HP Hitachi Dynamic Link Manager Software - Manual (Page 35)

• 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 an I/O is issued.
The path that is used is determined by the following:
¢
Round Robin
The paths are simply selected in order from among all the connected
paths.
¢
Least I/Os
The path that has the least number of I/Os being processed is
selected from among all the connected paths.
¢
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.
If the data is not sequential, these algorithms select the path to be used
each time an I/O request is issued.
¢
Extended Round Robin
The paths are simply selected in order from among all the connected
paths.
¢
Extended Least I/Os
The path that has the least number of I/Os being processed is
selected from among all the connected paths.
¢
Extended Least Blocks
The path that has the least number of I/O blocks being processed is
selected from among all the connected paths.
Table 2-5 Features of the Load Balancing Algorithms on page 2-16 describes
the features of the load balancing algorithms.
HDLM Functions
2-15
Hitachi Dynamic Link Manager User Guide (for Windows(R))