S.M.A.R.T or SMART is a monitoring system built into the majority of modern disk drives. It is very useful to monitor drive health and predict failures.
In order to fully take advantage of SMART on a unix-based system, we will be using an open source tool suite called smartmontools which contains the
smartctl utility. You can install it on FreeBSD using:
pkg install smartmontools
smartctl executable is found under the
sbin folder, as it is meant for administrative purposes. When using
smartctl, you should run it under the
I will only be dealing with ATA devices for this post (as it’s the only type I own), so I’ll be excluding any SCSI or NVMe specific info. Additionally, I am using smartmontools 6.6 on FreeBSD.
According to the manpage
smartctl is a “Control and Monitor Utility for SMART Disks”. As always, the manpage is the best place to find a full list of features and descriptions:
However, we will go through few examples and explanations of common commands to get started.
--scan flag is useful for finding the drives attached to your system.
The output shows I have two disk devices,
--info flag provides some useful details about your drive.
smartctl -i /dev/ada0
Here is the output that I get on my system:
Model Family: Hitachi/HGST Ultrastar 7K4000 Device Model: HGST HUS724020ALA640 Serial Number: PN1134P6HHPTXN LU WWN Device Id: 5 000cca 22dd53aeb Firmware Version: MF6OABY0 User Capacity: 2,000,398,934,016 bytes [2.00 TB] Sector Size: 512 bytes logical/physical Rotation Rate: 7200 rpm Form Factor: 3.5 inches Device is: In smartctl database [for details use: -P show] ATA Version is: ATA8-ACS T13/1699-D revision 4 SATA Version is: SATA 3.0, 6.0 Gb/s (current: 3.0 Gb/s) Local Time is: Fri Jan 18 10:40:53 2019 EST SMART support is: Available - device has SMART capability. SMART support is: Enabled
Notice that SMART is available and enabled on this drive. If it is not enabled, you can run the
-s on or
--smart=on flag to enable it.
smartctl -s on /dev/ada0
--health flag provides a quick status (pass/fail) on your drive:
smartctl -H /dev/ada0
If this command reports a failing health status, then either the device has already failed or its predicted failure is within 24 hours. You should take immediate action if this is the case.
On FreeBSD, you can add the following lines to your
/etc/periodic.conf to enable a daily health check of your drives:
daily_status_smart_enable="YES" daily_status_smart_devices="ada0 ada1"
--attributes flag provides a set of vendor-defined attributes and their values. These attributes help determine and predict the drives likelihood to fail and its age. It is much more detailed than the health command.
smartctl -A /dev/ada0
Here are my devices attributes:
ID# ATTRIBUTE_NAME FLAG VALUE WORST THRESH TYPE UPDATED WHEN_FAILED RAW_VALUE 1 Raw_Read_Error_Rate 0x000b 100 100 016 Pre-fail Always - 0 2 Throughput_Performance 0x0005 137 137 054 Pre-fail Offline - 78 3 Spin_Up_Time 0x0007 135 135 024 Pre-fail Always - 460 (Average 461) 4 Start_Stop_Count 0x0012 100 100 000 Old_age Always - 108 5 Reallocated_Sector_Ct 0x0033 100 100 005 Pre-fail Always - 0 7 Seek_Error_Rate 0x000b 100 100 067 Pre-fail Always - 0 8 Seek_Time_Performance 0x0005 142 142 020 Pre-fail Offline - 25 9 Power_On_Hours 0x0012 095 095 000 Old_age Always - 40701 10 Spin_Retry_Count 0x0013 100 100 060 Pre-fail Always - 0 12 Power_Cycle_Count 0x0032 100 100 000 Old_age Always - 107 192 Power-Off_Retract_Count 0x0032 100 100 000 Old_age Always - 378 193 Load_Cycle_Count 0x0012 100 100 000 Old_age Always - 378 194 Temperature_Celsius 0x0002 181 181 000 Old_age Always - 33 (Min/Max 18/48) 196 Reallocated_Event_Count 0x0032 100 100 000 Old_age Always - 0 197 Current_Pending_Sector 0x0022 100 100 000 Old_age Always - 0 198 Offline_Uncorrectable 0x0008 100 100 000 Old_age Offline - 0 199 UDMA_CRC_Error_Count 0x000a 200 200 000 Old_age Always - 0
There is a lot of information to digest here, so we’ll go through each tag to form a better understanding (it’s not exactly intuitive).
ID# ATTRIBUTE_NAME FLAG VALUE WORST THRESH TYPE UPDATED WHEN_FAILED RAW_VALUE 194 Temperature_Celsius 0x0002 181 181 000 Old_age Always - 33 (Min/Max 18/48)SMART attributes are given an
ID#from 1 to 253, and are described by and
ATTRIBUTE_NAME. For example, Attribute 194 provides the temperature (in Celsius) of the disk. Wikipedia provides a decent list of common attributes and their descriptions.
ID# ATTRIBUTE_NAME FLAG VALUE WORST THRESH TYPE UPDATED WHEN_FAILED RAW_VALUE 194 Temperature_Celsius 0x0002 181 181 000 Old_age Always - 33 (Min/Max 18/48)The
RAW_VALUEis the “actual” value of the attribute, for example this disk has a temperature of 33 degrees Celsius. This value is then converted by the disks firmware (not
smartctl) to a “normalized”
VALUEfrom 1-254 (1 is the worst, 254 is the best), which helps determine the state of the disk against a vendor provided threshold. The temperature of the disk is not in fact 181 degrees. The
WORSTvalue is the lowest or “worst”
VALUEthat has occurred in the past.
ID# ATTRIBUTE_NAME FLAG VALUE WORST THRESH TYPE UPDATED WHEN_FAILED RAW_VALUE 194 Temperature_Celsius 0x0002 181 181 000 Old_age Always - 33 (Min/Max 18/48)If the normalized
VALUEis less than or equal to the threshold value
THRESH, than the attribute has failed and its
WHEN_FAILEDvalue will read
FAILING_NOW. When the
WORSTvalue is less than or equal to
THRESH, then the attribute has failed previously and its
WHEN_FAILEDvalue will read
In_the_past. Otherwise, it will read
-(which is the ideal value).
TYPEvalues for attributes:
- A failed
Pre-failattribute suggests pending drive failure.
Old_ageattributes indicate the aging and wear out of the disk. A failed
Old_ageattribute suggests the project is reaching its end-of-life.
UPDATEDvalues which indicate when the attribute is updated.
Always: Updated during normal operation.
Offline: Updated during an “offline” test.
FLAG. They describe various properties about each attribute. To get a more readable view of the flags, we can run:
smartctl -A /dev/ada0 -f brief
Which provides this output (
-f brief typically has a <80 character column width)
ID# ATTRIBUTE_NAME FLAGS VALUE WORST THRESH FAIL RAW_VALUE 1 Raw_Read_Error_Rate PO-R-- 100 100 016 - 0 2 Throughput_Performance P-S--- 137 137 054 - 78 3 Spin_Up_Time POS--- 135 135 024 - 460 (Average 461) 4 Start_Stop_Count -O--C- 100 100 000 - 108 5 Reallocated_Sector_Ct PO--CK 100 100 005 - 0 7 Seek_Error_Rate PO-R-- 100 100 067 - 0 8 Seek_Time_Performance P-S--- 142 142 020 - 25 9 Power_On_Hours -O--C- 095 095 000 - 40701 10 Spin_Retry_Count PO--C- 100 100 060 - 0 12 Power_Cycle_Count -O--CK 100 100 000 - 107 192 Power-Off_Retract_Count -O--CK 100 100 000 - 378 193 Load_Cycle_Count -O--C- 100 100 000 - 378 194 Temperature_Celsius -O---- 181 181 000 - 30 (Min/Max 18/48) 196 Reallocated_Event_Count -O--CK 100 100 000 - 0 197 Current_Pending_Sector -O---K 100 100 000 - 0 198 Offline_Uncorrectable ---R-- 100 100 000 - 0 199 UDMA_CRC_Error_Count -O-R-- 200 200 000 - 0 ||||||_ K auto-keep |||||__ C event count ||||___ R error rate |||____ S speed/performance ||_____ O updated online |______ P prefailure warning
These flags are vendor specific, although according to smartmontool’s sourcecode these are “(probably) IBM’s, Maxtors and Quantum’s definitions for the vendor-specific bits”. If the following flag exists for a given attribute, according to smartlinux it most likely means that:
K: The attribute is “self-preserving” and is restored each time when performing a test.
C: Counts events.
R: Measures error rates.
S: Indicates the degradation of speed/performance.
--capabilities flag prints out what SMART features are implemented for this device and how it might react to different SMART commands.
smartctl -c /dev/ada0
Here are the capabilities that my device supports:
Offline data collection status: (0x84) Offline data collection activity was suspended by an interrupting command from host. Auto Offline Data Collection: Enabled. 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: ( 28) seconds. Offline data collection capabilities: (0x5b) SMART execute Offline immediate. Auto Offline data collection on/off support. Suspend 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: ( 1) minutes. Extended self-test routine recommended polling time: ( 321) minutes. SCT capabilities: (0x003d) SCT Status supported. SCT Error Recovery Control supported. SCT Feature Control supported. SCT Data Table supported.
Notice that “Auto Offline Data Collection” is enabled on my drive. This schedules the automatic offline collection of data to be done every four hours, and is useful when the drive has some attributes that are only updated during offline tests. This type of test can technically degrade the performance of the drive, although it is typically only run during periods where the drive is idle. It can be enabled using the
-o VALUE or
smartctl -o on /dev/ada0
SMART supports running a variety of tests with varying degrees of depth. With the exception of the “offline test”, they check the electrical, mechanical and read/write performance of the disk. These can be run using the
This runs the “Offline” test immediately which updates offline attributes. It is not logged like the other tests.
smartctl -t offline /dev/ada0
Short Self Test
This test is a short and less thorough version of the self-test. It typically runs in less than ten minutes although it varies by drive. You can find out how long it should take by checking the drives capabilities using the
-c flag. My drive has a short-test time of 1 minutes.
smartctl -t short /dev/ada0
Extended Self Test
This is the most thorough version of the self-test. It can take tens of minutes to several hours depending on the size and speed of the drive. Again, you can find out how long it should take by checking the drives capabilities using the
-c flag. My drive has a extended-test time of 321 minutes (roughly 5 hours).
smartctl -t long /dev/ada0
Selective Self Test
This test essentially runs the extended test but only on a user defined range of logical block addresses. These are particularly useful for large disks (where extended tests take several hours) or if you suspect a disk is having problems at a particular address. You can run up to five selective tests at once. A full description of the range syntax you can use for the
select command can be found under the
--test section of the manpage.
smartctl -t select,0-1000 -t select,5000-6000 /dev/ada0
Disks with SMART support keep logs containing errors, test results, temperature history and more. A comprehensive and detailed list can be found under the
--log section of the
You can list the five most recent SMART errors by using the
-l error or
smartctl -l error /dev/ada0
You can list the most recent selftests along with their status and age:
smartctl -l selftest /dev/ada0
Here is what my output looks like:
Num Test_Description Status Remaining LifeTime(hours) LBA_of_first_error # 1 Selective offline Completed without error 00% 40796 - # 2 Short offline Completed without error 00% 40796 -
LBA_of_first_error contains a number value, then that is the first block that contains an error. Smartmontools provides a comprehensive article on how to approach these errors.
Selective Selftest Description
This command displays the start/end logical block addresses for each of the five test spans and their status for the most recent selective selftest.
smartctl -l selective /dev/ada0
This is the log for the selective test I ran here:
SPAN MIN_LBA MAX_LBA CURRENT_TEST_STATUS 1 0 1000 Not_testing 2 5000 6000 Not_testing 3 0 0 Not_testing 4 0 0 Not_testing 5 0 0 Not_testing
smartctl provides an insane amount of functionality and is quite useful for monitoring drive health. Although I haven’t outlined all of
smartctl, this is enough to run a few tests and understand the
--all flag, as
-a is equivalent to:
-l error: Error Log
-l selftest: Selftest Log
-l selective: Selective Selftest Log
smartctl -a /dev/ada0
As you can probably guess, regularly scheduling tests and scanning for errors can be quite useful. That is where
smartd comes into play, which you can read more about in my post “Using smartd”.