HP Hitachi Dynamic Link Manager Software - Manual (Page 42)

2. HDLM Functions
20
Table 2-4: Features of the Load Balancing Algorithms
#
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 6.6 set (Sets Up the Operating
Environment).
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).