Server Priority Manager allows you to set upper limits of the number of accesses from the server to storage system as well as the amount of data transfer. The upper limits are automatically disabled when the traffic between the server and storage system drops to user-defined levels. Server Priority Manager supports Fibre Channel and iSCSI ports connected to open-systems hosts.
By using Server Priority Manager, you can designate prioritized ports (for example, for production servers) and non-prioritized ports (for example, for development servers) and set upper limits and thresholds for the I/O activity of these ports to prioritize I/O operations to host servers requiring high-throughput I/O operations and prevent low-priority activities from negatively impacting high-priority activities.
You can also control the I/O priority for individual volumes (LDEVs) in a storage system by using CCI. When you use CCI to configure LDEV-level Server Priority Manager operations, you can specify an LDEV and a WWN or iSCSI name of a host adapter. Within a single storage system, you can use only one of the following two methods to set I/O priority level: you can specify ports (GUI or CLI), or you can specify LDEVs (CLI only). For important information about using CCI to perform Server Priority Manager operations, see the Command Control Interface Command Reference.
Performance of high-priority hosts
In a SAN environment, the storage system is usually connected with many host servers. Some types of host servers often require higher performance than others. For example, production servers such as database and application servers that are used to perform daily tasks of business organizations usually require high performance. If production servers experience decreased performance, productivity in business activities can be negatively impacted. To prevent this from happening, the system administrator needs to maintain the performance of production servers at a relatively high level.
Computer systems in business organizations often include development servers, which are used for developing, testing, and debugging business applications, as well as production servers. If development servers experience decreased performance, development activities can be negatively impacted, but a drop in development server performance does not have as much negative impact to the entire organization as a drop in production server performance. In this case, you can use Server Priority Manager to give higher priority to I/O activity from production servers than I/O activity from development servers to manage and control the impact of development activities.
Using Server Priority Manager you can limit the number of I/O requests from servers to the storage system as well as the amount of data that can be transferred between the servers and the storage system to maintain production server performance at the required levels. This practice of limiting the performance of low-priority host servers is called upper-limit control. The upper-limit control is automatically disabled when traffic between the servers and the storage system drops to user-defined levels called thresholds.
While upper-limit control can help production servers to perform at higher levels during periods of heavy use, it may not be desirable when production servers are not busy. For example, if the I/O activity on production servers is high between 09:00 and 15:00 hours and decreases significantly after 15:00, upper-limit control for development servers may not be required after 15:00.
To address this situation Server Priority Manager provides threshold control in which upper-limit control is automatically disabled when I/O traffic between production servers and the storage system decreases to a user-specified level. This user-specified level at which upper-limit control is disabled is called the threshold. You can specify the threshold as an I/O rate (number of I/Os per second) and a data transfer rate (amount of data transferred per second).
For example, if you set a threshold of 500 I/Os per second to the storage system, the upper-limit controls for development servers are disabled when the I/O rate of the production servers drops below 500 I/Os per second. If the I/O rate of the production servers goes up and exceeds 500 I/Os per second, upper-limit control is restored on the development servers.
If you also set a threshold of 20 MB per second to the storage system, the upper-limit controls for development servers are disabled when the amount of data transferred between the storage system and the production servers is less than 20 MB per second.
Requirements for using performance functions
- Performance management products: The following software products are required for performance management operations.
- Hitachi Performance Monitor
- Hitachi Server Priority Manager
- Cache Residency Manager
- Hitachi Virtual Partition Manager
- Access: Administrator access for
Hitachi Device Manager - Storage Navigator or write access for the performance management software products is required to perform operations. Users without Administrator access or write access can only view the performance management information and settings. You need the specific administrator roles for each function:
- Performance Monitor: Storage Administrator (Performance Management)
- Server Priority Manager, Cache Residency Manager, Virtual Partition Manager: Storage Administrator (System Resource Management)
- License keys: The license keys for the performance management software products must be installed. For details about installing license keys, see the System Administrator Guide.
- Java: Java is required for Server Priority Manager and Cache Residency Manager. For details about installing Java and configuring Device Manager - Storage Navigator, see the System Administrator Guide.
- Hitachi Device Manager - Storage Navigator secondary windows: Secondary windows must be enabled before you use Server Priority Manager or Cache Residency Manager. Java and some settings of Hitachi Device Manager - Storage Navigator are required for the Hitachi Device Manager - Storage Navigator secondary window. For details, see the System Administrator Guide.
- Cache memory for Cache Residency Manager: Use of Cache Residency Manager might require additional cache memory in your storage system. For details, see Estimating cache size for Cache Residency Manager.
- Cache memory for Virtual Partition Manager: Use of Virtual Partition Manager might require additional cache memory in your storage system.