ESXi host returns "Input / Output error" while opening the log files in /var/log

Products

• VMware vSphere ESXi

Issue/Introduction

ESXi host returns "Input / Output error" while opening the log files in /var/log. 

• Scratch partition is configured
• The ESXi host is still actively hosting the VMs. 
• Connected to the vCenter

Since the logs from the disk location could not be accessed, refer to the kernel messages in the memory by running "dmesg"

It shows SCSI command failure warnings related to the disk repeatedly.

2025-07-10T04:22:44.249Z cpu1:2012367)ScsiDeviceIO: 4167: Cmd(0x45b9e0763f48) 0x2a, CmdSN 0x5ce066b from world 2135457 to dev "naa.<device_id>" failed H:0x1 D:0x0 P:0x0   
2025-07-10T04:22:44.249Z cpu1:2012367)ScsiDeviceIO: 4167: Cmd(0x45b9e38f88c8) 0x2a, CmdSN 0x5ce066c from world 2135457 to dev "naa.<device_id>" failed H:0x1 D:0x0 P:0x0   

Note: Interpreting SCSI sense codes in VMware ESXi

The naa.<device_id> matches the LUN that backs the scratch partition. 

Such situations may lead to : 

• boot failures depending upon the disk failure. 
• host not responding (hostd becomes unstable)

Cause

This issue occurs as the disk that is backing the scratch partition is faulty.

 

Resolution

Evacuate the VMs and place the host in maintenance mode.

Involve the hardware vendor to investigate the disk failure.

Additional Information

Refer to Identifying disks when working with VMware ESXi to identify the disk.