IBM DS8000 manual Disk Magic, Size of cache storage, Number of host ports/channels, Remote copy

9.6.1 Disk Magic

An IBM representative or an IBM Business Partner can model your workload using Disk Magic before migrating to the DS8000. Modelling should be based on performance data covering several time intervals, and should include peak I/O rate, peak R/T and peak (read and write) MB/second throughput. Disk Magic will provide insight when you are considering deploying remote technologies such as Metro Mirror. Consult your sales representative for assistance with Disk Magic.

Note: Disk Magic is available to IBM sales representatives and IBM Business Partners only.

9.6.2 Size of cache storage

Having adequate cache storage to sustain your peak workload is imperative for consistent disk system performance. The cache storage is divided into write cache and persistent cache. The DS8100 Model 921 offers up to 128 GB of processor memory and the DS8300 Models 922 and 9A2 offer up to 256 GB of processor memory. In addition, the Non-Volatile Storage (NVS) scales to the processor memory size selected, which can also help optimize performance.

9.6.3 Number of host ports/channels

You should plan to have an adequate number of host ports or channels to provide the required bandwidth to support your workload. The ports must also be balanced across the entire DS8000. FICON ports are faster and more efficient than ESCON ports.

9.6.4 Remote copy

If the DS8000 is a primary disk system in a remote copy configuration, it will consume more resources, such as cache and channels, compared to a standalone disk system, and planning should be done accordingly.

9.6.5 Parallel Access Volumes (z/OS only)

Configuring the DS8000 with PAV will minimize or eliminate IOSQ delays and improve disk performance. PAV can either be static or dynamic. Dynamic PAV should be implemented when possible, as this provides more flexibility. z/OS Workload Manager (WLM) will manage the PAV devices as a group, instead of having a static relationship with the base device. In a static relationship the base device cannot borrow a PAV device from another base device that is not in use. In a dynamic environment, idle PAV devices are assigned to base devices that need more PAV devices to manage the workload. WLM manages the PAV devices on an LSS group level.

9.6.6 I/O priority queuing (z/OS only)

I/O priority queuing allows the DS8000 series to use I/O priority information provided by the z/OS Workload Manager to manage the processing sequence of I/O operations.

9.6.7 Monitoring performance

A number of monitoring tools are available to measure the performance of your DS8000 once it is installed into your configuration.

Chapter 9. Configuration planning 187