HP StorageWorks XP Remote Web Console Software - Manual (Page 11)

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, disk 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 disk arrays and limit the
amount of data transferred between development servers and disk 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 disable 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 disk 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 disk 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
a disk array, the I/O rate limit for development servers is disabled when the amount of data transferred
between the disk 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 disk 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.