I use S.M.A.R.T. selftest to test all of my hard drives and SSDs. I run a short test daily and a long test monthly.
One of my SSD is showing odd behavior in that the lifetime hours seem to reset back to zero. Is this normal? Why would it do this? I have never seen this behavior before. Is it a cause for concern?
The command I use to initiate the tests (via a script launched by crontab) is:
smartctl --test=short $DISK
Here is a copy of the error log that shows the strange behavior:
smart self-test log structure revision number 1
num test_description status remaining lifetime(hours) lba_of_first_error
# 1 short offline completed without error 00% 110 -
# 2 short offline completed without error 00% 86 -
# 3 short offline completed without error 00% 62 -
# 4 short offline completed without error 00% 38 -
# 5 short offline completed without error 00% 14 -
# 6 short offline completed without error 00% 1166 -
# 7 short offline completed without error 00% 1142 -
# 8 short offline completed without error 00% 1117 -
# 9 short offline completed without error 00% 1093 -
#10 short offline completed without error 00% 1069 -
#11 short offline completed without error 00% 1045 -
#12 short offline completed without error 00% 1021 -
#13 short offline completed without error 00% 997 -
#14 short offline completed without error 00% 973 -
#15 short offline completed without error 00% 949 -
#16 short offline completed without error 00% 925 -
#17 short offline completed without error 00% 901 -
#18 extended offline completed without error 00% 897 -
#19 short offline completed without error 00% 877 -
#20 short offline completed without error 00% 853 -
#21 short offline completed without error 00% 829 -
The device is much older than 1166 hours.
Here is some specific info on the device:
smartctl -a $DISK
/dev/disk0
smartctl 7.1 2019-12-30 r5022 [Darwin 18.7.0 x86_64] (local build)
Copyright (C) 2002-19, Bruce Allen, Christian Franke, www.smartmontools.org
=== START OF INFORMATION SECTION ===
Model Family: Apple SD/SM/TS...E/F/G SSDs
Device Model: APPLE SSD SM1024F
Firmware Version: UXM8JA1Q
User Capacity: 1,000,555,581,440 bytes [1.00 TB]
Sector Sizes: 512 bytes logical, 4096 bytes physical
Rotation Rate: Solid State Device
Device is: In smartctl database [for details use: -P show]
ATA Version is: ATA8-ACS T13/1699-D revision 4c
SATA Version is: SATA 3.0, 6.0 Gb/s (current: 6.0 Gb/s)
Local Time is: Sat Nov 7 15:18:13 2020 EST
SMART support is: Available - device has SMART capability.
SMART support is: Enabled
=== START OF READ SMART DATA SECTION ===
SMART overall-health self-assessment test result: PASSED
General SMART Values:
Offline data collection status: (0x00) Offline data collection activity
was never started.
Auto Offline Data Collection: Disabled.
Self-test execution status: ( 0) The previous self-test routine completed
without error or no self-test has ever
been run.
Total time to complete Offline
data collection: ( 0) seconds.
Offline data collection
capabilities: (0x5f) SMART execute Offline immediate.
Auto Offline data collection on/off support.
Abort Offline collection upon new
command.
Offline surface scan supported.
Self-test supported.
No Conveyance Self-test supported.
Selective Self-test supported.
SMART capabilities: (0x0003) Saves SMART data before entering
power-saving mode.
Supports SMART auto save timer.
Error logging capability: (0x01) Error logging supported.
General Purpose Logging supported.
Short self-test routine
recommended polling time: ( 2) minutes.
Extended self-test routine
recommended polling time: ( 10) minutes.
SMART Attributes Data Structure revision number: 40
Vendor Specific SMART Attributes with Thresholds:
ID# ATTRIBUTE_NAME FLAG VALUE WORST THRESH TYPE UPDATED WHEN_FAILED RAW_VALUE
1 Raw_Read_Error_Rate 0x001a 200 200 000 Old_age Always - 0
5 Reallocated_Sector_Ct 0x0033 100 100 000 Pre-fail Always - 0
9 Power_On_Hours 0x0032 093 093 000 Old_age Always - 33168
12 Power_Cycle_Count 0x0032 099 099 000 Old_age Always - 876
169 Unknown_Apple_Attrib 0x0013 253 253 010 Pre-fail Always - 7105251654656
173 Wear_Leveling_Count 0x0032 190 190 100 Old_age Always - 30084956220
174 Host_Reads_MiB 0x0022 099 099 000 Old_age Always - 77353745
175 Host_Writes_MiB 0x0022 099 099 000 Old_age Always - 58090980
192 Power-Off_Retract_Count 0x0012 099 099 000 Old_age Always - 202
194 Temperature_Celsius 0x0022 053 053 000 Old_age Always - 47 (Min/Max 23/72)
197 Current_Pending_Sector 0x0022 100 100 000 Old_age Always - 0
199 UDMA_CRC_Error_Count 0x001a 200 200 000 Old_age Always - 0
240 Unknown_SSD_Attribute 0x0022 100 100 000 Old_age Always - 0
SMART Error Log Version: 1
No Errors Logged
SMART Self-test log structure revision number 1
Num Test_Description Status Remaining LifeTime(hours) LBA_of_first_error
# 1 Short offline Completed without error 00% 110 -
# 2 Short offline Completed without error 00% 86 -
# 3 Short offline Completed without error 00% 62 -
# 4 Short offline Completed without error 00% 38 -
# 5 Short offline Completed without error 00% 14 -
# 6 Short offline Completed without error 00% 1166 -
# 7 Short offline Completed without error 00% 1142 -
# 8 Short offline Completed without error 00% 1117 -
# 9 Short offline Completed without error 00% 1093 -
#10 Short offline Completed without error 00% 1069 -
#11 Short offline Completed without error 00% 1045 -
#12 Short offline Completed without error 00% 1021 -
#13 Short offline Completed without error 00% 997 -
#14 Short offline Completed without error 00% 973 -
#15 Short offline Completed without error 00% 949 -
#16 Short offline Completed without error 00% 925 -
#17 Short offline Completed without error 00% 901 -
#18 Extended offline Completed without error 00% 897 -
#19 Short offline Completed without error 00% 877 -
#20 Short offline Completed without error 00% 853 -
#21 Short offline Completed without error 00% 829 -
SMART Selective self-test log data structure revision number 1
SPAN MIN_LBA MAX_LBA CURRENT_TEST_STATUS
1 0 0 Not_testing
2 0 0 Not_testing
3 0 0 Not_testing
4 0 0 Not_testing
5 0 0 Not_testing
Selective self-test flags (0x0):
After scanning selected spans, do NOT read-scan remainder of disk.
If Selective self-test is pending on power-up, resume after 0 minute delay.
How you can see from SMART attribute 9, your SSD lifetime is correcly reported in the full report:
On the other hand, the
LifeTime(hours)value reported for self/short/long tests seems to wrap at ~49 days, similar to how SMART error reporting works. From smartctl man page:This is one of the field where the once consumer related SMART heritage shows, as it is (was?) uncommon for a desktop to have >49 days uptime.
Most disks with SMART would use 16 bits to store this value, giving 65,535 hours before reset.
Yours appears to wrap after 1152 hours which is not a convenient power of 2 and is quite odd.
Here's a disk that has just completed its second time around that clock, with 139,895 hours of power-on time, but the SMART self tests wrap at 65,535 hours.
Yes this disk has about 16 years of active power-on time.
I'd suspect your Apple SSD has some extra firmware fudges going on allowing it to report odd times. It would be interesting to check the SMART values on a non-apple disk, attached by USB perhaps? Or to check an apple firmware disk in a non-apple system.