SMART Devices

Listing 11: Vendor-Specific Attributes

# /usr/local/sbin/smartctl -a /dev/sda
smartctl 7.2 2020-07-11 r5076 [x86_64-linux-5.4.0-42-generic] (CircleCI)
Copyright (C) 2002-20, Bruce Allen, Christian Franke,
Model Family:     Samsung based SSDs
Device Model:     Samsung SSD 840 Series
Serial Number:    S19HNSAD620520T
LU WWN Device Id: 5 002538 5a0050931
Firmware Version: DXT08B0Q
User Capacity:    120,034,123,776 bytes [120 GB]
Sector Size:      512 bytes logical/physical
Rotation Rate:    Solid State Device
TRIM Command:     Available, deterministic, zeroed
Device is:        In smartctl database [for details use: -P show]
ATA Version is:   ACS-2, ATA8-ACS T13/1699-D revision 4c
SATA Version is:  SATA 3.1, 6.0 Gb/s (current: 6.0 Gb/s)
Local Time is:    Sun Aug  2 10:57:50 2020 EDT
SMART support is: Available - device has SMART capability.
SMART support is: Enabled
SMART overall-health self-assessment test result: PASSED
General SMART Values:
Offline data collection status:  (0x80) Offline data collection activity
                                        was never started.
                                        Auto Offline Data Collection: Enabled.
Self-test execution status:      ( 249) Self-test routine in progress...
                                        90% of test remaining.
Total time to complete Offline 
data collection:                (49272) seconds.
Offline data collection
capabilities:                    (0x53) SMART execute Offline immediate.
                                        Auto Offline data collection on/off support.
                                        Suspend Offline collection upon new
                                        No 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:        (  30) minutes.
SCT capabilities:              (0x003d) SCT Status supported.
                                        SCT Error Recovery Control supported.
                                        SCT Feature Control supported.
                                        SCT Data Table supported.
SMART Attributes Data Structure revision number: 1
Vendor Specific SMART Attributes with Thresholds:
  5 Reallocated_Sector_Ct   0x0033   100   100   010    Pre-fail  Always       -       0
  9 Power_On_Hours          0x0032   097   097   000    Old_age   Always       -       12441
 12 Power_Cycle_Count       0x0032   098   098   000    Old_age   Always       -       1482
177 Wear_Leveling_Count     0x0013   098   098   000    Pre-fail  Always       -       15
179 Used_Rsvd_Blk_Cnt_Tot   0x0013   100   100   010    Pre-fail  Always       -       0
181 Program_Fail_Cnt_Total  0x0032   100   100   010    Old_age   Always       -       0
182 Erase_Fail_Count_Total  0x0032   100   100   010    Old_age   Always       -       0
183 Runtime_Bad_Block       0x0013   100   100   010    Pre-fail  Always       -       0
187 Uncorrectable_Error_Cnt 0x0032   100   100   000    Old_age   Always       -       0
190 Airflow_Temperature_Cel 0x0032   070   065   000    Old_age   Always       -       30
195 ECC_Error_Rate          0x001a   200   200   000    Old_age   Always       -       0
199 CRC_Error_Count         0x003e   100   100   000    Old_age   Always       -       0
235 POR_Recovery_Count      0x0012   099   001   000    Old_age   Always       -       69
241 Total_LBAs_Written      0x0032   099   099   000    Old_age   Always       -       2909310200
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%     12441         -
# 2  Short offline       Completed without error       00%     12441         -
SMART Selective self-test log data structure revision number 1
    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
  255  28175872  28241407  Read_scanning was never started
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.

The first part of the output – the capabilities section – you’ve already seen with the -c option, but the second part is new. The table starting with ID# ATTRIBUTE_NAME FLAG contains the vendor-specific SMART attributes. The column to pay attention to is RAW_VALUE. For SSDs, a good first attribute to examine is in the first row, Reallocated_Sector_Ct, which is the count of reallocated sectors for the drive.

The drive has a pool of sectors held in reserve that can be used to swap out when it encounters bad sectors. If a bad sector is found, the drive allocates a sector from the reserve space, and the data is transferred to this new sector.

Notice that for this drive, the RAW_VALUE is 0. Recall that in the Microsoft study, the attribute is important (Table 1, ReallocSectors). Moreover, after the raw count increases, even by 1, the drive has a high probability of failing relatively soon.


Pretty much all drives today come with SMART attributes, and the easy-to-configure Linux smartmontools utilities can query these SMART attributes and perform self-tests. However, because SMART attributes are not standard, smartmontools might not be useful for your particular drive (or RAID card), so you should check on the smartmontools mailing list whether your drive is in the database.

A couple of studies have shown that SMART attributes alone cannot predict the failure of drives. Nonetheless, these attributes can be used as indicators to help determine the probability of a drive failing.