Dell PowerVault MD3400 series Deployment Manual

Also see for PowerVault MD3400: Getting started guide Owner's manual

Contents

Dell PowerVault MD3400 series Deployment Manual Manual pdf 26 page image

5Load BalancingLoad Balance PolicyMulti-path drivers select the I/O path to a virtual disk through a specific RAID controller module. Whenthe multi-path driver receives a new I/O to process, the driver tries to find a path to the current RAIDcontroller module that owns the virtual disk. If the path to the current RAID controller module that ownsthe virtual disk cannot be found, the multi-path driver migrates the virtual disk ownership to thesecondary RAID controller module. When multiple paths to the RAID controller module that owns thevirtual 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 hostinterfaces are configured.NOTE: For more information on Load Balance Policy, see your operating system’s manual andupdates.You can choose one of the following load balance policies to optimize I/O performance:• Round robin• Least queue depth• Least path weight (Microsoft Windows operating systems only)Round Robin With SubsetThe round robin with subset I/O load balance policy routes I/O requests, in rotation, to each availabledata path to the RAID controller module that owns the virtual disks. This policy treats all paths to the RAIDcontroller module that owns the virtual disk equally for I/O activity. Paths to the secondary RAIDcontroller module are ignored until ownership changes. The basic assumption for the round-robin policyis that the data paths are equal. With mixed host support, the data paths might have different bandwidthsor different data transfer speeds.Least Queue DepthThe least queue depth policy is also known as the least I/Os or least requests policy. This policy routesthe next I/O request to a data path that has the least outstanding I/O requests queued. For this policy, anI/O request is simply a command in the queue. The type of command or the number of blocks that areassociated with the command are not considered.The least queue depth policy treats large block requests and small block requests equally. The data pathselected is one of the paths in the path group of the RAID controller module that owns the virtual disk.Least Path WeightThe least path weight policy assigns a weight factor to each data path to a virtual disk. An I/O request isrouted to the path with the lowest weight value to the RAID controller module that owns the virtual disk.26

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