How to properly tune an ESXi server that is connected to a Symmetrix

ESXi 5.x -> ESXi 6.x

How to properly tune an ESXi server that is connected to a Symmetrix.

Degraded performance is seen on new or existing ESXi servers zoned to Symmetrix storage arrays.
Degraded performance on an ESXi server attached to a DMX, VMAX, or VMAX3 array

A tunable setting for VMware's Native Multipathing (NMP) Round Robin (RR) policy is incorrectly set or is still set to the default value of 1000.

The NMP RR policy I/O operations limit should be set to a value of "1" when attached to a Symmetrix.

For ESX/ESXi 4.x:

• To check the I/O operations limit: esxcli nmp roundrobin getconfig --device=<device NAA>
• To set the I/O operations limit: esxcli nmp roundrobin setconfig --device=<device NAA> --iops 1 --type iops

For ESXi 5.x:

• To check the I/O operation limit: esxcli storage nmp psp roundrobin deviceconfig get --device=<device NAA>
• To set the I/O operations limit: esxcli storage nmp psp roundrobin deviceconfig set --device=<device NAA> --iops=1 --type iops

Prior to VMware ESXi 5.1 the default path selection policy (PSP) for the Symmetrix array type plug-in (SATP) was fixed. The PSP for Symmetrix SATP should be changed to a Round Robin policy (the default policy in ESXi 5.1). When this change is applied, NMP channels I/O in a Round Robin fashion across all active paths.

However, the frequency of the path switching is controlled by a parameter called "i/o operation limit" and by default is set to 1000. This is incorrect when zoned to a Symmetrix only.

Before engaging the performance teams at Dell Technologies, the following article should be reviewed and applied. This tunable affects I/O performance on all ESXi servers attached to Symmetrix storage arrays.