IBM DS8880 Series, Introduction And Planning Manual

Page: 62 / 244

v Transaction Processing Facility (TPF)
v
Virtual Storage Extended/Enterprise Storage Architecture
v z/OS
v z/VM
®
v z/VSE
®
For the most current information on supported hosts, operating systems, adapters,
and switches, go to the IBM System Storage Interoperation Center (SSIC) website
(www.ibm.com/systems/support/storage/config/ssic).
I/O load balancing
You can maximize the performance of an application by spreading the I/O load
across processor nodes, arrays, and device adapters in the storage system.
During an attempt to balance the load within the storage system, placement of
application data is the determining factor. The following resources are the most
important to balance, roughly in order of importance:
v Activity to the RAID drive groups. Use as many RAID drive groups as possible
for the critical applications. Most performance bottlenecks occur because a few
drive are overloaded. Spreading an application across multiple RAID drive
groups ensures that as many drives as possible are available. This is extremely
important for open-system environments where cache-hit ratios are usually low.
v Activity to the nodes. When selecting RAID drive groups for a critical
application, spread them across separate nodes. Because each node has separate
memory buses and cache memory, this maximizes the use of those resources.
v Activity to the device adapters. When selecting RAID drive groups within a
cluster for a critical application, spread them across separate device adapters.
v Activity to the Fibre Channel ports. Use the IBM Multipath Subsystem Device
Driver (SDD) or similar software for other platforms to balance I/O activity
across Fibre Channel ports.
Note: For information about SDD, see IBM Multipath Subsystem Device Driver
User's Guide (http://www-01.ibm.com/support/
docview.wss?uid=ssg1S7000303). This document also describes the product
engineering tool, the ESSUTIL tool, which is supported in the
pcmpath
commands and the datapath commands.
Storage consolidation
When you use a storage system, you can consolidate data and workloads from
different types of independent hosts into a single shared resource.
You can mix production and test servers in an open systems environment or mix
open systems and IBM Z hosts. In this type of environment, servers rarely, if ever,
contend for the same resource.
Although sharing resources in the storage system has advantages for storage
administration and resource sharing, there are more implications for workload
planning. The benefit of sharing is that a larger resource pool (for example, drives
or cache) is available for critical applications. However, you must ensure that
uncontrolled or unpredictable applications do not interfere with critical work. This
requires the same workload planning that you use when you mix various types of
work on a server.
50
DS8880 Introduction and Planning Guide