Self-Monitoring, Analysis, and Reporting Technology – S.M.A.R.T.

Hard Disk Sentinel (HDSentinel) is a multi-OS SSD and HDD monitoring and analysis software.

S.M.A.R.T. (often written as SMART) is a monitoring system built in to Hard Disks and SSDs, to detect and report parameters that can help determine a disk’s reliability. Although SMART can help determine a disk’s current state and possibly (future) failures, not all disk failures are predictable. It is important to keep that in mind when interpreting SMART data attributes.

S.M.A.R.T. data is used by:

  • The PC BIOS
  • Windows
  • Utility Software

Use the iRecover SMART window to determine a disk’s condition.

iRecover contains an on-demand S.M.A.R.T. tool that allows you to determine the current state of the disk:

In the ‘Disks and Partitions’ list select a physical disk > Click ‘More Functions’ > Select SMART Information.

S.M.A.R.T. attributes window iRecover

S.M.A.R.T. attributes window iRecover

I have highlighted the important attributes that can be used to examine a disk’s physical condition. High raw values for the ‘Reallocated Sector Count’ and/or ‘Current Pending Sector Count’ are reason for concern and it may be wise to clone or image the disk first. If you want me to help you interpret SMART data, click ‘Save to file’, and email me the file (joep@disktuna.com)

iRecover is a ‘dumb’ SMART data ‘messenger’, it just gets the data and displays it. It does not interpret values, nor does it monitor SMART data over a longer period. It is however useful for quickly determining the physical state of the disk.

Keeping an eye on your hard disk’s health.

Although I try to run as little software in the background as possible (as you may have guessed from the DiskTuna description on this site’s home page), I do make a few exceptions: I run anti virus software and I run a S.M.A.R.T. monitor.

By running a S.M.A.R.T. monitor constantly in the background you will be warned when a disk is (about to be) failing on you. As a SMART monitor is watching the disk over a longer period of time it can even try to make some predictions on when a disk may fail in the future. Also, a program like HD Sentinel can even out-smart the built-in failure prediction of a disk (which is basically nothing more than a ‘pre-fail’ attribute exceeding threshold) based on loads of experience with loads of different hard disks. But again, keep in mind that not all hard disk failures can be predicted!

When a hard disk fails or dies, DIY data recovery is hardly ever an option! If a disk fails and data was not backed up, you almost always have to go the expensive route to recover the data: sent the disk to a data recovery lab.

Utilities that keep an eye on your disk’s health:

HD Sentinel
HD Sentinel info and purchase URL.
HD Sentinel website
Active SMART
Active SMART purchase URL
Active SMART website

 S.M.A.R.T. Attributes

To predict failures and/or to display S.M.A.R.T. information. For example, a PC may warn the user during the boot process that a disk is about to fail and data needs to backed up ASAP. There are numerous utilities available that either run on-demand to display current S.M.A.R.T. data, or that monitor S.M.A.R.T. data all the time while running in the background. S.M.A.R.T. data is typically displayed in an attribute list using columns for the different SMART attributes:

Attribute Value Worst Threshold RAW value
Attribute ID and name The current normalized value for the attribute. 1 generally is worst, 253 best. Worst normalized value that was ever detected. 1 generally is worst, 253 best. The critical value. Once the value is reached the attribute ‘fails’. Note however that not all attributes are ‘pre-fail’ attributes.  The RAW data. So for example, for the attribute ‘Reallocated Sector Count’, the value would display actual number of reallocated sectors.

Attributes are being used to retrieve current psychical/logical state of a drive and to show their meaning in much more readable form for end-user. Threshold is the critical value for an attribute. Any value lower than (or equal to) threshold means decreased performance or even hard disk failure.

SMART utilities can display less or additional columns. Sometimes the RAW value for an attribute is hidden. Many show an extra column displaying ‘OK’ or ‘FAIL’. Thus making it easier to determine which attributes are problematic


Each attribute can have a certain collection of flags:

Flag name Description
Pre-failure warranty attribute (PW) Indicates a pre-failure condition (caused by exceeded threshold) where imminent loss of data is being predicted (life critical attribute).
Online collection attribute (OC) Indicates that the value of this attribute is calculated during Online test.
Performance attribute (PE) Indicates degradation of performance caused by usage or age of a drive.
Error rate attribute (ER) Indicates that attribute measure frequency of errors.
Error count attribute (EC) Indicates that attribute is a counter of events.
Self-preserving attribute (SP) Indicates that attribute is automatically preservable and restored each time when performing S.M.A.R.T. tests.

Known attributes

ID Name of attribute Description
0 ATTR INVALID Invalid attribute
1 Raw Read Error Rate Frequency of errors appearance while reading RAW data from a disk. Lower RAW value is better.
2 Throughput Performance Overall (general) throughput performance of a hard disk drive. Higher RAW value is better.
3 Spin Up Time (ms) Time needed by spindle to spin-up
4 Start/Stop Count Number of start/stop cycles of spindle
5 Reallocated Sector Count Count of reallocated sectors. The raw value normally represents a count of the bad sectors that have been found and remapped
6 Read Channel Margin Reserve of channel while reading
7 Seek Error Rate Frequency of errors appearance while positioning
8 Seek Time Performance The average efficiency of operations while positioning
9 Power-On Count (hrs or min) Quantity of elapsed hours (or minutes) in the switched-on state
10 Spin-up Retry Count Number of attempts to start a spindle of a disk
11 Calibration Retry Count Number of attempts to calibrate a drive
12 Power Cycle Count Number of complete start/stop cycles of hard disk
13 Soft Read Error Rate Frequency of “program” errors appearance while reading data from a disk
22 Current Helium Level Specific to He8 drives from HGST. This value measures the helium inside of the drive specific to this manufacturer
170 Available Reserved Space Number of physical erase cycles completed on the drive as a percentage of the maximum physical erase cycles the drive is designed to endure
171 SSD Program Fail Count (Kingston) The total number of flash program operation failures since the drive was deployed
172 SSD Erase Fail Count (Kingston) Counts the number of flash erase failures
173 SSD Wear Leveling Count Counts the maximum worst erase count on any block
174 Unexpected power loss count Raw value reports the number of unclean shutdowns
175 Power Loss Protection Failure Last test result as microseconds to discharge cap
176 Erase Fail Count S.M.A.R.T. parameter indicates a number of flash erase command failures
177 Wear Range Delta Delta between most-worn and least-worn Flash blocks. It describes how good/bad the wear-leveling of the SSD works on a more technical way
179 Used Reserved Block Count Total Pre-Fail attribute used at least in Samsung devices
180 Unused Reserved Block Count Total Pre-Fail attribute used at least in HP devices
181 Program Fail Count Total Total number of Flash program operation failures since the drive was deployed
182 Erase Fail Count Pre-Fail Attribute used at least in Samsung devices
183 SATA Downshift Error Count Western Digital, Samsung or Seagate attribute: Total number of data blocks with detected, uncorrectable errors encountered during normal operation
184 End-to-End error Count of parity errors which occur in the data path to the media via the drive’s cache RAM
185 Head Stability Western Digital attribute
186 Induced Op-Vibration Detection Western Digital attribute
187 Uncorrectable Errors The count of errors that could not be recovered using hardware ECC
188 Command Timeout The count of aborted operations due to HDD timeout. Normally this attribute value should be equal to zero
189 High Fly Writes If an unsafe fly height condition is encountered, the write process is stopped, and the information is rewritten or reallocated to a safe region of the hard drive. This attribute indicates the count of these errors detected over the lifetime of the drive.
190 Airflow Temperature Airflow temperature on Western Digital HDs
191 G-Sense Error Rate The count of errors resulting from externally induced shock and vibration
192 Power-Off Retract Cycle Number of power-off or emergency retract cycles
193 Load/Unload Cycle Count Count of load/unload cycles into head landing zone position
194 HDA Temperature (°C) Temperature of a Hard Disk Assembly
195 Hardware ECC Recovered Frequency of the on the fly errors (Fujitsu: ECC On The Fly Count)
196 Reallocated Event Count Count of remap operations
197 Current Pending Sector Count Current count of unstable sectors (waiting for remapping)
198 Off-line Scan Uncorrectable Count Count of uncorrected errors
199 UltraDMA CRC Error Rate Total count of errors CRC during UltraDMA mode
200 Write Error Rate Count of errors appearance while recording data into disk (Western Digital: Multi Zone Error Rate)
201 Soft Read Error Rate I Count of the off track errors (Maxtor: Off Track Errors)
202 Data Address Mark Errors Count of the Data Address Mark errors
203 Run Out Cancel Count of the ECC errors (Maxtor: ECC Errors)
204 Soft ECC Correction Count of errors corrected by software ECC
205 Thermal Asperity Rate Count of the thermal asperity errors
206 Flying Height The height of the disk heads above the disk surface
207 Spin High Current Quantity of used high current to spin up drive
208 Spin Buzz Quantity of used buzz routines to spin up drive
209 Offline Seek Performance Drive’s seek performance during offline operations
210 Vibration During Write Found in Maxtor 6B200M0 200GB and Maxtor 2R015H1 15GB disks
211 Vibration During Write A recording of a vibration encountered during write operations
212 Shock During Write A recording of shock encountered during write operations
220 Disk Shift Shift of disk is possible as a result of strong shock loading in the store, as a result of it’s falling or for other reasons (sometimes: Temperature)
221 G-Sense Error Rate II The count of errors resulting from externally induced shock & vibration (dropping drive, for example)
222 Loaded Hours Loading on drive caused by the general operating time of hours it stores
223 Load/Unload Retry Count Loading on drive caused by numerous recurrences of operations like: reading, recording, positioning of heads, etc.
224 Load Friction Loading on drive caused by friction in mechanical parts of the store
225 Load/Unload Cycle Count II Total of cycles of loading on drive
226 Load-in Time General time of loading for drive
227 Torque Amplification Count Quantity efforts of the rotating moment of a drive
228 Power-Off Retract Count Quantity of the fixed turning off’s a drive
230 Drive Life Protection Status Current state of drive operation based upon the Life Curve
231 SSD Life Left Indicates the approximate SSD life left, in terms of program/erase cycles or Flash blocks currently available for use
232 Available Reserved Space Intel SSD reports the number of available reserved space as a percentage of reserved space in a brand new SSD
233 Media Wearout Indicator Intel SSD reports a normalized value of 100 (when the SSD is new) and declines to a minimum value of 1
234 Avg Erase Count AND Max Erase Count Decoded as: byte 0-1-2 = average erase count (big endian) and byte 3-4-5 = max erase count (big endian)
235 Good Block Count Decoded as: byte 0-1-2 = good block count (big endian) and byte 3-4 = system (free) block count
240 Head Flying Hours Time while head is positioning
241 Total LBAs Written Total count of LBAs written
242 Total LBAs Read Total count of LBAs read
243 Total LBAs Written Expanded The upper 5 bytes of the 12-byte total number of LBAs written to the device
244 Total LBAs Read Expanded The upper 5 bytes of the 12-byte total number of LBAs read from the device
249 NAND_Writes_1GiB Total NAND Writes. Raw value reports the number of writes to NAND in 1 GB increments
250 Read Error Retry Rate Count of errors appearance while reading data from a disk