A virtual machine running on an ESX/ESXi host may report issues that prevent it to function and become unresponsive. This may occur due to configuration issues in the virtual hardware of the virtual machine. This article describes some common virtual machine configuration issues which can lead to a virtual machine becoming unresponsive. This is in no way an exhaustive list of issues that may affect your virtual machine, but it does provide a useful starting point.

For more general troubleshooting of unresponsive virtual machines on ESX/ESXi, see Troubleshooting a virtual machine that has stopped responding (1007819).

• Virtual machines can be configured with limits and shares for common resources such as CPU and memory. If these limits are set aggressively low, a virtual machine may be starved for those resources and be unable to perform meaningful work. For more information, see the Resource Management Guide for your version of ESX/ESXi.
  
  
• Virtual machines can share access to physical CD-ROM devices on the host server. If this device is unavailable or attempts to access it result in read errors (such as from a scratch disk, or a slow connection to a remote ISO), an accessing virtual machine may be blocked while waiting for a response from the device.
  
  For more information on specific examples, see:
  
  
  • Troubleshooting a virtual machine that stops responding or fails when the CD-ROM entry is ATAPI (1005734)
  • Linux virtual machine continuously reports errors related to the CD-ROM drive (1007840)
  • The guest operating system is extremely slow or does not boot when connected to the host CD/DVD drive (2000382)
  
  
• A virtual machine is expected to become stunned during some checkpointing operations, such as during a vMotion or Snapshot operation. Determine whether the issue correlates to a task or other operation performed on the virtual machine. For more information, see Virtual machine in a DRS cluster fails during VCB backup (1002025) and A snapshot removal can stop a virtual machine for long time (1002836).
  
  
• During startup, a virtual machine may pause at 95% with a question that must be answered prior to startup completing.
  For more information, see Answering a virtual machine related question from the command line (1026835).
  
  
  Note:
  
  
• For VDI products, there may be very high Stun if digest disks is part of the backup plan for View desktops. The reason behind that is that the digest disks are built at runtime if they do not already exist. Anything that is auto-generated should not be a part of your backups.
• Our recommendation is to alter backup plan to only backup the required files for each desktop.