Application I/O prioritisation – Quality of Service

A prerequisite for any storage consolidation strategy is the ability to host multiple applications on a single storage platform without allowing the actions of one set of users to affect the I/O performance of others.
Potential problem areas for shared storage access include:

• Workloads with I/O and cache conflicts, such as online transaction processing (OLTP) and data warehousing
• Tiered storage access restrictions, such as development and production applications
• Peak processing demands for critical applications versus maintenance activities, such as backup or database reorganisation

The ETERNUS DX Quality of Service feature with application I/O prioritisation resolves these issues and enables the consolidation of multiple tiers of applications in a single storage system.
It sets performance limits for each connected server according to its priority. By prioritising data access and dynamically managing any I/O conflict, high performance can be guaranteed for high-priority applications, and at the same time capacity is used more efficiently, thus increasing storage utilisation without sacrificing performance. The QoS policies allow the user to specify the expected I/O patterns of each application (random, sequential, read or write-based, and mixed).
An example is shown in the figure below. Two servers are connected to an ETERNUS DX storage system. Server B is granted a higher priority than server A. Accordingly, limits for I/O requests from both servers are set and server B has a higher limit than server A. In the event of increased workloads on the low-priority server A, the system limits the I/O performance at the predefined level and the performance of the high-priority server B is not affected. Thus the required I/O performance is guaranteed regardless of the workloads on other servers with lower priority.

The Quality of Service functionality provides higher degree of automation to ensure simpler and more intuitive settings.
The ETERNUS DX S3 and ETERNUS DX200F set values with ETERNUS SF Storage Cruiser Quality of Service management option based on performance requirements and dynamically adjusts the values along with the result of performance monitoring.
This feature makes it easier for the user to start the settings. Furthermore, the automatic tuning ensures that the values used are more accurate, resulting in better service level fulfillment.

In addition, an upper bandwidth limit of ETERNUS DX S3 and DX200F can be set for each copy path. Even if a specific path fails, a steady load can be maintained without centralising the load to other paths.

Benefits

• Mapping application Service Level Agreements (SLA) to storage infrastructure
• Increased storage utilisation by combining different workload profiles
• Allows service providers to guarantee a specific QoS and charge accordingly

Product requirement