1        编写目的
在如今大数据的环境中，磁盘的性能和稳定性是非常重要的一个业务因素。在Linux系统中，smartctl是较为常用的磁盘检测工具。
本文基于Linux系统中smartctl进行分析，目的在于说明相关工具的使用，并对SMART(Self-Monitoring, Analysis and Reporting Technology)做一些分析。
2        术语、定义和缩略语
2.1        术语、定义
本文使用的专用术语、定义，见表2.1。
表2.1
术语/定义        含义
SMART        Self-Monitoring, Analysis and Reporting Technology
2.2        缩略语
本文件应用了以下缩略语，见表2.2。
表2.2
缩略语        原    文        中文含义
SMART        Self-Monitoring, Analysis and Reporting Technology        自监察分析及报告技术
               
               
3        smartctl
smartctl是smartmontools-5.38-2.el5 rpm中的一个命令行工具，可以执行SMART任务：打印SMART self-test和error报告，开启或关闭SMART自动测试，触发磁盘self-test。
语法：
       smartctl  [options]  device
device：
"/dev/hd[a-t]"    IDE/ATA 磁盘
"/dev/sd[a-z]"    SCSI devices磁盘。注意，对于SATA磁盘，由于是通过libata
库来访问，所以要增加参数"-d  ata"。
3.1        [options]：
        参数按照不同的类型来分类。
3.1.1        显示信息 参数：
-h                帮助信息
-V                版本信息
-i                打印基本信息（磁盘设备号、序列号、固件版本…）
-a      打印磁盘所有的SMART信息
3.1.2        运行时行为 参数：
-q  TYPE        指定输出的安静模式。
TYPE可以有3种选择：
                          eorsonly                只打印错误日志。
                          slent                        有任何打印。
                          nserial                不打印序列号
        -d  TYPE        指定磁盘的类型。如果没有指定，smartctl会根据磁盘的名字来
猜测磁盘类型。
-T  TYPE        指定当发生错误时，smartctl的容忍程度，是否继续运行。
                        TYPE可以有4种选择：
                          conservative        一有错就会退出
                          normal        如果必须支持的SMART命令失败，则退出
                          permissive     忽略一次必须支持的SMART命令失败
                          verypermissive  忽略所有必须支持的SMART命令失败
-b  TYPE        指定当发生校验错误时，smartctl的动作。
                        TYPE有3种选择：
                          warn                发出警告，继续执行
                          exit                 退出smartctl
                          ignore                不发出告警，继续执行       
-r  TYPE        smartmontools开发人员相关。
-n  POWERMODE        指定当磁盘处于节能模式时，smartctl是否继续检查，
默认是不检查。
POWERMODE有4种选择：
  never   检查
  sleep    除了sleep模式，检查。
  standby  除了sleep或standby模式，检查。
  idle      除了sleep或standby或idle模式，见车。
3.1.3        SMART功能开关 参数：
-s  on/off        打开或关闭磁盘的SMART功能
-o  on/off        打开或关闭SMART自动离线检测，该功能每4小时就会自动扫描磁盘是
否有缺陷。
-S  on/off   打开或关闭“自动保存厂商指定属性”功能。
3.1.4        SMART 读和显示数据 参数
-H                报告磁盘的是否健康。如果报告不健康，则说明磁盘已经损坏或会在24小时
内损坏。
-c                显示磁盘支持的普通SMART功能，以及这些功能当前的状态。
-A                显示磁盘支持的厂商指定SMART特性。这些特性的编号从1-253，并且有指
定的名字。
-l  TYPE        指定显示的log类型。
                        TYPE有4种选择：
                        error                只显示error  log。
                        selftest        只显示selftest  log
                        selective 只显示selective  self-test  log
                        directory 只显示Log  Directory
        -v  N,OPTION        显示厂商指定SMART特性N时，使用厂商相关的显示方式。
-F  TYPE        设置smartctl的行为，当出现一些已知但还没有解决的硬件或软件bug时，
smartctl应该怎么做。
-P  TYPE        设置smartctl是否对磁盘使用数据库中已有的参数。
3.1.5        SMART 离线测试、自测试 参数
-t  TEST        立刻执行测试，可以和-C参数一起使用。
                        TEST可以有以下几个选择：
                        offline  离线测试。可以在挂载文件系统的磁盘上使用
                        short   短时间测试。可以在挂载文件系统的磁盘上使用。
                        long   长时间测试。可以在挂载文件系统的磁盘上使用。
                        conveyance  [ATA only]传输zi测试。可以在挂载文件系统的磁盘上使用。
                        select, N-M       
select, N+SIZE  [ATA only]有选择性测试，测试磁盘的部分LBA。N表示
LBA编号，M表示结束LBA编号，SIZE表示测试的LBA
范围。
-C  在captive模式下运行测试。
注意：（1）-C必须配合-t一起使用，但如果是-t offline，则-C不生效。
         （2）-C会使得磁盘很忙，所以最好是在没有挂载文件系统的磁盘上使用。
-X  中断no-captive模式下运行的测试。
3.2        常用example
3.2.1        查看当前整体健康状态
查看/dev/sda当前整体监控状态。PASSED表示健康，否则意味着磁盘已经故障，或很快就会发生故障。
smartctl  -H  /dev/sda

3.2.2        查看所有信息
打印/dev/sda所有的SMART信息。
martctl  -a  /dev/sda

相当于依次执行：
smartctl  –i  /dev/sda   
smartctl  -c  /dev/sda   
smartctl  -A  /dev/sda   
smartctl  -l  error  /dev/sda
smartctl  -l  selftest  /dev/sda
smartctl  -l  selective  /dev/sda
3.2.3        开/关SMART功能
打开或关闭/dev/sda 的SMART功能。
smartctl  -s  on/off  /dev/sda

查看当前SMART功能是否开启，可以使用 –i 参数。
smartctl  -i  /dev/sda
3.2.4        离线测试
对/dev/sda进行离线测试，它的结果主要用来更新SMART 属性。
smartctl  -t  offline  /dev/sda
3.2.5         短时间测试
对/dev/sda进行短时间测试。
smartctl  -t  short  /dev/sda
3.2.5.1        观察测试进度
通过-c 参数，可以观察到测试的进度：
# smartctl -c    /dev/sda
…
Self-test execution status:      ( 242)        Self-test routine in progress...
                                                    20% of test remaining.
…
3.2.5.2        观察测试结果
通过-l selftest 参数，可以看到/dev/sda测试的结果记录：
“#1”代表的那一次测试，Completed without error表示完成，没有错误。
“#2”代表的那一次测试，Aborted by host表示测试被用户终止，还有90%没有完成。

# smartctl -l selftest    /dev/sda
...
Num  Test_Description  Status                  Remaining  LifeTime(hours)  LBA_of_first_error
# 1  Short offline       Completed without error   00%        9535         -
# 2  Extended offline    Aborted by host          90%        9534         -
...
3.2.6        查看SMART属性值
通过-A参数，可以看到/dev/sda SMART属性值。
smartctl  -A  /dev/sda

每一行代表一个SMART属性的相关信息。
RAW_VALUE: 表示该属性的实际值，比如12行，表示磁盘power-cycle的实际次数。
VALUE: 范围是1到254，由RAW_VALUE装换而来，装换工作是由磁盘的固件自己完成的。
THRESH: 范围0到255，门限值，和VALUE值比较。如果VALUE值小于等于THRESH，那么这个属性就不正常了。
TYPE: Pre-fail表示当VALUE值小于或等于THRESH时，磁盘即将会有相关故障。
      Old_age表示当VALUE值小于或等于THRESH时，磁盘相关属性已经老化。
3.3        smartctl结构
smartctl工具的主要结构如下图，解析参数后，就根据参数指定的值设置或查询SMART信息。

3.4        SMART 属性
使用smartctl  -A  /dev/sda能看到很多磁盘的SMART        属性，可以知道磁盘是否健康。
下面是一个列表，可以知道每个属性的具体含义：
ID        Hex        Attribut name        Description
01        0x01        Read Error Rate        (Vendor specific raw value.) Stores data related to 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        0x02        Throughput Performance        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        0x03        Spin-Up Time        Average time of spindle spin up (from zero RPM to fully operational [millisecs]).
04        0x04        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.
05        0x05        Reallocated Sectors Count        Count of reallocated sectors. When the hard drive finds a read/write/verification error, it marks that 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". The raw value normally represents a count of the bad sectors that have been found and remapped. Thus, the higher the attribute value, the more sectors the drive has had to reallocate. This allows a drive with bad sectors to continue operation; however, a drive which has had any reallocations at all is significantly more likely to fail in the near future.[2]While primarily used as a metric of the life expectancy of the drive, this number also affects performance. As the count of reallocated sectors increases, the read/write speed tends to become worse because the drive head is forced to seek to the reserved area whenever a remap is accessed. A workaround which will preserve drive speed at the expense of capacity is to create a disk partition over the region which contains remaps and instruct the operating system to not use that partition.
06        0x06        Read Channel Margin        Margin of a channel while reading data. The function of this attribute is not specified.
07        0x07        Seek Error Rate        (Vendor specific raw value.) 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        0x08        Seek Time Performance        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        0x09        Power-On Hours (POH)
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        0x0A        Spin Retry Count        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        0x0B        Recalibration Retries orCalibration Retry Count        This attribute indicates the count that 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        0x0C        Power Cycle Count        This attribute indicates the count of full hard disk power on/off cycles.
13        0x0D        Soft Read Error Rate        Uncorrected read errors reported to the operating system.
180        0xB4        Unused Reserved Block Count Total        "Pre-Fail" Attribute used at least in HP devices.
183        0xB7        SATA Downshift Error Count        Western Digital and Samsung attribute.
184        0xb8        End-to-End error / IOEDC                This attribute is a part of Hewlett-Packard‘s SMART IV technology, as well as part of other vendors‘ IO Error Detection and Correction schemas, and it contains a count of parity errors which occur in the data path to the media via the drive‘s cache RAM.
185        0xB9        Head Stability        Western Digital attribute.
186        0xBA        Induced Op-Vibration Detection        Western Digital attribute.
187        0xBB        Reported Uncorrectable Errors        The count of errors that could not be recovered using hardware ECC .
188        0xBC        Command Timeout        The count 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        0xBD        High Fly Writes        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.

190        0xBE        Airflow Temperature (WDC) resp.Airflow Temperature Celsius (HP)        Airflow temperature on Western Digital HDs (Same as temp. [C2], but current value is 50 less for some models. Marked as obsolete.)
191        0xBF        G-sense Error Rate        The count of errors resulting from externally-induced shock & vibration.
192        0xC0        Power-off Retract Countor Emergency Retract Cycle Count(Fujitsu)        Count of times the heads are loaded off the media. Heads can be unloaded without actually powering off.
193        0xC1        Load Cycle Count orLoad/Unload Cycle Count(Fujitsu)        Count of load/unload cycles into head landing zone position.
The typical lifetime rating for laptop (2.5-in) hard drives is 300,000 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 file system 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        0xC2        Temperatureresp.Temperature Celsius        Current internal temperature.
195        0xC3        Hardware ECC Recovered        (Vendor specific raw value.) The raw value has different structure for different vendors and is often not meaningful as a decimal number.
196        0xC4        Reallocation Event Count        Count of remap operations. The raw value of this attribute shows the total count of attempts to transfer data from reallocated sectors to a spare area. Both successful & unsuccessful attempts are counted.
197        0xC5        Current Pending Sector Count        Count of "unstable" sectors (waiting to be remapped, because of read errors). If an unstable sector is subsequently 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        0xC6        Uncorrectable Sector Countor
Offline Uncorrectableor
Off-Line Scan Uncorrectable Sector Count
        The total count 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.
199        0xC7        UltraDMA CRC Error Count        The count of errors in data transfer via the interface cable as determined by ICRC (Interface Cyclic Redundancy Check).
200        0xC8        Multi-Zone Error Rate        The count of errors found when writing a sector. The higher the value, the worse the disk‘s mechanical condition is.
200        0xC8        Write Error Rate (Fujitsu)        The total count of errors when writing a sector.
201        0xC9        Soft Read Error Rate or
TA Counter Detected
        Count of off-track errors.
202        0xCA        Data Address Mark errorsor
TA Counter Increased
        Count of Data Address Mark errors (or vendor-specific).
203        0xCB        Run Out Cancel        Count of ECC errors
204        0xCC        Soft ECC Correction        Count of errors corrected by software ECC
205        0xCD        Thermal Asperity Rate (TAR)        Count of errors due to high temperature.
206        0xCE        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        0xCF        Spin High Current        Amount of surge current used to spin up the drive.
208        0xD0        Spin Buzz        Count of buzz routines needed to spin up the drive due to insufficient power.
209        0xD1        Offline Seek Performance        Drive’s seek performance during its internal tests.
210        0xD2        Unkonw        (found in a Maxtor 6B200M0 200GB and Maxtor 2R015H1 15GB disks)
211        0xD3        Vibration During Write        Vibration During Write
212        0xD4        Shock During Write        Shock During Write
220        0xDC        Disk Shift        Distance the disk has shifted relative to the spindle (usually due to shock or temperature). Unit of measure is unknown.
222        0xDE        Loaded Hours        Time spent operating under data load (movement of magnetic head armature)
223        0xDF        Load/Unload Retry Count        Count of times head changes position.
224        0xE0        Load Friction        Resistance caused by friction in mechanical parts while operating.
225        0xE1        Load/Unload Cycle Count        Total count of load cycles
226        0xE2        Load ‘In‘-time        Total time of loading on the magnetic heads actuator (time not spent in parking area).
227        0xE3        Torque Amplification Count        Count of attempts to compensate for platter speed variations
228        0xE4        Power-Off Retract Cycle        The count of times the magnetic armature was retracted automatically as a result of cutting power.
230        0xE6        GMR Head Amplitude        Amplitude of "thrashing" (distance of repetitive forward/reverse head motion)
231        0xE7        Temperature        Drive Temperature
232        0xE8        Endurance Remaining        Number of physical erase cycles completed on the drive as a percentage of the maximum physical erase cycles the drive is designed to endure
232        0xE8        Available Reserved Space        Intel SSD reports the number of available reserved space as a percentage of reserved space in a brand new SSD.
233        0xE9        Power-On Hours        Number of hours elapsed in the power-on state.
233        0xE9        Media Wearout Indicator        Intel SSD reports a normalized value of 100 (when the SSD is new) and declines to a minimum value of 1. It decreases while the NAND erase cycles increase from 0 to the maximum-rated cycles.
240        0xF0        Head Flying Hours        Time while head is positioning
240        0xF0        Transfer Error Rate(Fujitsu)        Count of times the link is reset during a data transfer.
241        0xF1        Total LBAs Written        Total count of LBAs written
242        0xF2        Total LBAs Read        Total count of LBAs read.
Some S.M.A.R.T. utilities will report a negative number for the raw value since in reality it has 48 bits rather than 32.
250        0xFA        Read Error Retry Rate        Count of errors while reading from a disk
254        0xFE        Free Fall Protection        ount of "Free Fall Events" detected

3.5        SMART self-test
使用smartctl  –t  offline/short/long   可以指定磁盘进行自测。
offline：
这个是默认的自测。
short：
        短时自测的目的是快速确认磁盘是否故障。
        测试过程有很多项目，都是磁盘厂商自定义的，比如下面的项目：
a)        电气测试项目，测试磁盘内部的电路。具体测试细节有磁盘厂商自己指定，比如：
A)        缓存测试。
B)        读、写电路测试。
C)        读、写磁头测试。
b)        寻道、伺服测试项目，测试磁盘在数据磁道上的寻找和伺服能。
c)        读、校验测试项目，测试磁盘对部分或全盘的读能力。
long：
        称为扩展的自测试。测试的项目和short类型，但是时间长得多。

SMART 磁盘监控方案