Setup if your deployment includes a shared switch

Requirement to limit the target queue length limitation

If your deployment includes a shared switch, you need to plan for and configure the gFilers to limit the number of commands (read and write requests) that the storage subsystem port must handle as a result of gFilers and non-gFiler hosts accessing the port through the switch; that is, you need to plan for limiting the target queue length. When multiple initiators are accessing a target port on the storage subsystem, you do not want the outstanding commands in the queue buffer, from all initiators together, to exceed 256. Otherwise, the performance of gFiler and non-gFiler hosts can suffer.

On gFilers, you use the disk.target_port.cmd_queue_depth option to set the number of commands that the gFiler can send to the target port on the data subsystem. You do not set this option until after you set up and install Data ONTAP on your gFiler.

Non-gFiler hosts also provide a means for limiting the target queue length. See the documentation for the host for information about limiting target queue length.

Note
Target queue length might also be referred to as Q-Depth or Max Throttle.

Guidelines for determining the appropriate target queue length

You need to consider the impact of all the initiators on the port when you are planning the configuration for a specific gFiler or a specific non-gFiler host. If your deployment includes more than one initiator, you need to configure each initiator so that the total commands by all initiators does not exceed 256. The default for target queue depth value is 256.

Some guidelines for determining the appropriate target queue length are as follows:

0 (zero) means no limit on the outstanding commands. Therefore, do not configure a value of 0.
You could divide 256 by the number of gFiler and non-gFiler hosts that will be acting as initiators on the target port on the storage subsystem, configuring each gFiler and non-gFiler host with the value that resulted.
You could consider the volume of commands that specific initiators would be likely to send to the target port. You could then configure higher values for initiators likely to send a greater number of requests and a lower value for initiators likely to send a lesser number of requests.

Configure non-gFiler hosts according to the guidelines provided for those hosts.

Setting the target queue depth length

To set the disk.target_port.cmd_queue_depth option, complete the following step.

Step	Action
1	Enter the following command at the Data ONTAP command line: `disk.target_port.cmd_queue_depth <`value`>` Do not use a value of 0 (zero) because it means no limit on the outstanding commands.