The smart attribute raw_read_error_rate for mw1230's sdb went up during the monthly mdadm check, filing here for reference and to understand what we can do about it. Note the attribute can go up but also down, suggesting it is considered over a window of time.
root@mw1230:~# smartctl --health --attributes /dev/sda smartctl 6.6 2016-05-31 r4324 [x86_64-linux-4.9.0-6-amd64] (local build) Copyright (C) 2002-16, Bruce Allen, Christian Franke, www.smartmontools.org === START OF READ SMART DATA SECTION === SMART overall-health self-assessment test result: FAILED! Drive failure expected in less than 24 hours. SAVE ALL DATA. See vendor-specific Attribute list for failed Attributes. 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 018 001 051 Pre-fail Always FAILING_NOW 13218 3 Spin_Up_Time 0x0027 145 145 021 Pre-fail Always - 3733 4 Start_Stop_Count 0x0032 100 100 000 Old_age Always - 28 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 067 067 000 Old_age Always - 24361 10 Spin_Retry_Count 0x0032 100 253 000 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 - 22 192 Power-Off_Retract_Count 0x0032 200 200 000 Old_age Always - 18 193 Load_Cycle_Count 0x0032 200 200 000 Old_age Always - 46 194 Temperature_Celsius 0x0022 116 107 000 Old_age Always - 27 (Min/Max 0/36) 196 Reallocated_Event_Count 0x0032 200 200 000 Old_age Always - 0 197 Current_Pending_Sector 0x0032 200 200 000 Old_age Always - 6 198 Offline_Uncorrectable 0x0030 200 200 000 Old_age Offline - 1 199 UDMA_CRC_Error_Count 0x0032 200 200 000 Old_age Always - 0 200 Multi_Zone_Error_Rate 0x0008 142 142 000 Old_age Offline - 11677
