Troubleshooting Tip: Explaining the error 'previous I/O error to superblock detected'

The following error may be observed in the console or events:

previous I/O error to superblock detected

previous I/O error to superblock detected

previous I/O error to superblock detected

This error means that the system was unable to read/write to some cells on the disk. It might be caused by firmware (wrong/incomplete write cycle terminated by the power cycle or so) or by hardware failure in some parts/tracks/cells of the disk.

It is suggested to perform a cold reboot of the device and observe if the errors persist. Otherwise, it is possible to perform the following steps:

1. Take a configuration backup of the device: Configuration backups and reset.
   
   
2. Format the BIOS in the device and rewrite the same firmware again: Technical Tip: Formatting and loading FortiGate firmware image using TFTP.
   
   
3. Check crash logs on the FortiGate and confirm if the following logs are seen continuously: 
   
   

diagnose debug crashlog read

EXT2-fs (sda2): previous I/O error to superblock detected
EXT2-fs (sda2): previous I/O error to superblock detected

4. Check the system event logs, and the following logs may appear:

"date=2025-04-14 time=14:17:56 id=759817687336199053 itime="2026-01-22 14:24:12" euid=3 epid=3 dsteuid=3 dstepid=3 logver=704076595 logid=0100020010 type="event" subtype="system" level="critical" msg="EXT2-fs (sda1): previous I/O error to superblock detected" logdesc="Kernel error" eventtime=1769088757646884917 tz="+0100" devid="FG4H0XXXXXX" vd="root" dtime="2025-04-14 12:14:46" itime_t=1768767552 devname="TEST""

5. Run a hardware inspection test for the disk and check the results: 

diagnose hardware test disk file-data
diagnose hardware test disk file-data2
diagnose hardware test disk hdd-block-wrv
diagnose hardware test disk file-varlog

6. Restore the configuration and observe the unit: Configuration backups and reset.

If an error similar to 'previous I/O error to superblock detected' is still received, move the ticket to the RMA Team, as the device is faulty.

Note: Upon the first reboot attempt after this error occurs, a boot failure may occur at the BIOS level. In this situation, the device will boot normally after a power cycle (removing and reapplying power).

Related articles:

• Troubleshooting Tip: Log disk failure Imminent, prioritize data backup and disk replacement 
• Technical Tip: RMA - HQIP test (with hardware test image) 
• Technical Tip: RMA: HQIP test (with built-in FortiOS diagnostic commands) 
  
• Troubleshooting Tip: 'ata6: COMRESET failed (errno=-32)' error in console after factory reset