Hitachi XP P9500 User Manual page 28

Extended Round Robin
Extended Least I/Os
Extended Least Blocks
Most Recently Used (VMware)
Round Robin (VMware)
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.
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.
You can specify the load balancing function by the dlnkmgr command's set
operation. For details on the set operation, see
Environment) on page
2-10
Table 2-4 Load Balancing Algorithms
Algorithm name
6-15.
HDLM Functions
Hitachi Dynamic Link Manager User Guide (for VMware(R))
PSP name
HTI_PSP_HDLM_EXRR
HTI_PSP_HDLM_EXLIO
HTI_PSP_HDLM_EXLBK
VMW_PSP_MRU
VMW_PSP_RR
set (Sets Up the Operating