Offline Uncorrectable Sectors

Offline Uncorrectable Sectors is a common disk-related error experienced on Linux machines. Here's a method you can use to understand and fix them.

Fixing Offline Uncorrectable Sectors

Current Pending Sector is the number of locations the disk knows about that needs to be reallocated but haven't reallocated yet.

Since the disk has no source for the data to be reallocated it will remain in this state until you write into that location.

Once that location is written to, the disk will automatically reallocate the area to another place and write the new data in the new place and the current pending sector count will decrease.

You can use diskscan on Linux or HD Tune on Windows to scan the disk for the bad locations and also attempt to "fix" the locations by making the software write into them in order to attempt the reallocation immediately.

This message was generated by the smartd daemon running on:

   host name:  host-example
   DNS domain: example.local

The following warning/error was logged by the smartd daemon:

Device: /dev/sdf [SAT], 1 Offline uncorrectable sectors

Device info:
Micron_1100_MTFDDAK2T0TBN, S/N:17161B3C0923, WWN:5-00a075-11b3c0923, FW:M0MU031, 2.04 TB

For details see host's SYSLOG.

You can also use the smartctl utility for further investigation.
The original message about this issue was sent at Wed May 27 01:46:08 2020 EDT
Another message will be sent in 24 hours if the problem persists.

root@example:~# apt install diskscan

diskscan [options] /dev/sd
Options:
    -v, --verbose        - Increase verbosity, multiple uses for higher levels
    -f, --fix            - Attempt to fix near failures, nothing can be done for unreadable sectors
    -s, --scan <mode>    - Scan in order (seq, random)
    -e, --size <size>    - Scan size (default to 64K, must be multiple of 512)
    -o, --output <file>  - Output file (json)
    -r, --raw-log <file> - Raw log of all scan results (json)
    --force-mounted      - Allow checking a read-only mounted disk
    --force-mounted-rw   - Allow checking a read-write mounted disk

root@example:~# diskscan /dev/sda
diskscan version 0.19

I: Validating path /dev/sda
I: Disk start temperature is 28
I: Opened disk /dev/sda sector size 512 num bytes 5000981077504
I: Scanning disk /dev/sda in 65536 byte steps
I: Scan started at: Thu May 25 11:23:35 2023

Disk scan |                                                                                                        | ETA: 0h00m00s
E: Error when reading at offset 0 size 65536 read -1, errno=0: Success
I: Disk temperature changed from 30 to 31
E: Details: error=need_retry data=none 06/29/00
Disk scan |====                                                                                                    | ETA:10h18m51s