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Service levels for PowerMaxOS provide open-systems customers with the ability to separate applications based on performance requirements and business criticality. You can specify service levels to ensure that your highest-priority application response times are not affected by lower-priority applications.
Service levels address an organization’s requirement to ensure that applications have a predictable and consistent level of performance while running on an array. The available service levels are defined in PowerMaxOS and can be applied to an application’s storage group at any time, which enables the storage administrator to initially set and change the performance level of an application as needed. A service level is applied to a storage group using the PowerMax management tools: Unisphere for PowerMax, REST API, Solutions Enabler.
You can use service levels with host I/O limits to make application performance more predictable while enforcing a specified service level. Setting host I/O limits enables you to define front-end port performance limits on a storage group. These front-end limits can be set by IOPS, host Mb per host, or a combination of both. You can use host I/O limits on a storage group that has a specified service level to throttle IOPS on applications that are exceeding the expected service-level performance.
PowerMaxOS provides six service levels to choose from, as shown in the following table:
Service level | Expected average response time |
Diamond (highest priority) | 0.6 milliseconds |
Platinum | 0.8 milliseconds |
Gold | 1 millisecond |
Silver | 3.6 milliseconds |
Bronze (lowest priority) | 7.2 milliseconds |
Optimized | N/A |
Diamond, platinum, and gold service levels have an upper limit response time but no lower limit, ensuring that I/O is serviced as fast as possible. Silver and bronze service levels have both an upper limit and a lower limit to allow higher-priority IOPS to be unaffected.
Storage groups that are set to “Optimized” are throttled for higher-priority IOPS on all service levels aside from bronze.
Note: PowerMaxOS service levels and host I/O limits are available at no additional cost for both PowerMax and VMAX All Flash systems that are running PowerMaxOS 5978.
For more information, see the Dell EMC PowerMax: Service Levels for PowerMaxOS White Paper.
The following table shows the service-level objective (SLO) configurations that Dell Technologies recommends for different SAP HANA installation types:
Installation type | SLO | Reason |
SAP HANA persistence (data and log) for production installations | Diamond | Diamond ensures that the PowerMax system tries to keep the latency below 1 millisecond, which is an SAP requirement for small (4 KB and 16 KB) block sizes on the log volume. Using the diamond SLO with all-flash devices provides the following benefits:
|
SAP HANA persistence for nonproduction installations | Gold | Although the SAP performance KPIs do not apply to SAP HANA nonproduction installations, those installations are still critical components in an overall SAP landscape. |
SAP HANA installation | Bronze | Bronze is sufficient when you are using PowerMax File in a PowerMax array to provide the NFS share for the SAP HANA installation file system (/hana/shared). |
Operating system boot image | Bronze | The operating system boot image can also reside on a bronze SLO. |
In highly consolidated environments, SAP HANA and other databases and applications compete for storage resources. PowerMax arrays can provide the appropriate performance for each application when the user specifies SLOs and workload types. By using different SLOs for each such application or group of applications, it is easy to manage a consolidated environment and modify the SLOs when business requirements change. See Host I/O limits and multitenancy for additional ways of controlling performance in a consolidated environment.
Service levels enable you to insulate specific storage groups from any performance impact from other “noisy neighbor” applications. You can assign critical applications to higher service levels such as diamond, platinum, or gold, which allow these storage groups to use all available resources at all times. These critical applications are not managed unless the system exhibits resource constraints that cause the applications to fail to maintain required performance levels.
The quality of service (QoS) feature that limits host I/O was introduced in the previous generation of VMAX and PowerMax arrays. The feature offers PowerMax 2500 and 8500 customers the option to place specific IOPS or bandwidth limits on any storage group, regardless of the SLO assigned to that group. For example, assigning a host I/O limit for IOPS to a storage group of noisy SAP HANA neighbors with low performance requirements can ensure that a spike in I/O demand does not affect the SAP HANA workload and performance.