This article details the Subnet Affinity and Auto Rebalance features and also provides the best practices for their use.

Subnet Affinity

When assigning the server and NIC combination to provide a vDisk to target devices, select from the following subnet settings:

• None:

• Ignore subnets; use least busy server.
• None is the default setting.

• Best Effort:

• Use the least busy server/NIC combination from within the same subnet.
• If no server/NIC combination is available within the subnet, select the least busy server from outside the subnet.
• If more than one server is available within the selected subnet, perform load balancing between those servers.

• Fixed:

• Use the least busy server/NIC combination from within the same subnet.
• Perform load balancing between servers within that subnet.
• If no server/NIC combination exists in the same subnet, do not start target devices assigned to this vDisk.

Auto Rebalance

Rebalance enabled using Trigger Percent:

• Enable to rebalance the number of target devices on each server in the event that the trigger percent is exceeded.

• When enabled, PVS checks the trigger percent on each server approximately every ten minutes.
  For example, if the trigger percent on this vDisk is set to 25%, rebalancing occurs within ten minutes if this server has 25% more load in comparison to other servers that can provide this vDisk.

• This is based on the number of targets currently connected to the server using the specified vDisk.

Note: The load balance algorithm takes into account the PVS Properties of each server when determining the load.

Load balancing will not occur if:

• Less than five target devices are using a particular server.

• The average number of target devices using all qualifying servers is less than five.

• The number of target devices that are starting on a given server is more than 20% of the total number of devices connected to the server (preventing load shift thrashing during a 'boot storm').

Load balancing is considered when target devices start. PVS determines the qualified PVS Server with the least amount of load and provides the vDisk. When a qualified server is brought online, rebalancing will occur automatically.

Note: Enabling both Subnet Affinity and Auto Rebalance might cause a reconnect storm to occur. This could cause the stream process on the PVS server to fail and target devices to become unresponsive.
Citrix does not recommend enabling both features.