Virtual IO client adapter settings for Dynamic Multi-Pathing (DMP) in dual-VIOS configurations


Virtual IO client adapter settings for Dynamic Multi-Pathing (DMP) in dual-VIOS configurations
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Veritas recommends the following Virtual I/O client (VIO client) adapter settings when using Dynamiic Multi-Pathing (DMP) in dual-VIOS configurations:

Set the vscsi_err_recov attribute to fast_fail.

The virtual SCSI (vSCSI) adapter driver uses the vscsi_err_recov attribute, which is similar to the attribute fc_error_recov for physical fibre channel (FC) adapters. When this parameter is set to fast_fail, the VIO client adapter sends a FAST_FAIL datagram to the VIO server so that the I/O fails immediately, rather than being delayed.
Enable the vscsi_path_to attribute.

This attribute allows the virtual client adapter driver to determine the health of the VIO Server and improve path failover processing. The value of this attribute defines the number of seconds that the vSCSI client adapter waits for commands sent to the vSCSI server adapter to be serviced. If that time is exceeded, the vSCSI client adapter fails the outstanding requests. If DMP is present, another path to the disk will be tried to service the requests.

A value of 0 (default) disables this functionality.

To set the VIO client adapter settings

Set the vscsi_err_recov attribute to fast_fail, and the vscsi_path_to attribute to a non-zero number. For example:
```
# chdev -a vscsi_err_recov=fast_fail -a vscsi_path_to=30 -l vscsi0
```

Verify the settings.

# lsattr -El vscsi0
vscsi_err_recov        fast_fail 
vscsi_path_to          30

Repeat step 1 and step 2 for each vSCSI client adapter.

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