我有一对WDD驱动器，最近有一个被踢出了RAID1arrays。
SMART显示某些扇区存在IO错误，但所有SMART属性看起来都不错：
root@nas:~# smartctl -a /dev/sdb smartctl 6.5 2016-05-07 r4318 [x86_64-linux-4.4.68.x86_64.1] (local build) Copyright (C) 2002-16, Bruce Allen, Christian Franke, www.smartmontools.org === START OF INFORMATION SECTION === Model Family: Western Digital Red Device Model: WDC WD20EFRX-68AX9N0 Serial Number: WD-WMC30xxxxxxxx LU WWN Device Id: 5 0014ee 602ce8a27 Firmware Version: 80.00A80 User Capacity: 2,000,398,934,016 bytes [2.00 TB] Sector Sizes: 512 bytes logical, 4096 bytes physical Device is: In smartctl database [for details use: -P show] ATA Version is: ACS-2 (minor revision not indicated) SATA Version is: SATA 3.0, 6.0 Gb/s (current: 3.0 Gb/s) Local Time is: Tue Sep 19 07:50:28 2017 WEST SMART support is: Available - device has SMART capability. SMART support is: Enabled === START OF READ SMART DATA SECTION === SMART overall-health self-assessment test result: PASSED General SMART Values: Offline data collection status: (0x00) Offline data collection activity was never started. Auto Offline Data Collection: Disabled. Self-test execution status: ( 121) The previous self-test completed having the read element of the test failed. Total time to complete Offline data collection: (26940) seconds. Offline data collection capabilities: (0x7b) SMART execute Offline immediate. Auto Offline data collection on/off support. Suspend Offline collection upon new command. Offline surface scan supported. Self-test supported. 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: ( 272) minutes. Conveyance self-test routine recommended polling time: ( 5) minutes. SCT capabilities: (0x70bd) SCT Status supported. SCT Error Recovery Control supported. SCT Feature Control supported. SCT Data Table supported. SMART Attributes Data Structure revision number: 16 Vendor Specific SMART Attributes with Thresholds: ID# ATTRIBUTE_NAME FLAG VALUE WORST THRESH TYPE UPDATED WHEN_FAILED RAW_VALUE 1 Raw_Read_Error_Rate 0x002f 191 191 051 Pre-fail Always - 110178 3 Spin_Up_Time 0x0027 195 170 021 Pre-fail Always - 3208 4 Start_Stop_Count 0x0032 065 065 000 Old_age Always - 35326 5 Reallocated_Sector_Ct 0x0033 200 200 140 Pre-fail Always - 0 7 Seek_Error_Rate 0x002e 200 200 000 Old_age Always - 0 9 Power_On_Hours 0x0032 042 042 000 Old_age Always - 43024 10 Spin_Retry_Count 0x0032 100 100 000 Old_age Always - 0 11 Calibration_Retry_Count 0x0032 100 253 000 Old_age Always - 0 12 Power_Cycle_Count 0x0032 100 100 000 Old_age Always - 31 192 Power-Off_Retract_Count 0x0032 200 200 000 Old_age Always - 14 193 Load_Cycle_Count 0x0032 189 189 000 Old_age Always - 35311 194 Temperature_Celsius 0x0022 120 103 000 Old_age Always - 27 196 Reallocated_Event_Count 0x0032 200 200 000 Old_age Always - 0 197 Current_Pending_Sector 0x0032 200 200 000 Old_age Always - 0 198 Offline_Uncorrectable 0x0030 100 253 000 Old_age Offline - 0 199 UDMA_CRC_Error_Count 0x0032 200 200 000 Old_age Always - 0 200 Multi_Zone_Error_Rate 0x0008 200 200 000 Old_age Offline - 0 SMART Error Log Version: 1 ATA Error Count: 1 CR = Command Register [HEX] FR = Features Register [HEX] SC = Sector Count Register [HEX] SN = Sector Number Register [HEX] CL = Cylinder Low Register [HEX] CH = Cylinder High Register [HEX] DH = Device/Head Register [HEX] DC = Device Command Register [HEX] ER = Error register [HEX] ST = Status register [HEX] Powered_Up_Time is measured from power on, and printed as DDd+hh:mm:SS.sss where DD=days, hh=hours, mm=minutes, SS=sec, and sss=millisec. It "wraps" after 49.710 days. Error 1 occurred at disk power-on lifetime: 43000 hours (1791 days + 16 hours) When the command that caused the error occurred, the device was active or idle. After command completion occurred, registers were: ER ST SC SN CL CH DH -- -- -- -- -- -- -- 40 51 01 49 00 90 e0 Error: UNC at LBA = 0x00900049 = 9437257 Commands leading to the command that caused the error were: CR FR SC SN CL CH DH DC Powered_Up_Time Command/Feature_Name -- -- -- -- -- -- -- -- ---------------- -------------------- 40 00 01 49 00 90 e0 08 14d+22:24:56.107 READ VERIFY SECTOR(S) SMART Self-test log structure revision number 1 Num Test_Description Status Remaining LifeTime(hours) LBA_of_first_error # 1 Extended offline Completed: read failure 90% 42999 9437257 # 2 Short offline Completed: read failure 40% 42999 9437257 # 3 Extended offline Completed without error 00% 39200 - # 4 Extended offline Completed without error 00% 39033 - # 5 Extended offline Completed without error 00% 38864 - # 6 Extended offline Completed without error 00% 38708 - # 7 Extended offline Completed without error 00% 38540 - # 8 Extended offline Completed without error 00% 38396 - # 9 Short offline Completed without error 00% 0 - SMART Selective self-test log data structure revision number 1 SPAN MIN_LBA MAX_LBA CURRENT_TEST_STATUS 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 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. 所以在9437257有可重现的错误，我可以看到这与dd：
root@nas:~# export i=9437257 root@nas:~# while [ $i -lt 9437280 ]; do echo $i; dd if=/dev/sdb of=/dev/null bs=512 count=1 skip=$i; let i+=1; done 9437257 dd: error reading '/dev/sdb': Input/output error 0+0 records in 0+0 records out 0 bytes copied, 0.325588 s, 0.0 kB/s 9437258 dd: error reading '/dev/sdb': Input/output error 0+0 records in 0+0 records out 0 bytes copied, 0.164007 s, 0.0 kB/s 9437259 dd: error reading '/dev/sdb': Input/output error 0+0 records in 0+0 records out 0 bytes copied, 0.162149 s, 0.0 kB/s 9437260 dd: error reading '/dev/sdb': Input/output error 0+0 records in 0+0 records out 0 bytes copied, 0.161994 s, 0.0 kB/s 9437261 dd: error reading '/dev/sdb': Input/output error 0+0 records in 0+0 records out 0 bytes copied, 0.161854 s, 0.0 kB/s 9437262 dd: error reading '/dev/sdb': Input/output error 0+0 records in 0+0 records out 0 bytes copied, 0.16294 s, 0.0 kB/s 9437263 dd: error reading '/dev/sdb': Input/output error 0+0 records in 0+0 records out 0 bytes copied, 0.161955 s, 0.0 kB/s 9437264 1+0 records in 1+0 records out 512 bytes copied, 0.0212458 s, 24.1 kB/s 9437265 1+0 records in 1+0 records out 512 bytes copied, 0.000336436 s, 1.5 MB/s 9437266 1+0 records in 1+0 records out 512 bytes copied, 0.000300649 s, 1.7 MB/s 9437267 1+0 records in 1+0 records out 512 bytes copied, 0.000284451 s, 1.8 MB/s 9437268 1+0 records in 1+0 records out 512 bytes copied, 0.00031215 s, 1.6 MB/s 9437269 1+0 records in 1+0 records out 512 bytes copied, 0.000287936 s, 1.8 MB/s 9437270 1+0 records in 1+0 records out 512 bytes copied, 0.000302617 s, 1.7 MB/s 9437271 1+0 records in 1+0 records out 512 bytes copied, 0.000294914 s, 1.7 MB/s 9437272 1+0 records in 1+0 records out 512 bytes copied, 0.000713134 s, 718 kB/s 9437273 1+0 records in 1+0 records out 512 bytes copied, 0.000416336 s, 1.2 MB/s 9437274 1+0 records in 1+0 records out 512 bytes copied, 0.000289526 s, 1.8 MB/s 9437275 1+0 records in 1+0 records out 512 bytes copied, 0.000300769 s, 1.7 MB/s 9437276 1+0 records in 1+0 records out 512 bytes copied, 0.000294524 s, 1.7 MB/s 9437277 1+0 records in 1+0 records out 512 bytes copied, 0.000295592 s, 1.7 MB/s 9437278 1+0 records in 1+0 records out 512 bytes copied, 0.00034751 s, 1.5 MB/s 9437279 1+0 records in 1+0 records out 512 bytes copied, 0.000301789 s, 1.7 MB/s root@nas:~#
我试图写这些部门，让他们重新分配，但我只是得到更多的错误：
root@nas:~# dd if=/dev/zero of=/dev/sdb bs=512 count=7 seek=9437257 dd: error writing '/dev/sdb': Input/output error 1+0 records in 0+0 records out 0 bytes copied, 0.168565 s, 0.0 kB/s root@nas:~#
我也试过sg_verify和sg_reassign：
root@nas:~# sg_verify /dev/sdb --lba=9437257 verify (10): Descriptor format, current; Sense key: Medium Error Additional sense: Unrecovered read error - auto reallocate failed Descriptor type: Information: 0x0000000000900049 VERIFY(10) medium or hardware error, reported lba=0x900049 root@nas:~# sg_reassign --address=9437257 /dev/sdb REASSIGN BLOCKS: Illegal request, invalid opcode
journalctl中还有很多噪音：
Sep 19 07:58:26 nas kernel: ata2.00: configured for UDMA/133 Sep 19 07:58:26 nas kernel: sd 1:0:0:0: [sdb] tag#12 FAILED Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE Sep 19 07:58:26 nas kernel: sd 1:0:0:0: [sdb] tag#12 Sense Key : Medium Error [current] [descriptor] Sep 19 07:58:26 nas kernel: sd 1:0:0:0: [sdb] tag#12 Add. Sense: Unrecovered read error - auto reallocate failed Sep 19 07:58:26 nas kernel: sd 1:0:0:0: [sdb] tag#12 CDB: Read(10) 28 00 00 90 00 49 00 00 01 00 Sep 19 07:58:26 nas kernel: blk_update_request: I/O error, dev sdb, sector 9437257 Sep 19 07:58:26 nas kernel: Buffer I/O error on dev sdb3, logical block 9, async page read Sep 19 07:58:26 nas kernel: ata2: EH complete Sep 19 07:58:26 nas kernel: ata2.00: exception Emask 0x0 SAct 0x1f800000 SErr 0x0 action 0x0 Sep 19 07:58:26 nas kernel: ata2.00: irq_stat 0x40000008 Sep 19 07:58:26 nas kernel: ata2.00: failed command: READ FPDMA QUEUED Sep 19 07:58:26 nas kernel: ata2.00: cmd 60/01:e0:4a:00:90/00:00:00:00:00/40 tag 28 ncq 512 in res 41/40:00:4a:00:90/00:00:00:00:00/40 Emask 0x409 (media error) <F> Sep 19 07:58:26 nas kernel: ata2.00: status: { DRDY ERR } Sep 19 07:58:26 nas kernel: ata2.00: error: { UNC }
所以我的问题是：是否有一个原因，汽车重新分配失败，并且是可以恢复的。 正如我所说的，数据是由RAID保护的，所以我不担心数据恢复。
smartctl -l selftest /dev/sbd报告第一个坏块的位置。
将坏块HOWTO中描述的过程应用于smartmontools 。
它描述了下面的程序：
smartctl -t short /dev/sdb并在新的坏块的情况下转到1 smartctl -t long /dev/sdb并在新的坏块的情况下转到1