HP Hitachi Dynamic Link Manager Software - Manual (Page 30)

Load Balancing Algorithms
The load balancing function uses VMware vSphere PSPs or PSPs provided by
HDLM. The following table lists the load balancing algorithms that HDLM can
use.
Table 2-5 Load Balancing Algorithms
Algorithm name PSP name
Extended Round Robin HTI_PSP_HDLM_EXRR
Extended Least I/Os HTI_PSP_HDLM_EXLIO
Extended Least Blocks HTI_PSP_HDLM_EXLBK
Most Recently Used (VMware) VMW_PSP_MRU
Round Robin (VMware) VMW_PSP_RR
PSPs for the Extended Round Robin, Extended Least I/Os, and Extended
Least Blocks algorithms are installed together with HDLM. 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.
The default algorithm is the Extended Least I/Os algorithm, which is set when
HDLM is first installed. When an upgrade installation of HDLM is performed,
the algorithm that is currently being used is inherited.
Select the load balancing algorithm most suitable for the data access patterns
of your system environment. However, if there are no recognizable data
access patterns, we recommend using the default algorithm, the Extended
Least I/Os algorithm.
2-12
HDLM Functions
Hitachi Dynamic Link Manager User Guide for VMware ®