M1 SSD high read and write usage per smartctl

Robert Follis wrote:

6.6TB a month = 792TB annually which is the total life of some SSDs

He's reporting 6 point 6 TB per month, not 66TB.

Anyway, I think what we're forgetting here (myself included) is that the Percentage Used number is based on what the Apple SSD itself is reporting, so if it is reported as 1000TBW, that's pretty much what Apple is guaranteeing.

So, in the case of Robert, I'd say your best bet is to just use the Mac and forget about the SSD usage, and aim for it to reach 100% before it's out of warranty., as long as it isn't impacting your use of the Mac. If Apple doesn't honor its hardware warranty and/or implicit 1000TBW guarantee then you and anyone else in this situation will have a good legal case. Just make sure you have a backup.

As for sfromgi, such an option is little less clear, but I'd suggest forgetting about "lite use" and just go ahead and use it as normal, and keep regular backups. It's unlikely that sfromgi's SSD will fail due to writes. Like I've pointed out, mine is 227TBW in close to four years and has zero errors, but if his usage with other than light use is much higher, he'll also be in line for a warranty replacement.

The part of smartctl relevant to SSD life is the Percentage Used. You have about 1% used, but since it's rounded it could be anywhere from 1-2%, so you have between 98-99% of your SSD life left. Your Mac was 3 months old when you posted this, so you can expect 150-300 months life out of it.

Percentage Used:                    1%
Data Units Read:                    29,157,637 [14.9 TB]
Data Units Written:                 24,058,076 [12.3 TB]

My own 3.75 year old 15" MBP is showing Percentage Used: 21%, so I can expect another 14 years from it. It shows that my SSD TBW is estimated at 1000TB. If yours is also 1000TBW, you would expect about 250months life based on 12.3TB in three months

Percentage Used:                    21%
Data Units Read:                    513,695,304 [263 TB]
Data Units Written:                 444,977,968 [227 TB]

However, Robert Follis is showing a real issue

My M1 MBP 8/256 has used 21% of SSD life in 5 months writing 258TB !! to disk.

He has used as much of his SSD lifetime in five months as I have in nearly 4 years.

All I can suggest is he carefully check what's doing the writes. Activity Monitor -> Disk -> order by Bytes Read will show what's doing the most writing to disk.

Of course, the expected life is only an estimation. We would need to be able to track actual failed SSDs against the estimated TBWs. I'm sure manufacturers are doing that but I don't know how we, as consumers, would get real numbers.

For one, reads don't matter with SSDs, only writes.

I have been investigating this "issue" as well. I checked out 3 different

SMART tools all of which gave different usage data. Also, when comparing

to what Activity Monitor is saying for the number of bytes, it doesn't jive

with these tools reports. As a matter of fact, one day, Activity Monitor

said there were 40 GB of writes and smartctl actually reported that

TBW went down by 10 GB!

Another example today, I did a photo processing session and Activity Monitor

showed nearly 70 GB of writes, but only 500 MB swap was used so it is not

a RAM swapping issue and based on Activity Monitor, the apps that were used never

did more than a couple GB of writes. After checking the Smart tools I had,

one said about 30 GB was written another said only about 10 GB was written

and a third said 40 GB was written.

Also, some of the SMART tools themselves do not have numbers

that make sense to give the totals they are getting, i.e. sectors

written times sector size do not add up to total bytes written.

Personally, I believe the following:

1) The SSDs in the M1 machines are not totally documented in terms of

SMART status available and formats of the data and how they should be

read and interpreted..

2) While Activity Monitor has been around a long time, I believe there

are reporting issues with it as well.

3) Until there are reliable tools to measure the usage, no one really

knows how many writes (or reads) there really are being done.

Just looking at your data, units/sectors written being reported is 24 MB.

The M1 SSD sector size is 4096 (if that is even being reported correctly.

The math says the total number of writes should be ~120 GB, which is

awfully close to a difference factor of 1000. So, is the units read correct?

Is the total calculation incorrect? Is the sector size/unit size even correct?

Is Big Sur going berserk with writes? Is anything correct?

woodmeister50 wrote:

I have used smartctl to get info on SSDs, and different manufacturers

supply a wide variety of different information support and some

and not all adhere to the SMART standard and often take

"artistic license" in encoding their information. There was an iteresting

article on the DriveDx blog that pretty much said maintaining their software

is chasing a moving target, if it is even visible.

I agree. The drive manufacturers of hard drives and SSD have shown over the years they sometimes have broken SMART implementations. For example for years I have seen the "Power On Hours" for hard drives to show one value while the time stamp for a log entry is completely different. This is very basic functionality and reporting yet the drive manufacturers get this wrong all the time. Sometimes the timestamps for the logs are all the same or even zero. There are other examples where the SMART attributes are implemented outside of spec. Most of these drive manufacturers don't even document these health attributes. It is a shame that such a useful monitoring feature has so little attention to detail and that the health monitoring of NVMe SSDs has become so simplified. I'm assuming they are hiding the details because with each advance on SSD NAND tech the speed and life expectancy of the NAND gets worse & worse so they want to hide this from users.

I personally believe the smartctl utility is most likely properly retrieving the information from the SSD. I personally believe the SSD is most likely reporting the information incorrectly. However, like all the drive manufactures Apple will never tell us if this is the case and it will most likely remain unknown until we see the SSDs fail or we see these TBW exceed the common values for SSDs.

Most NVMe SSDs only report the bare basics unlike the older SATA SSDs where we had the actual known values & thresholds to translate them into easily understood indicators. Only the "RAW" values were to be questioned since the utilities were calculating the "RAW" value which typically included the exact number of errors or the exact amount of data transferred.

Until someone verifies that the values for "Data Units Written" actually matches the amount of data truly written to the SSD through a test we have no idea if this value is truly accurate or whether we are off by a certain unit of measure. We'll also have our answer once one of these SSDs wears out if these reported values are actually correct. Most standard SSDs typically have a max TBW (TerraBytes Written) of 300TB (of course this varies especially by the size of the SSD).

I found an interesting piece on the DriveDx site. It seems the

"Raw" value that all these apps use to determine total bytes written

can be cloaked in mystery especially with a brand new drive. It

stated:

"Each health indicator (S.M.A.R.T. attribute) has a raw value aka raw data. Raw measured values (provided by a sensor or a counter) are stored in this field. Sometimes different parts (high word, low word, etc) of raw value contain different kind of information.

The drive manufacturer defines the meaning of this value (but often corresponds to counts or a physical unit). The exact meaning of raw value often considered as trade secret. These values may significantly vary between different manufacturers and drive models and should NOT be compared with other devices or other vendors."

So, it would appear that unless Apple has released the precise details of this

value, perhaps all the readings are bogus. Could it mean the values are

significantly lower or even higher? It seems no one really knows for sure at

this point. Actually, reading through that entire page, without precise manufacturer

definitions nearly every value that may be read in SMART status could be ?????.

The explanation:

https://binaryfruit.com/drivedx/help#ui-health-indicators-raw-value

Sfromgi, I don’t think you or the OP have anything to worry about, but Robert.follis does.

Your use isn’t too far off my 45 month old MBP and I don’t have any concerns about mine. I’m pretty sure I can get at least the same amount of time out of it but I’ll probably replace it long before then.

it’s been 15+ years since I used Windows so I don’t know what it is you’re using to measure writes on your Windows laptop, but even if its TBW was at the lower end, 150TBW, that would be an expected lifetime of 100 years. So assuming 3TB in two years is correct, it’s overkill.

I’m willing to bet that the writes are almost exclusively due to swapping, so you need to look at the Memory tab in Activity Monitor. But go to the menu, View -> Columns, and turn on the Real Memory columns. macOS processes share a lot of memory, so looking at the Real Memory use tells you how much each process is using exclusively.

As for me, I’m a software developer who does a lot of work in AWS. I work with two different AWS accounts so I usually run two different browsers so I don’t have to switch accounts. I used Firefox and Chrome. Beginning last year I started to get a lot of memory pressure issues - causing a lot of swaps, and I could see that it was the Chrome tabs grabbing a lot of memory, so I switched to using Safari. I haven’t had any memory pressure issues since.

Open up activity monitor and go to the disk tab. Look for the kernel_task process and that will give you an idea of what is being written to the SSD. Then click apple button in menu bar, "about this mac" and then click "system report" click on "Software" and in the main panel check the "Time Since Boot". This will give you an idea of how intensively the disk is being written to.

In my case it is nearly six days since boot and the kernel_task process has written just over 5TB (Two of those days were the weekend when I probably used my macbook pro a little less).

Now, I have had my MacBook 75 days, so if I now check the output of sudo smartctl --all /dev/disk0 :

Percentage Used: 2%
Data Units Written: 160,257,271 [82.0 TB]

So 82TB over 75 days is ~1.1 TB per day and seems to tally with what the activity monitor is reporting.

So I think the issue is real.

One thing to note, many NVMe SSDs can have significantly large

amounts of built in DRAM. With proper management, many of the temp

writes (caches, swap, etc.) may never even reach the actual NAND cells

of the SSD.

The DRAM in the SSD is used to speed the writes up as a direct write

to the NAND cells is comparatively slow.

As one last additional note, it seems that heavy use of Intel apps

can be a culprit of excessive writes. With some investigating, I

found that one photo processing app I used grew to a point on

my M1 MacBook Air so much that it was using 10 GB of swap

and as such, a lot of writes were constantly taking place and was

basically continually swapping. I have the same app on an Intel iMac

and I duplicated the same session exactly and the app never used

more than 2GB. It seems there may be an issue with Rosetta 2

not properly managing memory allocation (a leak?) to a point

where it does not return memory requested and then released

by an application.

Also, with the M1 being so fast and efficient and the blazing speed

of the SSD, heavy memory swapping is not even noticed like

it would in the old days with massive slow down and spinning

beachballs.

There is also no telling how smartctl is getting

its information for "lifetime". Since it is not a published

number for Apple SSDs, they are likely using some low end

guess.

I have used smartctl to get info on SSDs, and different manufacturers

supply a wide variety of different information support and some

and not all adhere to the SMART standard and often take

"artistic license" in encoding their information. There was an iteresting

article on the DriveDx blog that pretty much said maintaining their software

is chasing a moving target, if it is even visible.

All that aside, while the smartctl absolutes could be more or less meaningless,

the relative numbers from one user to another (assuming they are on exactly

the same platform) are not.

Yes but that’s pretty much certain to be swapping. If you can track down the actual app that’s having its memory swapped you’d be closer to a solution.

There is one last thing that is at this point a total unknown.

That is who makes the SSD chips for Apple and what are

their lifetime TBW.

From some quick research, for say a 512 GB NVMe drive, I found

TBW lifetimes range from 300 TBW to as high as 1200 TBW.

There are also a wide range of things that contribute to that

such as over-provisioning (how much "extra" SSD space is

in the Apple SSDs), wear leveling (the SSD deals with this and

APFS also helps it), how robust is the error detection and correction,

etc.

So, without the actual TBW lifetime, one is not sure to just

be "concerned" or to be "panicked".

I have written 3TB in 7 days of use. I have the 16GB Mem version. If the TBW is 300, the Mac will be dead in 2 years, as the SSD is not replaceable. Less if I use it as I want to use it (as a SW dev, I want to be constantly rebuilding my apps, starting / stopping services, running local databases etc.)

i have started using My PC more, to save the Mac self destructing. i try to keep fewer apps open at the same time to reduce paging, but this makes the Mac more painful to use. I try to shut down the mac when not in use, to avoid it writing during sleep. I have uninstalled whatsapp, and now only use this on the phone.

The posts saying that the TB written reading might not be accurate sounds like wishful thinking, but lets hope. Using the PC has reminded me how bad the MacOS finder is compared with file explorer, but how good Outlook mac is compared with windows version (no unified inbox etc).

I fully agree with your explanation. The way the SMART raw values should be decoded can be different by device/manufacturer. For instance, if you look at Crucial web site: https://www.crucial.com/support/articles-faq-ssd/ssds-and-smart-data they are explaining how the SMART raw 202 attribute should be decoded and, in this case, it corresponds with the definition. Coming back to Macbook NVME drives, if I use smartctl on my Macbook of 2017 (that I'm using 8 hours on each working day), it reports only 1% used and 17 TB written and this does not obviously correspond to the real use I did.

Unfortunately issues with SMART reporting have been around since the beginning since drive manufacturer's don't always provide the necessary information to properly interpret the real values. It is crazy that such a useful feature is not properly documented by the drive manufacturer. Does DriveDx or smartcl provide the old style table layout of the attributes to show the "Value", Worst", and "Threshold" reporting? If so, then that is the best way to monitor the health of the drive as the drive will automatically decrement the "Value" and "Worst" as the attribute ages. Computing the "RAW Value" depends upon knowing how that value is stored.

I've been monitoring our organization's Intel Macs more closely after we received a worn out SSD after having a 2017 MBPro Logic Board replaced by Apple (the SSD failed within 90 days of the repair and had used up all its blocks -- there is no way the user wrote that much data to the SSD in 90 days). Ever since I've checked each SSD that Apple has replaced and I've even compared them to other SSDs from laptops that have not been repaired. I've noticed that the SMART values being reported are eerily similar to each other and even to the values reported by the OP here. The interesting thing is the USB-C Macs all have SSDs identified as Apple (AP) whereas the older non-USB Macs had the SSDs identified by the real manufacturer such as Samsung (SM), Toshiba, or SanDisk, etc.