QoS is a means to ensure specific performance levels for applications and workloads. There are two ways to accomplish this:
1. Ability to set limitations to avoid unwanted behavior from non-critical clients/hosts.
2. Ability to set guarantees to ensure service levels for mission-critical clients/hosts.

Pivot3 Acuity supports the second method through pre-defined performance policies per volume. These policies can be changed manually on-the-fly or automatically by configuring and assigning schedules.

Available QoS Policies on All-Flash Acuity X5 models:
Policy 1 – Mission Critical – 125,000IOPs 1,000MB/s 1ms
Policy 2 – Business Critical – 75,000IOPs 500MB/s 3ms
Policy 3 – Business Critical – 50,000IOPs 250MB/s 10ms
Policy 4 – Non-Critical – 25,000IOPs 100MB/s 20ms
Policy 5 – Non-Critical – 10,000IOPs 50MB/s 40ms

Available QoS Policies on Hybrid Acuity X5 models:
Policy 1 – Mission Critical – 100,000IOPs 750MB/s 5ms
Policy 2 – Business Critical – 50,000IOPs 375MB/s 10ms
Policy 3 – Business Critical – 20,000IOPs 150MB/s 25ms
Policy 4 – Non-Critical – 10,000IOPs 75MB/s 50ms
Policy 5 – Non-Critical – 2,000IOPs 37.5MB/s 100ms

The pre-defined service levels govern how the QoS engine treats the targets in order to maintain Mission Critical performance, then Business Critical performance and then Non-critical performance.

The pre-defined service levels also govern how the read-warm cache is getting populated:
Policy 1 – Mission Critical – 1 hit per 1MB Region
Policy 2 – Business Critical – 4 hits per 1MB Region
Policy 3 – Business Critical – 16 hits per 1MB Region
Policy 4 – Non-Critical – read-warm disabled
Policy 5 – Non-Critical – read-warm disabled

The pre-defined service levels also govern how read-ahead is used:
Policy 1 – Mission Critical – enabled
Policy 2 – Business Critical – enabled
Policy 3 – Business Critical – enabled
Policy 4 – Non-Critical – read-ahead disabled
Policy 5 – Non-Critical – read-ahead disabled