Home > Storage > PowerStore > Storage Admin > Dell PowerStore: Best Practices Guide > Block storage resources
Block storage resources are accessed through Fibre Channel, NVMe over Fibre Channel, iSCSI, or NVMe over TCP protocols. A host should only access a block resource using one of these protocols at a time. It is not recommended for the same host to access the same block resource using more than one protocol.
PowerStore block storage resources are accessed using ALUA/ANA active/optimized or active/non-optimized paths between the host and the two nodes within the PowerStore appliance. I/O is normally sent on an active/optimized path. PowerStore automatically chooses one of the nodes for the active/optimized path, when the volume is mapped to the host, to maintain a balanced workload across the nodes. This characteristic is called node affinity and can be viewed in PowerStore Manager and modified with PSTCLI or REST. These changes take effect immediately and are nondisruptive if the host is correctly configured for multipathing.
Introduced in PowerStoreOS 2.1, the node affinity of block storage resources will be dynamically rebalanced between nodes to maintain relatively consistent utilization, latency, and performance between both nodes of an appliance. This feature is only available to block storage resources that have not had the node affinity manually set by means of PSTCLI or REST. If the node affinity was manually set, the volume must be unmapped and then remapped to the host, which will reset the affinity to the system selected. This impacts multipathing only; the system does not need to trespass any volume between nodes.
All block storage resources in a PowerStore system have a defined performance policy. By default, this policy is set to Medium. The performance policy does not have any impact on system behavior unless some volumes have been set to Low Performance Policy, and other volumes are set to Medium or High. During times of system resource contention, PowerStore devotes fewer compute resources to volumes with Low Performance Policy. Reserve the Low policy for volumes that have less-critical performance needs.