These issues occur when the guest operating system timeout values are exceeded for attached storage disks. This may be caused by an underlying storage problem or due to brief transient pauses during normal operations (such as path failover). To accommodate transient events, the VMware Tools increases the SCSI disk timeout to 60 seconds for Virtual Infrastructure 3 and 180 seconds for vSphere 4 and higher.

If the default increase is insufficient for a given environment or if an increase is desired and the VMware Tools is not or cannot be installed, the SCSI device timeout within the Linux guest operating system can be increased manually.

Note: Increasing the SCSI Timeout value is to alleviate the issue of slow Failover/Transient storage conditions. It is not designed to mitigate prolonged underlying storage conditions such as APD/PDL. There may be underlying SAN storage problems that require addressing if:

• Increasing the timeout value does not help.
• Increasing the timeout value does help when increased to a very high value, such as in excess of 180 seconds.
  
  Note: If you are using NetApp storage, for more information regarding timeout values, see NetApp Knowledge Base article What are the guest OS tunings needed for a VMware SAN deployment?.
  
  Note: The preceding link was correct as of July 3, 2014. If you find the link is broken, provide feedback and a VMware employee will update the link.
  
  
• The issue occurs outside of path failover events.
  
  For additional information, see Troubleshooting a virtual machine outage across multiple hosts connected to the same array (1003615).

• Inconsistent Linux operating system performance when disks are located on SAN-based datastores.
• The Linux guest operating system may experience intermittent issues when stored on SAN-based datastores.
• During a host storage path failover, a Linux guest operating system reports a system error or file system error, encounters a kernel panic, or becomes unresponsive.

• Check the current timeout for every generic SCSI device in Linux sysfs using the command:
  
  find /sys/class/scsi_generic/*/device/timeout -exec grep -H . '{}' \;
  
  
• The timeout value for an individual disk can be modified using the sysfs interface. For example:
  
  echo 180 > /sys/block/ sdc/device/timeout
  
  Note: This change does not persist across reboots.
  
  
• The VMware Tools installer creates a udev rule at /etc/udev/rules.d/99-vmware-scsi-udev.rules that sets the timeout for each VMware virtual disk device and reloads the udev rules so that it takes effect immediately. This rule is applied during each subsequent startup. For example, this is the udev rule from vSphere 4.x:
  
  # Redhat systems
ACTION=="add", BUS=="scsi", SYSFS{vendor}=="VMware, " , SYSFS{model}=="VMware Virtual S", RUN+="/bin/sh -c 'echo 180 >/sys$DEVPATH/device/timeout'"

# Debian systems
ACTION=="add", SUBSYSTEMS=="scsi", ATTRS{vendor}=="VMware " , ATTRS{model}=="Virtual disk ", RUN+="/bin/sh -c 'echo 180 >/sys$DEVPATH/device/timeout'"

# SuSE / Ubuntu systems
ACTION=="add", SUBSYSTEMS=="scsi", ATTRS{vendor}=="VMware, " , ATTRS{model}=="VMware Virtual S", RUN+="/bin/sh -c 'echo 180 >/sys$DEVPATH/device/timeout'"