Dell PowerVault MD3260 Series Deployment Manual

Also see for PowerVault MD3260 Series: Manual Getting started guide Configuration guide Installation and configuration guide Hardware and software guide

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Dell PowerVault MD3260 Series Deployment Manual Manual pdf 25 page image

6Appendix — Load BalancingWindows Load Balance PolicyMulti-path drivers select the I/O path to a virtual disk through a specific RAID controller module. When the multi-pathdriver 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 controllermodule. When multiple paths to the RAID controller module that owns the virtual disk exist, you can choose a loadbalance policy to determine which path is used to process I/O. Multiple options for setting the load balance policies letyou 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 subsetRound Robin With SubsetThe round-robin with subset I/O load balance policy routes I/O requests, in rotation, to each available data path to theRAID controller module that owns the virtual disks. This policy treats all paths to the RAID controller module that ownsthe virtual disk equally for I/O activity. Paths to the secondary RAID controller module are ignored until ownershipchanges. The basic assumption for the round-robin policy is that the data paths are equal. With mixed host support, thedata paths may have different bandwidths or different data transfer speeds.Changing Load Balance Policies In Windows Sever 2008Load balancing with the PowerVault MD3260 series is only available for Windows Server 2008 or later versions of theoperating system. You can change the load balance policies from the default round robin with subset by using one of thefollowing:• Device Manager options• Disk Management optionsLeast Queue Depth With SubsetThe least queue depth with subset policy is also known as the least I/Os, or least requests policy. This policy routes thenext I/O request to a data path that has the least outstanding I/O requests queued. For this policy, an I/O request issimply a command in the queue. The type of command or the number of blocks that are associated with the commandare not considered. The least queue depth with subset policy treats large block requests and small block requestsequally. The data path selected is in the path group of the RAID controller module that owns the virtual disk.25

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