The Quality of Service (QoS) feature enables you to set different performance levels (such as I/O rate and transfer rate) for individual volumes or groups of volumes (QoS groups). With server virtualization and cloud services, storage systems are being shared by multiple services. On public clouds, a multi-tenant configuration in which multiple companies (services) coexist can be created, while on private clouds, a configuration in which applications with different business importance coexist can be created. In these configurations, the performance level required for storage varies for each service (application). For normal (non-QoS) storage system settings, if there is an application that requests excessive I/O processing, the storage system operates to run I/O processing in the order of the requests, which tends to reduce the performance level for other applications. By using QoS to control I/O processing on a per-volume or per-QoS group basis, you can reduce performance interference among applications and provide a pre-determined level of performance and quality.
QoS provides the following functions:
- Upper-limit control
- Controls the performance upper limit for host I/O requests on the specified volumes or groups of volumes.
- Lower-limit control
- Controls the performance lower limit for host I/O requests on individual volumes.
- QoS priority control
- Controls the I/O processing priority levels for individual volumes or groups of volumes.
- QoS monitor
- Displays the performance information of the volumes and volume groups subject to the QoS functionality.
- QoS alert
- Monitors the threshold value for the volumes and volume groups subject to the QoS functionality.
The QoS software comes already installed as a basic feature of the storage system.