HP StorageWorks Enterprise File Services WAN Accelerator 3.0.4 deployment guide (AG421-96001, March 2007)

104 10 - QUALITY OF SERVICE
HP EFS WAN Accelerators use Hierarchical Fair Service Curve (HFSC) QoS
operations to simultaneously control bandwidth and latency for each QoS class. For
each class, you can set a:
 Priority level. There are five QoS class priorities, as described in “About QoS
Class Priorities” on page 104.
 Minimum guaranteed bandwidth level, which specifies the minimum amount of
bandwidth a QoS class is guaranteed to receive when there is bandwidth
contention. If unused bandwidth is available, a QoS class receives more than its
minimum guaranteed bandwidth level. The percentage of excess bandwidth each
QoS class receives is relative to the percentage of minimum guaranteed
bandwidth it has been allocated.
The total minimum guaranteed bandwidth level of all QoS classes must be less
than or equal to 100%.
 Maximum bandwidth level, which specifies the maximum amount of bandwidth a
QoS class is allowed to use, regardless of the available excess bandwidth.
 Connection limit, which specifies a maximum number of connections the
specified QoS class will optimize. Connections over this limit are passed-through.
Connection limit can only be set in the CLI. For information, see the HP
StorageWorks Enterprise File Services WAN Accelerator Command-Line
Interface Reference Manual.
Once you have defined a QoS class, you can create a QoS rule to apply to it. QoS rules
define source subnet or port, destination subnet or port, protocol, traffic type, and
virtual local area network (VLAN) and Differentiated Service Code Point (DSCP)
filters for a QoS class.
About QoS
Class Priorities
There are five QoS priorities for HP EFS WAN Accelerators. You assign a class
priority when you create a QoS class. Once you have created a QoS class, you can
modify its class priority. In descending order, class priorities are:
 Realtime.
 Interactive.
 Business Critical.
 Normal.
 Low Priority.
Priority levels are minimum priority guarantees. If higher priority service is available,
a QoS class will receive it even if the class has been assigned a lower priority level.
For example, if a QoS class is assigned the priority level Low Priority, and QoS classes
that are assigned higher priority levels are not active, the low priority QoS class adjusts
to the highest possible priority for the current traffic patterns.
Maximum
Allowable QoS
Classes and
Rules
The number of QoS classes and rules you can create on an HP EFS WAN Accelerator
depends on the appliance model number, as described in the following table.