HP QR516B manual LUN Set to Round Robin

Figure 10 LUN Set to Round Robin

Managing a round robin I/O path policy scheme through the VI/vSphere client GUI for a large network can be cumbersome and challenging to maintain because the policy must be specified for each LUN individually and updated whenever new devices are added. Alternatively, VMware provides a mechanism whereby the server administrator can use esxcli, vCLI, or vSphere Management Assistant (vMA) commands to manage I/O path policy for storage devices on a per-host basis using parameters defined within a set of native ESX/ESXi storage plugins.

The VMware native multipathing has two important plugins: a Storage Array Type Plugin (SATP) that handles path failover and monitors path health, and a path-selection plugin (PSP) that chooses the best path and routes I/O requests for a specific logical device (PSP defines the path policy).

The correct ESX/ESXi host Storage Array Type Plugin (SATP) to be used is related to the HP 3PAR array host persona in use. When HP 3PAR host persona 6/Generic-legacyis the host persona in use with an ESX/ESXi host, the SATP VMW_SATP_DEFAULT_AA should be used. When HP 3PAR host persona 11/VMware is the host persona in use with an ESX/ESXi host, the SATP VMW_SATP_ALUA should be used.

For ESX/ESXi 4.0 versions (4.0 GA through all 4.0 updates), the default SATP rules must be edited in order to automatically achieve a round robin I/O path policy for storage devices.

As of ESX/ESXi 4.1, additional custom SATP rules can be created that target SATP/PSP to specific vendors while leaving the default SATP rules unmodified. The custom SATP can be used to automatically achieve a round robin I/O path policy for storage devices.

Configuring ESX/ESXi Multipathing for Round Robin via SATP PSP

CAUTION: VMware specifically warns not to directly edit the esx.conf file.

40 Configuring the Host for a Fibre Channel Connection