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The importance of storage QoS with flash


Ivan.jpegBy Ivan Iannaccone, HP 3PAR StoreServ Product Management   @IvanIannaccone


I love to talk to customers about Priority Optimization. It’s a feature of HP 3PAR StoreServ that allows storage QoS to give you the ability to provision performance as you provision capacity, assuring that your important workloads get expected performance. The Evaluator Group recently completed an evaluation paper that shows how Priority Optimization can be used in a mission-critical all-flash environment. So this 3PAR Thursday, I’m taking this ideal opportunity to talk a bit more about storage QoS and its importance in all-flash deployments.


Powerful storage QoS requires a powerful architecture

QoS techniques and concepts have been widely available in the networking stack for many years. There have been attempts to port some of these controls to the storage block layer. But these have been bolt-on approaches on storage architectures that where never built for multi-tenancy, so they also come with limited controls and many caveats.


HP 3PAR Priority Optimization relies on HP 3PAR Mesh/Active Architecture and its software virtualization layers. It also leverages the hardware mixed workload engine that is used to separate control data versus the actual data. This assures physical resources (like cache pages) are only assigned when the I/O is supposed to be served according to a given QoS rule. Some competitive approaches assign the hardware resource—and only then wait to process the I/O (that is, apply the QoS rule). This results in starvation of precious system resources from higher priority workloads.


Priority Optimization use cases

Priority Optimization enables a wide range of use cases via its min/max IOPs/TPUT setting and latency goals:

  • Protect important mission-critical apps on a shared infrastructure via latency goals
  • Craft Gold/Silver/Bronze SLAs for multiple tenants
  • Limit rouge workloads or noisy neighbors via max caps limits
  • Define QoS rules in a secure multi-tenant environment on multiple Virtual Private Arrays (VPAs) using virtual domains
  • Satisfy bursts of I/O while maintaining predictable performances via latency goals
  • Limit the amount of system bandwidth used by backup application
  • Back-charge tenants based on performance SLAs

Great expectations

Flash enables massive consolidation at a much lower latency than what can be delivered by spinning media alone. This translates to an improved performance experience for tenants and workloads and creates new expectations.


If you are used to 5ms and 6.000 IOPS, you may now get up to 10.000 (or more) IOPS at 1ms (or less) latency, making this new experience your baseline. Priority Optimization enables you to set and meet these new expectations. As you create and export volume, max limits allow you to determine exactly how much IOPS/BW to provision, as opposed to just giving all the available system performance to any given volume.

As volumes are deployed, you can also protect them from noisy neighbors or day-to-day tasks that consume system resources—so you can meet expectations.


A great example used in Evaluator Group paper is around how Priority Optimization QoS rules help protect production apps in a 24x7 production cloud environment by limiting the amount of system resources that the backup application can use. This is an interesting consideration for deployments when you don’t have or cannot afford to have a backup window during non-production hours.



Read the Evaluator Group paper
Maintaining Application Performance with All Flash Arrays and Storage QoS



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