iSCSI LUN appears online but is unavailable for IO

Applies To

• Gen1 / Gen2 Hybrid and All Flash Series
• Effected Software Versions : 1.8.x , 2.1.0

Issue

No faults present in NGX GUI.
iSCSI initiators and paths are good.
Host unable to access the LUN.

From the host logs there are continuous failed attempts to access the LUN, for example from an ESX host:

WARNING: NMP: nmp_DeviceStartLoop:729: NMP Device "naa.589c008063872cb1d3900ee2d7d0108c" is blocked. Not starting I/O from device.
NMP: nmp_DeviceRetryCommand:133: Device "naa.589c008063872cb1d3900ee2d7d0108c": awaiting fast path state update for failover with I/O blocked. No prior reservation exists on the device.

Cause

During an controller reboot a rare trespass race condition can happen in the mapped LUNs. The result is that the LUN is left in a ready state until peer controller up and announce active paths. Only iSCSI LUNs effected from this problem, Fibre Channel LUNs are not.

Resolution

A fix for this issue is expected to be available in the next major software release for Gen2 series (2.2.0).
For Gen1 series its expected to fix with 1.8.6 release.

Additional Information

N/A