vSphere 5.1 Storage Enhancements – Part 4: All Paths Down (APD)

All Paths Down (APD) is a situation which occurs when a storage device is removed from the ESXi host in an uncontrolled manner, either due to administrative error or device failure. Over the previous number of vSphere releases, VMware has made significant improvements to handling the APD, the All Paths Down, condition. This is a difficult condition to manage since we don’t know if the device is gone forever or if it might come back, i.e. is it a permanent device loss or is it a transient condition.

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