HP 3PAR OS 3.1.3 CLI Administrator's Manual

For another example, a system capable of 50 k IOPS could have 10 customers, each limited to
10 k IOPS. The system is over-provisioned for IOPS, but no single customer can monopolize the
system. Continuous monitoring of system performance by HP 3PAR System Reporter is mandatory
to ensure that every application and customer performs well without reaching their I/O limits.
QoS Influence on the Host Side
The QoS rules in HP 3PAR Priority Optimization specify the relative importance of the I/O of each
workload on the storage system. When the IOPS or bandwidth demand of an application reaches
the implemented QoS limits, the performance of the application on the host will no longer grow.
Lowering the QoS cap will result in higher I/O response times and reduced throughput on the host,
and eventually queue-full errors are returned by the array to the host.
NOTE: Response time is the average measured time that it takes the array to process an I/O
request. On HP 3PAR StoreServ Storage systems, response time may be reported as “service time.”
Response time is measured in milliseconds.
On the other hand, a lowered QoS cap for one workload will free I/O resources on the host,
which in turn may reduce memory and CPU cycle consumption to the benefit of other workloads.
HP 3PAR Priority Optimization can control host-side resources, obviating the need to define QoS
and metrics in a workload manager tool on the host. However, host-side and storage system QoS
rules can be combined for tighter control, or when memory and CPU cycle consumption management
is required on the host.
Maximum Number of QoS Rules per VV
A given VV can be part of a large number of VVsets. HP does not recommend application of
multiple QoS rules to the same VV. For this reason, QoS rules can be defined on a maximum of
eight VVsets that contain a particular VV. The lowest value for IOPS and bandwidth, for a VVset
that hosts a VV, imposes its limits on the I/O traffic to and from the VV.
QoS on a Subset of VVset Volumes
By default, a QoS rule on a VVset governs all volumes in the set; but only a subset of the volumes
in the VVset might need a QoS rule. In this situation, create a second VVset that contains only the
volumes that need a QoS rule, and then define the rule. The volumes in the second VVset do not
need to be exported for the QoS rule to take action.
If the System rule is defined, it takes action on all VVsets for which a QoS rule has not been
defined. If at least one volume of the VVset has a QoS rule defined in another VVset, the named
QoS rule takes precedence over the System rule, even if the named QoS rule has a lower value
for IOPS or bandwidth.
Application Interoperability
HP 3PAR Priority Optimization sets and manages QoS rules defined on I/O traffic. Software
products for HP 3PAR StoreServ storage systems, such as Dynamic Optimization (DO), Adaptive
Optimization (AO), Virtual and Physical Copy, HP 3PAR System Reporter, the Thin Provisioning
Suite, and the Recovery Manager packages work on data in the backend. This means they are all
compatible and operate transparently to HP 3PAR Priority Optimization.
Databases
All database software vendors recommend that you separate data files, index files, and transactional
and archive logs on separate volumes. The write capability and location of the online transaction
logs are most important as the entire performance of the database depends on the writes to these
logs. For this reason a QoS rule on the volumes containing the online transaction logs should be
carefully dimensioned to not inhibit the performance of the database. QoS rules on the I/O
performance of the database volumes will take care of runaway queries that consume IOPS and
Using HP 3PAR Priority Optimization 157