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Chapter 9. Configuration planning 187
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.
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.
Note: Disk Magic is available to IBM sales representatives and IBM Business Partners
only.