HP P9500 Bedienungsanleitung PDF herunterladen (Seite 35)

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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 is 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.

The following table lists and describes the features of the load balancing

algorithms.

Table 2-4 Features of the Load Balancing Algorithms

Algorithm type Algorithm features

•

Round Robin

• Least I/Os

• Least Blocks

These types of algorithms are most effective when a lot of

discontinuous, non-sequential I/Os are issued.

• Extended Round

Robin

• Extended Least I/Os

• Extended Least

Blocks

If there is a read request for I/O data that is sequential with

the data of the I/O that was issued immediately beforehand,

an improvement in reading speed can be expected due to the

storage system cache functionality. These types of

algorithms are most effective when many continuous I/Os

are issued (the I/O data is sequential).

Some I/O operations managed by HDLM can be distributed across all

paths, and some cannot. Thus, you should be aware that even if you

specify the Round Robin algorithm, I/O operations cannot always be

allocated uniformly across all paths.

By default, the Extended Least I/Os algorithm is set when HDLM is first

installed. When an upgrade installation of HDLM is performed, the existing

setting is inherited.

Select the load balancing algorithm most suitable for the data access patterns

in your system environment. If there are no recognizable data access

patterns, we recommend applying the Extended Least I/Os algorithm.

You can specify the load balancing function by the dlnkmgr command's set

operation. For details on the set operation, see

set (Sets Up the Operating

Environment) on page 6-17.

HDLM Functions

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