HP StorageWorks Performance Control XP user guide (T1605-96007, October 2007)

Performance Control XP user guide 11
1 Performance Control XP
Use Performance Control XP to ensure that I/O operations for hosts requiring high performance receive
higher priority than I/O operations for other hosts.
Optimal performance of high-priority hosts
In a storage area network (SAN) environment, arrays are usually connected to several host servers. Some
types of host servers might require high performance, while the performance of other hosts is less critical.
For example, production servers, such as database servers and application servers, perform daily
business tasks requiring top performance. When performance of these servers drops, productivity in
critical business activities decreases. Therefore, system administrators must maintain performance of
production servers at optimal levels.
Computer systems in business organizations often include lower-priority servers, such as development
servers. Development servers are used for developing, testing, and debugging business applications. If
performance levels of development servers drops, developers are unhappy, but the productivity of critical
business applications is not affected. Therefore, production servers are given higher priority than
development servers.
Use Performance Control XP to limit I/O requests from development servers to arrays and limit the amount
of data transferred between development servers and arrays. Production servers can expect faster
response times and better performance.
Throughout this chapter, the term upper limit control refers to limiting performance of low-priority host
servers to maintain performance of high-priority host servers.
Automatically disabling upper limit control
While upper limit control improves performance of production servers, it is not always useful. Upper limit
control is not required when production servers are not busy. For example, if the number of production
server I/O operations is very high from 9:00 a.m. to 3:00 p.m. and decreases sharply thereafter, upper
limit control suppresses performance of development servers even after 3:00 p.m. Development servers
should be free from upper limit control when production servers are not busy.
Performance Control XP provides a function called threshold control that automatically disables upper limit
control when traffic between production servers and arrays decreases to a certain level. A threshold is a
value indicating the conditions at which upper limit control is disabled. For example, if you apply a
threshold of 500 IO/s (500 I/O operations per second) to the entire array, the I/O rate of development
servers is not limited when the number of I/Os from all production servers is below 500 IO/s. If the
number of production server I/Os increases beyond 500 IO/s, upper limit control is restored to limit the
number of I/Os from development servers.
The threshold can control the I/O rate (number of I/Os per minute) or transfer rate (amount of data
transferred per second). For example, if a you set a threshold of 20 MB/s (20 megabytes per second) for
an array, the I/O rate limit for development servers is disabled when the amount of data transferred
between the array and all production servers is below 20 MB/s.
Overview of Performance Control XP procedures
The procedure for using Performance Control XP depends on the type of connection established between
host bus adapters (HBAs) and array ports. For one-to-one connections between HBAs and ports, use the
Port tab of the Performance Control pane. For many-to-many connections between HBAs and ports, use
the WWN tab of the Performance Control pane.