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toke lahti

macrumors 68040
Original poster
Apr 23, 2007
3,270
502
Helsinki, Finland
I recently researched why my old macmini's Fusion drive broke.
From SSD's (used it in 2017-2019) SMART:
Code:
9 Power_On_Hours          0x0032   100   100   ---    Old_age   Always       -       9872
233 Total_NAND_Writes_GiB   0x0032   100   100   ---    Old_age   Always       -       111692
234 Perc_Write/Erase_Ct_BC  0x0032   100   100   ---    Old_age   Always       -       177455

Meaning 111TB or 177TB of writing in that ssd.
It's SanDisk SD8SB8U128G1122 with TBW of 72.
No wonder that it broke. Used 10.12 Sierra with that installation.

Then I checked my old mbp.
Current Fusion drive in use from 2014.
Code:
9 Power_On_Hours_and_Msec 0x0032   079   079   000    Old_age   Always       -       18946h+18m+30.970s
233 SandForce_Internal      0x0032   000   000   000    Old_age   Always       -       232691
234 SandForce_Internal      0x0032   000   000   000    Old_age   Always       -       191868
241 Lifetime_Writes_GiB     0x0032   000   000   000    Old_age   Always       -       191868

That probably means 233TB of NAND writes!
It's KINGSTON SV300S37A120G with TBW of 64, but it still shows 38% life left!

Seems to be, that the "Swapping scandal" 2 years ago was just the tip of old iceberg.
Haven't done anything special with those macs, mbp was in constant use in 2014-2016, but after that very light use.

I'd be very interested to see, especially old Fusion drives ssd wear with older macOD versions.
Also would be interesting to see if there's any difference with later macOS versions.
 

Fishrrman

macrumors Penryn
Feb 20, 2009
28,323
12,445
This is why I DISABLE VM disk swapping on my Macs.

One has to have a sufficient amount of RAM to do this (for my 2012 Mini, 10gb was enough; for my 2018 Mini and 2021 MBP 14", 16gb is enough).

And... one has to be aware of how many apps are open and close unused apps.
Also, I do not use "tabbed browsing"... AT ALL.

But... no VM "works for me".
VERY WELL, as a matter fact.
NO memory-related crashes.
 
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toke lahti

macrumors 68040
Original poster
Apr 23, 2007
3,270
502
Helsinki, Finland
This is why I DISABLE VM disk swapping on my Macs.

One has to have a sufficient amount of RAM to do this (for my 2012 Mini, 10gb was enough; for my 2018 Mini and 2021 MBP 14", 16gb is enough).

And... one has to be aware of how many apps are open and close unused apps.
Also, I do not use "tabbed browsing"... AT ALL.

But... no VM "works for me".
VERY WELL, as a matter fact.
NO memory-related crashes.
So, can you list your ssd’s NAND writes from SMART?
 

Fishrrman

macrumors Penryn
Feb 20, 2009
28,323
12,445
"So, can you list your ssd’s NAND writes from SMART?"

OK, not sure if I did this correctly.
I used Smart Utility.
It produced this readout:
screenshot.jpg

Am I to assume that the total number of reads/writes to the drive (since new) are reported as:
Data Units Read - 17.9tb
Data Units Written - 10.4tb
???

This is for a 2018 Mini purchased in January 2019.
So it's now just over four years old.
Averages out to 2.6tb per year.

If that's the case, compare my numbers above to some relatively new m-series Macs, with many many times the amount of terabytes read/written...
 

toke lahti

macrumors 68040
Original poster
Apr 23, 2007
3,270
502
Helsinki, Finland
"So, can you list your ssd’s NAND writes from SMART?"

OK, not sure if I did this correctly.
I used Smart Utility.
It produced this readout:
View attachment 2166627
Am I to assume that the total number of reads/writes to the drive (since new) are reported as:
Data Units Read - 17.9tb
Data Units Written - 10.4tb
???

This is for a 2018 Mini purchased in January 2019.
So it's now just over four years old.
Averages out to 2.6tb per year.

If that's the case, compare my numbers above to some relatively new m-series Macs, with many many times the amount of terabytes read/written...
Maybe that's not the boot drive?
Try this: https://www.corecode.io/smartreporter/
Or you just use that mini 1 week per year?
 

Fishrrman

macrumors Penryn
Feb 20, 2009
28,323
12,445
"Maybe that's not the boot drive?"

It's the ONLY drive connected and running.
I use the Mini 7 days a week.
Usually turned on about 8.45am and shut down around 11.45pm.
Sometimes I turn it off for a few hours mid-day if I'm going out.

It's my "main Mac".
The read/write numbers on the SSD speak for themselves, when measured vis-a-vis against SSDs in Macs that have VM disk swapping running continually.
 

toke lahti

macrumors 68040
Original poster
Apr 23, 2007
3,270
502
Helsinki, Finland
"Maybe that's not the boot drive?"

It's the ONLY drive connected and running.
I use the Mini 7 days a week.
Usually turned on about 8.45am and shut down around 11.45pm.
Sometimes I turn it off for a few hours mid-day if I'm going out.

It's my "main Mac".
The read/write numbers on the SSD speak for themselves, when measured vis-a-vis against SSDs in Macs that have VM disk swapping running continually.
And the "Power on Hours" does not speak for itself.
Clearly there is something wrong in that smart data, we just do not know how much?

And the interesting part is attribytw #233.
Which, if you know TBW, will tell you the most about life expectancy.
 

anika200

macrumors 6502
Feb 15, 2018
448
607
USA
=== START OF SMART DATA SECTION ===
SMART overall-health self-assessment test result: PASSED

SMART/Health Information (NVMe Log 0x02)
Critical Warning: 0x00
Temperature: 32 Celsius
Available Spare: 100%
Available Spare Threshold: 10%
Percentage Used: 8%
Data Units Read: 11,803,533 [6.04 TB]
Data Units Written: 32,325,957 [16.5 TB]
Host Read Commands: 382,980,436
Host Write Commands: 1,829,735,248
Controller Busy Time: 8,705
Power Cycles: 523
Power On Hours: 13,709
Unsafe Shutdowns: 51
Media and Data Integrity Errors: 0
Error Information Log Entries: 0
Warning Comp. Temperature Time: 0
Critical Comp. Temperature Time: 0
Thermal Temp. 1 Transition Count: 4
Thermal Temp. 1 Total Time: 349

Error Information (NVMe Log 0x01, 16 of 256 entries)
No Errors Logged
Mine has basically the opposite Read and Written data as @Fishrrman , interesting.
 
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toke lahti

macrumors 68040
Original poster
Apr 23, 2007
3,270
502
Helsinki, Finland
Mine has basically the opposite Read and Written data as @Fishrrman , interesting.
13709 hours, so that's only 1,2 GB/h.

Btw, anybody has any idea how much energy is needed to write 1GB to ssd?
Doesn't this eat the battery life?

Wondering how much using windows wears the ssd...?

Since Apple doesn't want to tell real NAND writes, but maybe says that 8% of life expectancy is used, doesn't that mean the ssd has TBW of 206?

Is that a 512GB ssd?
 
Last edited:

anika200

macrumors 6502
Feb 15, 2018
448
607
USA
Ahh man bummer, my imac drive I installed does not support S.M.A.R.T. Whats up with that?
Update -- it seems supported ( I had to select the container in Disk Utility) but how to get an actual report?

Code:
Volume type : APFS Container
BSD device node : disk1
Connection : PCI-Express
Device tree path : IODeviceTree:/PCI0@0/RP17@1B/SSD0@0/IONVMeController
Writable : No
Is case-sensitive : No
Volume capacity : 1,920,039,436,288
Available space (Purgeable + Free) : 1,557,972,324,352
Purgeable space : 0
Free space : 1,557,972,324,352
Used space : 362,067,111,936
Owners enabled : No
Is encrypted : No
Can be verified : Yes
Can be repaired : Yes
Bootable : No
Journaled : No
Disk number : 1
Media name : AppleAPFSMedia
Media type : Generic
Ejectable : No
Solid state : Yes
S.M.A.R.T. status : Verified
 
Last edited:

toke lahti

macrumors 68040
Original poster
Apr 23, 2007
3,270
502
Helsinki, Finland
Ahh man bummer, my imac drive I installed does not support S.M.A.R.T. Whats up with that?
Update -- it seems supported ( I had to select the container in Disk Utility) but how to get an actual report?

Code:
Volume type : APFS Container
BSD device node : disk1
Connection : PCI-Express
Device tree path : IODeviceTree:/PCI0@0/RP17@1B/SSD0@0/IONVMeController
Writable : No
Is case-sensitive : No
Volume capacity : 1,920,039,436,288
Available space (Purgeable + Free) : 1,557,972,324,352
Purgeable space : 0
Free space : 1,557,972,324,352
Used space : 362,067,111,936
Owners enabled : No
Is encrypted : No
Can be verified : Yes
Can be repaired : Yes
Bootable : No
Journaled : No
Disk number : 1
Media name : AppleAPFSMedia
Media type : Generic
Ejectable : No
Solid state : Yes
S.M.A.R.T. status : Verified
I use SMARTReporter.
Most known is perhaps DriveDX.
Both need SATsmart for external drives.

Apple, of course, has no intensions to let its users to see mac's storage's SMART values.
 
Last edited:
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