and never off the charger).
>There was quite a bit of discussion about that when the M1 first came out, but none of it really seemed to have happened six years later.
1. How do you know nothing happened? Define nothing in this case. Do Mac users check and report their SSD wear anywhere?
2. Didn't the OG 256gb M1 have 2 128MB NAND chips instead of one 256 meaning better wear resistance?
If swapping was causing SSDs to fail on M1 Macs, we would never see the end of the hysterical articles about "NANDgate". Since we haven't seen any in all these years, it's seems pretty certain it's not happening.
7 replies →
> Do Mac users check and report their SSD wear anywhere?
As a data point: I got a 14" MacBook Pro with a 512 GB SSD the first day it was available in 2021, and I've used it daily since then.
According to the SMART data ("smartctl -x /dev/disk0"), the SSD "percentage used" is 7%, with ~200 TBW. At this rate, the laptop will probably outlive me.
>but that's different because that drive has those 256GB split over several NAND chips inside, so wear is spread out and shuffled around by the controller to extend lifespan. But when your entire wearable storage is a single soldered chip, I'm not very optimistic about long term reliability.
I thought wear leveling worked at the page/block level, not the chip level? On an SSD, if there was a failure of an entire chip, you're still screwed.
You're correct, GP's understanding of how wear leveling works is off by several layers. Counting the number of BGA packages tells you nothing. There are multiple NAND dies per package, multiple planes per die, many blocks per plane, and the size of each erase block is the largest-scale feature that is relevant to wear leveling.
from what i seen in "low end" ssds like the "120gb sata sandisk ones" under windows in heavy near constant pagging loads is that they exceed by quite a lot their manufacturer lifetime TBW before actually actually started producing actual filesystem errors.
I can see this could be a weaker spot in the durability of this device, but certainly it still could take a few years of abuse before anything breaks.
an outdated study (2015) but inline with the "low end ssds" i mentioned.
https://techreport.com/review/the-ssd-endurance-experiment-t...
The M2 MacBook Air base model has 8GB RAM and a single 256GB NAND chip. Nearly 4 years later, it doesn't seem to have caused any problems.
Most flash has average wear out after 300k cycles. Let's say 64GB is used for swap. That's 19200 TB or 19.2 PETABYTES of Swap usage. Let's say you swap 12GB a day, you will burn out that 64GB of Flash Storage in 4.38 years and my guess is that amount of swap usage is extremely high that user would probably replace laptop sooner out of performance frustration.
>Most flash has average wear out after 300k cycles
No it doesn't. Most 1TB drives are rated for around 600 TBW, so enough to overwrite the drive 600 times, nowhere near 300k cycles. If you search for specs of NAND chips used in SSDs, you'll find they're rated for cycles on the order of hundreds to thousands, still nowhere near "300k".
https://www.techpowerup.com/ssd-specs/crucial-mx500-4-tb.d95...
Original mid-90s Toshiba "solid state floppy disk" SLC flash: 1M cycles
2000s SLC flash: 100K cycles
Modern SLC/pSLC flash: 30-60K cycles
2010s MLC flash: 5-10K cycles
Modern QLC flash: 300-500 cycles
...and I won't even get into the details of their retention characteristics, suffice to say they subtly redefined them over the years to make the newer numbers better than they really are.
12GB a day isn't very much. If your working set is larger than the 8GB RAM, you're swapping multiple times per second. It doesn't take very many megabytes per swap to reach 12GB if you're doing that multiple times per second.
that doesn't maths