6.7

VMware NMP Flow of I/O
When a virtual machine issues an I/O request to a storage device managed by the NMP, the following
process takes place.
1 The NMP calls the PSP assigned to this storage device.
2 The PSP selects an appropriate physical path on which to issue the I/O.
3 The NMP issues the I/O request on the path selected by the PSP.
4 If the I/O operation is successful, the NMP reports its completion.
5 If the I/O operation reports an error, the NMP calls the appropriate SATP.
6 The SATP interprets the I/O command errors and, when appropriate, activates the inactive paths.
7 The PSP is called to select a new path on which to issue the I/O.
Display Multipathing Modules
Use the esxcli command to list all multipathing modules loaded into the system. Multipathing modules
manage physical paths that connect your host with storage. The modules include VMware native NMP
and HPP, and any third-party MPPs.
Prerequisites
Install vCLI or deploy the vSphere Management Assistant (vMA) virtual machine. See Getting Started with
vSphere Command-Line Interfaces. For troubleshooting, run esxcli commands in the ESXi Shell.
Procedure
u
To list multipathing modules, run the following command:
esxcli storage core plugin list --plugin-class=MP
This command typically shows the NMP and, if loaded, the HPP and the MASK_PATH module. If any
third-party MPPs have been loaded, they are listed as well.
Plugin name Plugin class
----------- ------------
NMP MP
For more information about the command, see the vSphere Command-Line Interface Concepts and
Examples and vSphere Command-Line Interface Reference documentation.
Display NMP Storage Devices
Use the esxcli command to list all storage devices controlled by the VMware NMP and display SATP
and PSP information associated with each device.
vSphere Storage
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