This article will explain the boot log error "ata5: COMRESET failed (errno=-16)" on MX series routers.

Below Logs will be observed when router reboot:

Initiating vmhost reboot ...
Initiating vmhost reboot...
warning: Initiating Junos shutdown...  

Booting in blind mode

ata5: COMRESET failed (errno=-16)
ata5: COMRESET failed (errno=-16)
ata5: COMRESET failed (errno=-16)
ata5: COMRESET failed (errno=-16)
ata5: reset failed, giving up
Try `setpci --help' for more information.
Cannot get kernel page_offset_base symbol address

VMHost crash kernel loaded at reserved memory

The 'ata5: COMRESET failed (errno=-16)' error in the logs points to a system failure to reset SATA disk 1. This error is often linked to disk failures or loose connections. The router's failure to reset ATA channel 5 caused a system halt due to missing SATA disks.

Possible Causes:

• File System Corruption: The file system might be corrupted, making the primary disk unreadable or unmountable.
• Hardware Issues: Transient or permanent hard error on primary disk. 
  
  

Recovery:

To resolve the issue, we may need to follow the below workaround during the MW time:

1. If the device boots up again using the secondary disk, please run the command "request vmhost snapshot recovery partition".
   

   > request vmhost snapshot recovery partition
   
   warning: All existing data on the target media will be lost
   Proceed ? [yes,no] (no) yes
   
   Creating snapshot on target disk from current boot disk .
   Primary disk is recovered now. Please issue "request vmhost reboot" to boot from the primary disk.
   Software snapshot done

2. Reboot the affected RE using the command "request vmhost reboot".
   
   
3. If Re still boots from the alternate disk, then please perform CB offline/online 
   

• request vmhost power-off other-routing-engine
• request chassis cb slot offline <>
• request chassis cb slot online <>

If the issue persists, please open a case with JTAC Support.