Dell PowerFlex 4.5.x Administration Guide

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:

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.