Windows load balance policy, Round robin with subset, Appendix—load balancing – Dell POWERVAULT MD3620F User Manual

Page 29: Appendix—hardware cabling best practices

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Appendix—Load Balancing

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Appendix—Load Balancing

Windows Load Balance Policy

Multi-path drivers select the I/O path to a virtual disk through a specific

RAID controller module. When the multi-path driver receives a new I/O, the

driver tries to find a path to the current RAID controller module that owns

the virtual disk. If that path cannot be found, the multi-path driver migrates

the virtual disk ownership to the secondary RAID controller module. When

multiple paths to the RAID controller module that owns the virtual disk exist,

you can choose a load balance policy to determine which path is used to

process I/O. Multiple options for setting the load balance policies let you

optimize I/O performance when mixed host interfaces are configured.
You can choose one of the following load balance policies to optimize

I/O performance:

• Round robin with subset
• Least queue depth with subset

Round Robin With Subset

The round-robin with subset I/O load balance policy routes I/O requests, in

rotation, to each available data path to the RAID controller module that

owns the virtual disks. This policy treats all paths to the RAID controller

module that owns the virtual disk equally for I/O activity. Paths to the

secondary RAID controller module are ignored until ownership changes.

The basic assumption for the round-robin policy is that the data paths are

equal. With mixed host support, the data paths might have different

bandwidths or different data transfer speeds.

book.book Page 29 Friday, September 9, 2011 11:26 PM

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