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Server Priority Manager allows you to limit the number of I/Os requests from
development servers to the storage system. Server Priority Manager also
allows you to limit the size of data that should be transferred between the
development servers and the storage system. Production servers can expect
reduced response time. Production server performance can be maintained at a
higher level.
Throughout this document, the term upper limit control is used to refer to an
act of limiting performance of low-priority host servers in order to maintain
high-priority host servers at a higher level.
Upper-Limit Control
Upper-limit control can help production servers to perform at higher levels, but
it is not necessarily useful when production servers are not busy.
For example, if the number of I/Os from production servers greatly increases
from 9:00 a.m. to 3:00 p.m. and decreases significantly after 3:00 p.m.,
upper-limit control would suppress 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.
Server Priority Manager provides a function called threshold control. If
threshold control is used, upper limit control is automatically disabled when
traffic between production servers and the storage system decreases to a
certain level. A threshold is a value that indicates the timing at which upper
limit control is disabled. For example, if a threshold of 500 IO/s (500 I/Os per
second) is applied to the entire storage system, development servers are free
from the limit on the I/O rate (i.e. the number of I/Os per second) when the
number of I/Os from all the production servers is below 500 IO/s. If the
number of I/Os from the production servers increases and exceeds 500 IO/s,
upper limit control is restored to limit the number of I/Os from the
development servers again.
The threshold can be used to control the I/O rate (the number of I/Os per
second) or the transfer rate (the size of data transferred per second). For
example, if a threshold of 20 MB/s (20 megabytes per second) is set to a
storage system, the I/O rate limit for development servers is disabled when
the amount of data transferred between the storage system and all the
production servers is below 20 MB/s.
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Hitachi Universal Storage Platform V/VM Hitachi Performance Manager User's Guide
About Performance Manager Options
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