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Write-cache disabled on storage array causing performance issues or failures (1002282)

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  • Poor disk I/O performance to the storage array, causing very slow or the failure of:
    • Template deployments
    • Cold migrations
    • vMotion
    • VMware Consolidated Backup

  • In cases where the ESX/ESXi environment is large, write caching suddenly becoming disabled can result in a performance degradation that makes communication to the LUNs impossible. If this occurs, you may experience these symptoms:
    • Virtual machines fail or stop responding.
    • High device latency (DAVG) values seen via esxtop
    • VMFS datastores go off-line with the following error message in the logs:

      Lost heartbeat


Write caching must always be enabled.
On many arrays, write caching is automatically turned off when:
  • The battery backup is disconnected
  • The battery backup fails
  • One of the redundant power supplies disconnects or fails.

To ensure that write caching does not become disabled, VMware recommends that you have a battery backup connected.

Note: For more information on enabling write-cache, contact your storage hardware vendor.



This Article Replaces


Update History

10/11/2014 - Added VMware ESXi 5.0.x, ESXi 5.1.x and ESXi 5.5.x under Product Version.

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  • 13 Ratings