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Based on a suggestion by eblock, I have run smartctl several times for the last few days to check for issues. Below, as an example, is the output of sudo smartctl -a /dev/nvme0n1p2:

smartctl 7.0 2019-05-21 r4917 [x86_64-linux-5.5.7-1-default] (SUSE RPM)
Copyright (C) 2002-18, Bruce Allen, Christian Franke, www.smartmontools.org

=== START OF INFORMATION SECTION ===
Model Number:                       Samsung SSD 970 EVO Plus 500GB
Serial Number:                      S4EVNZFN503427W
Firmware Version:                   2B2QEXM7
PCI Vendor/Subsystem ID:            0x144d
IEEE OUI Identifier:                0x002538
Total NVM Capacity:                 500,107,862,016 [500 GB]
Unallocated NVM Capacity:           0
Controller ID:                      4
Number of Namespaces:               1
Namespace 1 Size/Capacity:          500,107,862,016 [500 GB]
Namespace 1 Utilization:            94,943,219,712 [94.9 GB]
Namespace 1 Formatted LBA Size:     512
Namespace 1 IEEE EUI-64:            002538 5501ad2a18
Local Time is:                      Wed Dec  2 11:19:04 2020 CET
Firmware Updates (0x16):            3 Slots, no Reset required
Optional Admin Commands (0x0017):   Security Format Frmw_DL Self_Test
Optional NVM Commands (0x005f):     Comp Wr_Unc DS_Mngmt Wr_Zero Sav/Sel_Feat Timestmp
Maximum Data Transfer Size:         512 Pages
Warning  Comp. Temp. Threshold:     85 Celsius
Critical Comp. Temp. Threshold:     85 Celsius

Supported Power States
St Op     Max   Active     Idle   RL RT WL WT  Ent_Lat  Ex_Lat
 0 +     7.80W       -        -    0  0  0  0        0       0
 1 +     6.00W       -        -    1  1  1  1        0       0
 2 +     3.40W       -        -    2  2  2  2        0       0
 3 -   0.0700W       -        -    3  3  3  3      210    1200
 4 -   0.0100W       -        -    4  4  4  4     2000    8000

Supported LBA Sizes (NSID 0x1)
Id Fmt  Data  Metadt  Rel_Perf
 0 +     512       0         0

=== START OF SMART DATA SECTION ===
SMART overall-health self-assessment test result: PASSED

SMART/Health Information (NVMe Log 0x02)
Critical Warning:                   0x00
Temperature:                        38 Celsius
Available Spare:                    100%
Available Spare Threshold:          10%
Percentage Used:                    0%
Data Units Read:                    382,321 [195 GB]
Data Units Written:                 695,579 [356 GB]
Host Read Commands:                 4,525,857
Host Write Commands:                9,680,786
Controller Busy Time:               30
Power Cycles:                       205
Power On Hours:                     75
Unsafe Shutdowns:                   73
Media and Data Integrity Errors:    0
Error Information Log Entries:      209
Warning  Comp. Temperature Time:    0
Critical Comp. Temperature Time:    0
Temperature Sensor 1:               38 Celsius
Temperature Sensor 2:               41 Celsius

Error Information (NVMe Log 0x01, max 64 entries)
No Errors Logged

The lines "SMART overall-health self-assessment test result: PASSED" and "No Errors Logged" look reassuring, but the following line doesn't:

Unsafe Shutdowns:                   73

According to Using NVMe Command Line Tools to Check NVMe Flash Health by Peter Zaitsev (February 2017), Unsafe Shutdowns refers to

The number of times a power loss happened without a shutdown notification being sent. Depending on the NVMe device you’re using, an unsafe shutdown might corrupt user data.

There have been a few unexpected shutdowns on my Tuxedo notebook (see Is there a way to find the cause of unexpected power offs by inspecting logfiles?) but not 73 times.

According to this forum post on Tom's Harware (April 2019), disabling fast boot might help. Is this correct or is something else needed?

Tsundoku
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1 Answers1

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For some reasons I don't believe this SMART parameter is correct. For instance for my own SSD, I see:

174 Unexpect_Power_Loss_Ct  0x0032   100   100   000    Old_age   Always       -       75

which is patently wrong because I've pressed the reset button or had a power loss less than 20 times over the life span of this SSD.

The reason why you should be relatively safe is because before shutting down, systemd tells the kernel to flush buffers, so all the dirty caches are actually dumped to the device.

Just never forget about regular proper backups - that's the most important thing.

Artem S. Tashkinov
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    Notice that there could be buffers inside the SSD as well, and while kernel flushed everything into the device, the device itself may not had dumped its buffers down to NV storage. This is exactly the event of "unsafe shutdown". Top SSDs incorporate supercapacitors to cope with this, I believe. Also, in general you shouldn't relate computer power downs with device power downs; the kernel may command any device to power down itself while the system stays powered and running. For example, HDDs often park heads, remember that fuss with WD Green. This shouldn't be "unsafe" shutdown though. – Nikita Kipriyanov Jul 29 '22 at 03:45