Technical Information

S.M.A.R.T. Attributes

Smart Errors:

  • (AMNF) Data Address Mark Not Found: During the read sector command, a data address mark was not found after finding the correct ID field for the requested sector (usually a media error or read instability).
  • (TONF) Track 0 Not Found: Track 0 was not found during drive recalibration.
  • (ABRT) Aborted Command: The requested command was aborted due to a device status error.
  • (IDNF) ID Not Found: The required cylinder, head, and sector could not be found, or an ECC error occurred in the ID field.
  • (UNC) Uncorrectable Data: An ECC error in the data field could not be corrected (a media error or read instability).
  • (BBK) Bad Mark Block: A bad sector mark was found in the ID field of the sector or an Interface CRC error occurred.

(This following was copied from the Wikipedia page and is for internal CMS quick reference use only. Any other use - please reference the original Wikipedia page)

The following chart lists some S.M.A.R.T. attributes and the typical meaning of their raw values. Normalized values are always mapped so that higher values are better (with only very rare exceptions such as the "Temperature" attribute on certain Seagate drives), but higher raw attribute values may be better or worse depending on the attribute and manufacturer. For example, the "Reallocated Sectors Count" attribute's normalized value decreases as the number of reallocated sectors increases. In this case, the attribute's raw value will often indicate the actual number of sectors that were reallocated, although vendors are in no way required to adhere to this convention. As manufacturers do not necessarily agree on precise attribute definitions and measurement units, the following list of attributes should be regarded as a general guide only.

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Higher raw value is better
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Lower raw value is better
Critical - red colored row
Potential indicators of imminent electromechanical failure


IDHexAttribute nameBetterDescription
01 01 Read Error Rate   Indicates the rate of hardware read errors that occurred when reading data from a disk surface. The raw value has different structure for different vendors and is often not meaningful as a decimal number.
02 02 Throughput Performance
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Overall (general) throughput performance of a hard disk drive. If the value of this attribute is decreasing there is a high probability that there is a problem with the disk.
03 03 Spin-Up Time
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Average time of spindle spin up (from zero RPM to fully operational [millisecs]).
04 04 Start/Stop Count   A tally of spindle start/stop cycles. The spindle turns on, and hence the count is increased, both when the hard disk is turned on after having before been turned entirely off (disconnected from power source) and when the hard disk returns from having previously been put to sleep mode.[13]
05 05 Reallocated Sectors Count
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Count of reallocated sectors. When the hard drive finds a read/write/verification error, it marks this sector as "reallocated" and transfers data to a special reserved area (spare area). This process is also known as remapping, and "reallocated" sectors are called remaps. This is why, on modern hard disks, "bad blocks" cannot be found while testing the surface – all bad blocks are hidden in reallocated sectors. However, as the number of reallocated sectors increases, the read/write speed tends to decrease. The raw value normally represents a count of the number of bad sectors that have been found and remapped. Thus, the higher the attribute value, the more sectors the drive has had to reallocate.
06 06 Read Channel Margin   Margin of a channel while reading data. The function of this attribute is not specified.
07 07 Seek Error Rate   Rate of seek errors of the magnetic heads. If there is a partial failure in the mechanical positioning system, then seek errors will arise. Such a failure may be due to numerous factors, such as damage to a servo, or thermal widening of the hard disk. The raw value has different structure for different vendors and is often not meaningful as a decimal number.
08 08 Seek Time Performance
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Average performance of seek operations of the magnetic heads. If this attribute is decreasing, it is a sign of problems in the mechanical subsystem.
09 09 Power-On Hours (POH)
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Count of hours in power-on state. The raw value of this attribute shows total count of hours (or minutes, or seconds, depending on manufacturer) in power-on state.
10 0A Spin Retry Count
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Count of retry of spin start attempts. This attribute stores a total count of the spin start attempts to reach the fully operational speed (under the condition that the first attempt was unsuccessful). An increase of this attribute value is a sign of problems in the hard disk mechanical subsystem.
11 0B Recalibration Retries
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This attribute indicates the number of times recalibration was requested (under the condition that the first attempt was unsuccessful). An increase of this attribute value is a sign of problems in the hard disk mechanical subsystem.
12 0C Power Cycle Count   This attribute indicates the count of full hard disk power on/off cycles.
13 0D Soft Read Error Rate
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Uncorrected read errors reported to the operating system.
183 B7 SATA Downshift Error Count   Western Digital and Samsung attribute.
184 B8 End-to-End error
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This attribute is a part of HP's SMART IV technology and it means that after transferring through the cache RAM data buffer the parity data between the host and the hard drive did not match.
185 B9 Head Stability   Western Digital attribute.
186 BA Induced Op-Vibration Detection   Western Digital attribute.
187 BB Reported Uncorrectable Errors
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A number of errors that could not be recovered using hardware ECC (see attribute 195).
188 BC Command Timeout
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A number of aborted operations due to HDD timeout. Normally this attribute value should be equal to zero and if the value is far above zero, then most likely there will be some serious problems with power supply or an oxidized data cable.
189 BD High Fly Writes
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HDD producers implement a Fly Height Monitor that attempts to provide additional protections for write operations by detecting when a recording head is flying outside its normal operating range. 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.

This feature is implemented in most modern Seagate drives and some of Western Digital’s drives, beginning with the WD Enterprise WDE18300 and WDE9180 Ultra2 SCSI hard drives, and will be included on all future WD Enterprise products.[14]

190 BE Airflow Temperature (WDC)
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Airflow temperature on Western Digital HDs (Same as temp. [C2], but current value is 50 less for some models. Marked as obsolete.)
190 BE Temperature Difference from 100
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Value is equal to (100 – temp. °C), allowing manufacturer to set a minimum threshold which corresponds to a maximum temperature.

(Seagate only?)
Seagate ST910021AS: Verified Present
Seagate ST9120823ASG: Verified Present under name "Airflow Temperature Cel" 2008-10-06
Seagate ST3802110A: Verified Present 2007-02-13
Seagate ST980825AS: Verified Present 2007-04-05
Seagate ST3320620AS: Verified Present 2007-04-23
Seagate ST3500641AS: Verified Present 2007-06-12
Seagate ST3250824AS: Verified Present 2007-08-07
Seagate ST3250620AS: Verified Present
Seagate ST31000340AS: Verified Present 2008-02-05
Seagate ST31000333AS: Verified Present 2008-11-24
Seagate ST3160211AS: Verified Present 2008-06-12
Seagate ST3320620AS: Verified Present 2008-06-12
Seagate ST3400620AS: Verified Present 2008-06-12
Seagate ST3750330AS: Verified present 2009-07-06
Samsung HD501LJ: Verified Present under name "Airflow Temperature" 2008-03-02
Samsung HD753LJ: Verified Present under name "Airflow Temperature" 2008-07-15

191 BF G-sense error rate
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The number of errors resulting from externally-induced shock & vibration.
192 C0 Power-off Retract Count
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Number of times the heads are loaded off the media. Heads can be unloaded without actually powering off. (or Emergency Retract Cycle count – Fujitsu)
193 C1 Load Cycle Count
Load/Unload Cycle Count
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Count of load/unload cycles into head landing zone position.

The typical lifetime rating for laptop (2.5-in) hard drives is 200,000 to 600,000 load cycles.

Some laptop drives are programmed to unload the heads whenever there has not been any activity for about five seconds. Many Linux installations write to the filesystem a few times a minute in the background. As a result, there may be 100 or more load cycles per hour, and the load cycle rating may be exceeded in less than a year.

194 C2 Temperature
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Current internal temperature.
195 C3 Hardware ECC Recovered   The raw value has different structure for different vendors and is often not meaningful as a decimal number.
196 C4 Reallocation Event Count
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Count of remap operations. The raw value of this attribute shows the total number of attempts to transfer data from reallocated sectors to a spare area. Both successful & unsuccessful attempts are counted.
197 C5 Current Pending Sector Count
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Number of "unstable" sectors (waiting to be remapped, because of read errors). If an unstable sector is subsequently written or read successfully, this value is decreased and the sector is not remapped. Read errors on a sector will not remap the sector (since it might be readable later); instead, the drive firmware remembers that the sector needs to be remapped, and remaps it the next time it's written.
198 C6 Uncorrectable Sector Count
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The total number of uncorrectable errors when reading/writing a sector. A rise in the value of this attribute indicates defects of the disk surface and/or problems in the mechanical subsystem. (or Off-Line Scan Uncorrectable Sector Count – Fujitsu)
199 C7 UltraDMA CRC Error Count
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The number of errors in data transfer via the interface cable as determined by ICRC (Interface Cyclic Redundancy Check).
200 C8 Write Error Rate /
Multi-Zone Error Rate
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The total number of errors when writing a sector.
201 C9 Soft Read Error Rate
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Number of off-track errors.
202 CA Data Address Mark errors
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Number of Data Address Mark errors (or vendor-specific).
203 CB Run Out Cancel
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Number of ECC errors
204 CC Soft ECC Correction
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Number of errors corrected by software ECC
205 CD Thermal Asperity Rate (TAR)
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Number of errors due to high temperaure.
206 CE Flying Height   Height of heads above the disk surface. A flying height that's too low increases the chances of a head crash while a flying height that's too high increases the chances of a read/write error.
207 CF Spin High Current
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Amount of surge current used to spin up the drive.
208 D0 Spin Buzz   Number of buzz routines needed to spin up the drive due to insufficient power.
209 D1 Offline Seek Performance   Drive’s seek performance during its internal tests.
211 D3 Vibration During Write   Vibration During Write
212 D4 Shock During Write   Shock During Write
220 DC Disk Shift
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Distance the disk has shifted relative to the spindle (usually due to shock or temperature). Unit of measure is unknown.
221 DD G-Sense Error Rate
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The number of errors resulting from externally-induced shock & vibration.
222 DE Loaded Hours   Time spent operating under data load (movement of magnetic head armature)
223 DF Load/Unload Retry Count   Number of times head changes position.
224 E0 Load Friction
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Resistance caused by friction in mechanical parts while operating.
225 E1 Load/Unload Cycle Count
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Total number of load cycles
226 E2 Load 'In'-time   Total time of loading on the magnetic heads actuator (time not spent in parking area).
227 E3 Torque Amplification Count
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Number of attempts to compensate for platter speed variations
228 E4 Power-Off Retract Cycle
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The number of times the magnetic armature was retracted automatically as a result of cutting power.
230 E6 GMR Head Amplitude   Amplitude of "thrashing" (distance of repetitive forward/reverse head motion)
231 E7 Temperature
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Drive Temperature
240 F0 Head Flying Hours   Time while head is positioning
240 F0 Transfer Error Rate (Fujitsu)   Counts the number of times the link is reset during a data transfer.
241 F1 Total LBAs Written   Total LBAs Written
242 F2 Total LBAs Read   Total LBAs Read
Some S.M.A.R.T. utilities will report a negative number for the raw value. This is because the author does not understand that attribute values span 48 bits rather than 32.
250 FA Read Error Retry Rate
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Number of errors while reading from a disk
254 FE Free Fall Protection
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Number of "Free Fall Events" detected
Last modified on Tuesday, 14 October 2014 17:25

The DHCP Lease Process


  1. DHCP discovery
    The client broadcasts messages on the physical subnet to discover available DHCP servers. Network administrators can configure a local router to forward DHCP packets to a DHCP server from a different subnet
  2. DHCP offer
    When a DHCP server receives an IP lease request from a client, it reserves an IP address for the client and extends an IP lease offer by sending a DHCPOFFER message to the client. This message contains the client's MAC address, the IP address that the server is offering, the subnet mask, the lease duration, and the IP address of the DHCP server making the offer.
  3. DHCP request
    In response to the offer Client requests the server. The client replies DHCPRequest, unicast to the server, requesting the offered address. A client can receive DHCP offers from multiple servers, but it will accept only one DHCP offer. Based on the Transaction ID field in the request, servers are informed whose offer the client has accepted. When other DHCP servers receive this message, they withdraw any offers that they might have made to the client and return the offered address to the pool of available addresses. In some cases DHCP request message is broadcast, instead of being unicast to a particular DHCP server, because the DHCP client has still not received an IP address. Also, this way one message can let all other DHCP servers know that another server will be supplying the IP address without missing any of the servers with a series of unicast messages.
  4. DHCP acknowledgement
    When the DHCP server receives the DHCPREQUEST message from the client, the configuration process enters its final phase. The acknowledgement phase involves sending a DHCPACK packet to the client. This packet includes the lease duration and any other configuration information that the client might have requested. At this point, the IP configuration process is completed.
  • DHCP information
    A DHCP client may request more information than the server sent with the original DHCPOFFER. The client may also request repeat data for a particular application. For example, browsers use DHCP Inform to obtain web proxy settings via WPAD. Such queries do not cause the DHCP server to refresh the IP expiry time in its database.
  • DHCP releasing
    The client sends a request to the DHCP server to release the DHCP information and the client deactivates its IP address. As client devices usually do not know when users may unplug them from the network, the protocol does not mandate the sending of DHCP Release.


DHCP MessageDescription
DHCP Discover UDP broadcast from DHCP client to locate available servers.
DHCP Offer DHCP server to client in response to DHCP Discover with offer of configuration parameters.
DHCP Request Client response to servers either requesting offered parameters from one server and implicitly declining offers from all others, confirming correctness of previously allocated address after, e.g. system reboot, or extending the lease on a particular network address.
DHCP ACK Server to client with configuration parameters, including committed network address.
DHCP NAK Server to client indicating client’s notion of network address is incorrect (e.g. client has moved to new subnet) or client’s lease has expired.
DHCP Decline Error message from DHCP client to server indicating network address is already in use.
DHCP Release Message from DHCP client to server releasing network address and canceling remaining lease.
DHCP Inform Client asking DHCP server only for local configuration parameters because the client already has externally configured network address.
Last modified on Monday, 12 January 2015 18:42