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So when you do a full fsck on a hard drive to find bad blocks, does it ignore or exempt that space on the drive where it puts (reallocates) bad blocks into?

I'm talking about the space implied by the SMART attributes:

196 Reallocated_Event_Count

and

5 Reallocated_Sector_Ct.

The reason I ask is because when I run:

# smartctl -a /dev/sda

I get the following output:

smartctl 5.41 2011-06-09 r3365 [x86_64-linux-3.2.0-40-generic] (local build)

Copyright (C) 2002-11 by Bruce Allen, http://smartmontools.sourceforge.net

=== START OF INFORMATION SECTION ===
Device Model:     ST320LT007-9ZV142
Serial Number:    W0Q7N7DH
LU WWN Device Id: 5 000c50 05dc9bc9e
Firmware Version: 0004LVM1
User Capacity:    320,072,933,376 bytes [320 GB]
Sector Sizes:     512 bytes logical, 4096 bytes physical
Device is:        Not in smartctl database [for details use: -P showall]
ATA Version is:   8
ATA Standard is:  ATA-8-ACS revision 4
Local Time is:    Thu Apr 11 23:02:21 2013 EDT
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:  (0x82) Offline data collection activity
                    was completed without error.
                    Auto Offline Data Collection: Enabled.
Self-test execution status:      (   0) The previous self-test routine completed
                    without error or no self-test has ever 
                    been run.
Total time to complete Offline 
data collection:        (    0) 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:    (   1) minutes.
Extended self-test routine
recommended polling time:    (  63) minutes.
Conveyance self-test routine
recommended polling time:    (   2) minutes.
SCT capabilities:          (0x303b) SCT Status supported.
                    SCT Error Recovery Control supported.
                    SCT Feature Control supported.
                    SCT Data Table supported.

SMART Attributes Data Structure revision number: 10
Vendor Specific SMART Attributes with Thresholds:
ID# ATTRIBUTE_NAME          FLAG     VALUE WORST THRESH TYPE      UPDATED  WHEN_FAILED RAW_VALUE
  1 Raw_Read_Error_Rate     0x000f   114   099   034    Pre-fail  Always       -       70846592
  3 Spin_Up_Time            0x0003   098   098   000    Pre-fail  Always       -       0
  4 Start_Stop_Count        0x0032   099   099   020    Old_age   Always       -       1442
  5 Reallocated_Sector_Ct   0x0033   100   100   036    Pre-fail  Always       -       0
  7 Seek_Error_Rate         0x000f   068   060   030    Pre-fail  Always       -       6535747
  9 Power_On_Hours          0x0032   100   100   000    Old_age   Always       -       258518376513933
 10 Spin_Retry_Count        0x0013   100   100   097    Pre-fail  Always       -       0
 12 Power_Cycle_Count       0x0032   100   100   020    Old_age   Always       -       300
184 End-to-End_Error        0x0032   100   100   099    Old_age   Always       -       0
187 Reported_Uncorrect      0x0032   100   100   000    Old_age   Always       -       0
188 Command_Timeout         0x0032   100   098   000    Old_age   Always       -       152
189 High_Fly_Writes         0x003a   100   100   000    Old_age   Always       -       0
190 Airflow_Temperature_Cel 0x0022   064   053   045    Old_age   Always       -       36 (Min/Max 36/38)
191 G-Sense_Error_Rate      0x0032   100   100   000    Old_age   Always       -       4
192 Power-Off_Retract_Count 0x0032   100   100   000    Old_age   Always       -       13
193 Load_Cycle_Count        0x0032   099   099   000    Old_age   Always       -       2977
194 Temperature_Celsius     0x0022   036   047   000    Old_age   Always       -       36 (0 15 0 0)
195 Hardware_ECC_Recovered  0x001a   057   054   000    Old_age   Always       -       70846592
196 Reallocated_Event_Count 0x000f   100   100   030    Pre-fail  Always       -       356 (31006, 0)
197 Current_Pending_Sector  0x0012   100   100   000    Old_age   Always       -       0
198 Offline_Uncorrectable   0x0010   100   100   000    Old_age   Offline      -       0
199 UDMA_CRC_Error_Count    0x003e   200   200   000    Old_age   Always       -       0
250 Read_Error_Retry_Rate   0x0000   001   001   000    Old_age   Offline      -       18126
251 Unknown_Attribute       0x0000   001   001   000    Old_age   Offline      -       33297
252 Unknown_Attribute       0x0000   001   001   000    Old_age   Offline      -       14334
254 Free_Fall_Sensor        0x0032   100   100   000    Old_age   Always       -       0

SMART Error Log Version: 1
No Errors Logged

SMART Self-test log structure revision number 1
Num  Test_Description    Status                  Remaining  LifeTime(hours)  LBA_of_first_error
# 1  Vendor (0x50)       Completed without error       00%         1         -

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.

The 196 Reallocated_Event_Count attribute raw value worries me, and I'm planning on running fsck on /dev/sda overnight tonight to see if I really do have bad blocks.

Thanks in advance!

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up vote 0 down vote accepted

So when you do a full fsck on a hard drive to find bad blocks, does it ignore or exempt that space on the drive where it puts (reallocates) bad blocks into?

It ignores it because that space is not addressable from outside the drive.

share|improve this answer
    
Thanks for the clarification. I ran badblocks and the Extended SMART Self Test (from gnome-disk-utility) and neither tool found problems/bad sectors/blocks. That leads to one more question, my 5 Reallocated_Sector_Ct attribute is at 0, while my 196 Reallocated_Event_Count is at 356, as shown. How is that possible? If the firmware did find bad blocks/sectors, but wasn't able to reallocate them successfully, badblocks and that Extended SMART Self Test would've found it, right? Sorry, just paranoid that I might have a bad/dying hard disk. –  oaskamay Apr 12 '13 at 17:52
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