[smartmontools-support] Differences in test report results: xselftest vs selftest

[Daniel Fishman]

Hello,

When smartctl displays results of hdd's selftest, contents of the report
differ, depending on whether you ask for an extended or a regular self test.
For extended test (smartctl -l xselftest /dev/sdc), it says:

---------------------------------------------------------------
SMART Extended Self-test Log Version: 1 (1 sectors)
Num  Test_Description    Status                  Remaining  LifeTime(hours)  LBA_of_first_error
# 1  Extended offline    Completed: read failure       90%      4899         281474968262399
# 2  Extended offline    Completed: read failure       90%      4897         281474968262399
# 3  Extended offline    Completed: read failure       90%      4897         281474968262399
# 4  Extended offline    Completed: read failure       90%      4897         281474968262399
# 5  Extended offline    Completed: read failure       90%      4864         7336633448
# 6  Extended offline    Completed: read failure       90%      4864         7336633448
# 7  Extended offline    Completed: read failure       90%      4863         7336633448
# 8  Extended offline    Completed: read failure       90%      4863         7336633448

---------------------------------------------------------------

For regular test (smartctl -l selftest /dev/sdc), it says:
---------------------------------------------------------------
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%      4899         4286519039
# 2  Extended offline    Completed: read failure       90%      4897         4286519039
# 3  Extended offline    Completed: read failure       90%      4897         4286519039
# 4  Extended offline    Completed: read failure       90%      4897         4286519039
# 5  Extended offline    Completed: read failure       90%      4864         3041666152
# 6  Extended offline    Completed: read failure       90%      4864         3041666152
# 7  Extended offline    Completed: read failure       90%      4863         3041666152
# 8  Extended offline    Completed: read failure       90%      4863         3041666152
---------------------------------------------------------------

Also, 'fdisk -lu /dev/sdc' says:

---------------------------------------------------------------
Disk /dev/sdc: 3.64 TiB, 4000752599040 bytes, 7813969920 sectors
Disk model: My Passport 260D
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: gpt
Disk identifier: 8A1DDBC3-1CA2-40EB-9245-2FB3B4DAC117

Device     Start        End    Sectors  Size Type
/dev/sdc1   2048 7813967871 7813965824  3.6T Linux filesystem
---------------------------------------------------------------


It is clear that both extended & regular reports show info about the same
set of executed tests, but why they report different bad sectors? Moreover,
results from extended test don't make sense - the hdd has only 7813969920
sectors, it cannot have sector 281474968262399.

Also, I want to fix bad sectors as explained in the wiki
(https://www.smartmontools.org/wiki/BadBlockHowto),
and while the wiki uses results of a regular test, I have a bit of
a problem with following the wiki (which is the reason why I started to look
at various smartctl's reports and eventually noticed the difference above):
since smartctl consistently reports the same bad sector, I expected that
an attempt to read it with hdparm (hdparm --read-sector 4286519039 /dev/sdc)
should fail, or at least produce some error message - but hdparm reads
this sector successfully.

 From all this it seems as though *both* reports are incorrect: one complains
about a non-existent sector, another complains about a good readable sector.

How can I interpret those reports and use their results to fix the
reported problem?

Note: I use smartctl 7.4