HP XP Racks - Manual (Page 32)

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Virtual Storage Platform series
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Hitachi AMS2000 series #
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Hitachi SMS series
¢ HUS100 series #
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This storage system applies when the dynamic I/O path control function is
disabled.
Load Balancing Algorithms
HDLM has the following six load balancing algorithms:
• The Round Robin algorithm
• The Extended Round Robin algorithm
• The Least I/Os algorithm
• The Extended Least I/Os algorithm
• The Least Blocks algorithm
• The Extended Least Blocks algorithm
The above algorithms are divided into two categories, which differ in their
processing method. The following describes both of these processing
methods:
The Round Robin, Least I/Os, and Least Blocks algorithms
These algorithms select which path to use every time a certain number of
I/Os are issued. The path that is used is determined by the following:
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Round Robin
The paths are simply selected in order from among all the connected
paths.
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Least I/Os
The path that has the least number of I/Os being processed is
selected from among all the connected paths.
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Least Blocks
The path that has the least number of I/O blocks being processed is
selected from among all the connected paths.
The Extended Round Robin, Extended Least I/Os, and Extended Least Blocks
algorithms
These algorithms determine which path to allocate based on whether the
data of the I/O to be issued is sequential with the data of the I/O that
was issued immediately beforehand.
If the data is sequential, the path used will be the one to which the data
of the I/O that was issued immediately beforehand was distributed.
However, if a specified number of I/Os has been issued to a path,
processing switches to the next path.
2-12
HDLM Functions
Hitachi Dynamic Link Manager User Guide for AIX®