78 Appendix—Load Balancing
Least Queue Depth With Subset
The least queue depth with subset policy is also known as the least I/Os or
least requests policy. This policy routes the next I/O request to a data path
that has the least outstanding I/O requests queued. For this policy, an I/O
request is simply a command in the queue. The type of command or the
number of blocks that are associated with the command are not considered.
The least queue depth with subset policy treats large block requests and small
block requests equally. The data path selected is one of the paths in the path
group of the RAID controller module that owns the virtual disk.
Least Path Weight With Subset
The least path weight with subset policy assigns a weight factor to each data
path to a virtual disk. An I/O request is routed to the path with the lowest
weight value to the RAID controller module that owns the virtual disk. If
more than one data path to the virtual disk has the same weight value, the
round-robin with subset path selection policy is used to route I/O requests
between the paths with the same weight value. The least path weight with
subset load balance policy is not supported on Linux operating systems.
Changing Load Balance Policies on the Windows Server 2008 Operating System
Load balancing with the MD3200i series storage array is only available for
Windows Server 2008 and later versions of the operating system. You can
change the load balance policies from the default round robin with subset by
using either the:
•Device manager
• Disk management
To change the load balance policy using Windows Server 2008 device manager:
1
From the desktop of the host, right-click
My Computer
and select
Manage
to open the
Computer Management
dialog.
2
Click
Device Manager
to show the list of devices attached to the host.
3
Right-click on the multi-path disk device for which you want to set the
load balance policies, then select
Properties
.
4
From the
MPIO
tab, select the load balance policy that you want to set for
this disk device.
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