smartd: 7 Seek_Error_Rate changed.

В логе появляются вот такие записи:
Apr 11 04:15:41 Device: /dev/sda, SMART Prefailure Attribute: 7 Seek_Error_Rate changed from 200 to 100
Apr 11 10:45:41 Device: /dev/sda, SMART Prefailure Attribute: 7 Seek_Error_Rate changed from 100 to 200
Apr 11 11:15:41 Device: /dev/sda, SMART Prefailure Attribute: 7 Seek_Error_Rate changed from 200 to 100
Apr 11 13:45:41 Device: /dev/sda, SMART Prefailure Attribute: 7 Seek_Error_Rate changed from 100 to 200

=== START OF INFORMATION SECTION ===
Model Family: Western Digital Caviar RE Serial ATA family
Device Model: WDC WD1600YS-01SHB1
===
ID# ATTRIBUTE_NAME FLAG VALUE WORST THRESH TYPE UPDATED WHEN_FAILED RAW_VALUE
1 Raw_Read_Error_Rate 0x000f 200 200 051 Pre-fail Always - 0
3 Spin_Up_Time 0x0003 186 183 021 Pre-fail Always - 3658
4 Start_Stop_Count 0x0032 100 100 000 Old_age Always - 22
5 Reallocated_Sector_Ct 0x0033 200 200 140 Pre-fail Always - 0
7 Seek_Error_Rate 0x000f 200 200 051 Pre-fail Always - 0
9 Power_On_Hours 0x0032 076 076 000 Old_age Always - 17813
10 Spin_Retry_Count 0x0013 100 253 051 Pre-fail Always - 0
11 Calibration_Retry_Count 0x0013 100 253 051 Pre-fail Always - 0
12 Power_Cycle_Count 0x0032 100 100 000 Old_age Always - 21
194 Temperature_Celsius 0x0022 108 097 000 Old_age Always - 39
196 Reallocated_Event_Count 0x0032 200 200 000 Old_age Always - 0
197 Current_Pending_Sector 0x0012 200 200 000 Old_age Always - 0
198 Offline_Uncorrectable 0x0010 200 200 000 Old_age Offline - 0
199 UDMA_CRC_Error_Count 0x003e 200 200 000 Old_age Always - 0
200 Multi_Zone_Error_Rate 0x0009 200 200 051 Pre-fail Offline - 0
===
Что бы это значило?