PowerFlex supports load balancing with NVMe over TCP.
Persistent discovery
The persistent discovery controller ensures that the host remains connected to the discovery service after discovery. If at any point there is a change in the discovery information that is provided to the host, the discovery controller returns an asynchronous event notification (AEN) and the host requests the updated
Discovery log page.
Here are some examples of changes in discovery information:
A new volume is mapped to the host from a new protection domain.
A new storage data target (SDT) is added to the system.
Load balancing wants to move the host connection from one storage data target to another.
When configuring NVMe hosts, ensure that every host is connected for discovery at most once per subnet (data IP address subnet). To use this functionality, ensure that the host operating system supports the Persistent Discovery Controller, and that the Persistent Discovery flag is set in the discovery. (See the respective operating system for the NVMe over TCP host configuration.)
NVMe over TCP hosts network awareness
Hosts are connected to the storage through Layer-2 or Layer-3 network. While the storage does not manage or need to be aware of the network configuration, there are some aspects of the network that impact the storage.
Load balancing takes the data network/subnet into consideration to ensure there is a balance between the host connections on each data network with a specific subnet, hence improved performance.
In Layer-3 networks, the system must have routing tables configured.
Multiple objects need to be defined for load balancing to work:
Object
Description
Host subnet
Networks or subnets used to connect hosts to storage, which can be either layer 2 or layer 3 (routed). You might have to define the data networks before starting the deployment itself. Maximum supported data networks are 4 (in
DellPowerFlex appliance and
DellPowerFlex rack) and 8 in the software-only offering.
System data network
System-wide object that applies to all protection domains. Once a resource group is deployed, configure system data networks/subnets to be used to connect hosts initiator to the storage data target. Maximum allowed system data networks are 8. Configure two or four system data networks for
PowerFlex rack and
PowerFlex appliance. The number that you need depends on the number of
PowerFlex data (SDS-SDS and SDS-SDT communication) networks that are configured for the deployment.
If you have not defined the system data network, by default, a host can reach all system data networks. Ignoring the data networks/subnets may result in unequal load between the host initiator ports and nonoptimized I/O performance with the
PowerFlex system. In addition, it may impact the path resiliency if not all the host initiator ports can connect to the system. For Layer-3 networks, the system must have routing tables configured.
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