NMP stands for Native Multipathing.

The NMP is an extensible module that manages subplugins.

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– Manages physical path claiming and unclaiming.
– Registers and de-registers logical devices.
– Associates physical paths with logical devices.
– Processes I/O requests to logical devices:
– Selects an optimal physical path for the request (load balance)
– Performs actions necessary to handle failures and request retries.
– Supports management tasks such as abort or reset of logical devices.

NMP warnings/errors are reported in ESXi logs:

2015-02-14T20:37:58.770Z esx.vmware.com vmkwarning: cpu26:4316)WARNING: NMP: nmp_DeviceStartLoop:722:NMP Device "naa.60a9800041764a4138244378686b4179" is blocked. Not starting I/O from device.

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The NMP_ dashboard comes in to help you visualize those events:

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