HP 3PAR OS 3.1.3 CLI Administrator's Manual

• When upgrading the host hardware to a newer generation that offers more CPU power and/or
memory (for example, from G6 to Gen8 Proliant blades), generating more IOPS and
bandwidth, or when hardware details change in a virtualized server environment.
• When deploying a new generation of an operating system on the host like moving from
Windows Server 2003 to the Windows Server 2008 or Windows Server 2012 version, or
when moving from a 32-bit to 64-bit environment.
• When deploying a new brand of generation of FC or iSCSI HBAs on the host that have specific
queue depth requirements.
NOTE: Queue depth is the average number of I/O jobs, either processing or waiting to be
processed, within a polling interval. The queue depth is a non-negative integer number.
• When upgrading the end-to-end SAN pathing from 4 Gb/sec to 8 Gb/sec.
In general, HP recommends review of the system I/O capability and adjustment of the QoS rules
in use whenever a change was made to one part of the entire chain from the host to the HP 3PAR
OS.
Handling Tier-1 Applications
The HP 3PAR StoreServ storage systems are Tier-1 arrays that can handle multiple mission-critical
workloads concurrently, as opposed to workloads of medium importance and performance
requirements. Tier-1 applications should be given all resources they need during runtime, given
their vital business impact.
HP recommends that a QoS rule be defined with sensible limits for IOPS and bandwidth on all
VVsets that have a known I/O profile. The System rule should be defined to control all volumes
created on the system that do not have an explicitly defined QoS rule.
If you don’t set a QoS rule, and the all_others rule is active, mission-critical applications will
be subject to the all_others rule. To prevent the System rule from controlling the Tier-1
applications, define a QoS rule with very high values for IOPS and bandwidth. This way, the
mission-critical workload will be able to consume the I/O resources they need to perform optimally.
Implementing the System Rule
Workloads without a QoS rule consume I/O resources in an uncontrolled manner and may starve
those that are subject to a QoS rule. To ensure an acceptable level of performance across all
applications on a storage system if QoS is used, all volumes must be part of a QoS rule with
meaningful limits reflecting the application’s I/O requirements. The System QoS rule should be
enabled and a value specified for its maximum IOPS and bandwidth to control the I/O traffic from
VVs and VVsets not subject to a specific QoS rule. This prevents any new volumes added to the
HP 3PAR StoreServ or existing ones that are not subject to a QoS rule from negatively affecting
the entire system overconsuming IOPS or bandwidth.
The default minimum allowed values for the System rule are 1000 for the I/O Limit and 100,000
KB/sec for the bandwidth limit. Be sure to change these to acceptable values if the defaults are
deemed too small.
Overprovisioning the System
HP 3PAR Priority Optimization allows over-provisioning when creating QoS rules: rules whose
combined value for IOPS or bandwidth can exceed the I/O capacity of an HP 3PAR StoreServ.
This is an established practice if the workloads are sufficiently orthogonal in their I/O usage.
For example, a database used only during the day time and a backup application running only
during the night can each be given the entire I/O capacity of the system in their respective QoS
rules. When overprovisioning concurrent workloads, QoS prevents a single application or customer
from monopolizing the system.
156 HP Priority Optimization