Iv. netware drivers – Asus P/I-P65UP8/CP6ND User Manual

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ASUS P/I-P65UP8 User’s Manual

IV. NETWARE DRIVERS

. NETW

ARE

(Command Lines)

Enabling this option results in the driver issuing tagged IO requests to the devices
that support tagged queuing. Devices that do not support tagged queuing are not
issued tagged requests. Depending on the drive controller, throughput of the device
is increased by the use of queue tags. However, the optimal number of queue tags is
based on the specific device type.

Using the Depth of Queue Tags Option
Command line option: qdepth=

Valid options:

0-128

Function:

Set the depth of the queue for tagged queuing. This value
designates the depth of the queue per LUN (I_T_L nexus).
That is, this value designates the depth of the queue per
device, or per LUN, if a device has multiple LUNs.

Possible Impact:

Used to optimize the performance of tagged queuing.

This option is valid only when tagged queuing (qtags) is enabled, which it is by
default. Values possible for this parameter range from 0 to 128. 0 is equivalent to
qtags=disable. While the actual depth of the queue depends on the specific drive
controller. For single drives, values of about 10-30 are typically optimal.

Sometimes a greater number is optimal for peripherals such as disk arrays. You
should experiment with various qdepth values to determine the optimal performance
for their particular setup. The optimal qdepth value is based on different aspects of
the system, including but not limited to: the processor, the available memory, the
disk drives, and other peripherals.

NOTE: The driver supports a maximum of 128 qtags per controller at a given
time. The driver may allocate fewer qtags per device if this limit is being reached.

Using the Queue Tag Type Option
Command line option: qtag_type=

simple

Valid options:

simple, ordered

Function:

Specify the type of tagged commands the device is issued.

Possible Impact:

Ordered type is required for certain devices to avoid IO
starvation.

This option is valid only when tagged queuing (qtags) is enabled, which it is by
default. Simple qtags are typically the preferred tag type. It is sometimes necessary
to use ordered tags on certain devices to avoid IO starvation under extremely heavy
IO loads such as a NetWare remirror process.