Proper system and storage sizing must be performed before deployment of any new PowerFlex clusters. Replication adds additional sizing concerns. Your Dell Technologies technical sales resources have access to a system sizing utility. The PowerFlex sizing utility takes inputs including workload characterization, replication footprint, and WAN bandwidth and quality, as well as network design and infrastructure.

Additional cluster setup requirements for adding asynchronous replication include:

• A way for the clusters participating in replication to communicate securely
• Grouping of volume pairs into consistency groups
• Testing methods for potential failures or even distributing workload without affecting the primary application
• Configuration of the physical WAN network for external replication when the target cluster is in another data center
• Additional IP addresses for replication activity

This paper addresses all these topics.

Exchange of storage cluster Certificate Authority root certificates

PowerFlex system root CA certificates must be exchanged between replicating clusters to protect from possible security attacks. Because exchanging certificates is a security-sensitive issue, this step is performed using the PowerFlex command-line interface. On each system, a certificate is created and sent to the other host in the replicated pair.

The following command extracts the certificate from the cluster:

scli --extract_root_ca --certificate_file /tmp/sys0.cert

Next, copy the certificate to the partner system. To import the certificate, on the partner system, we use a command of the following form:

scli --add_trusted_ca --certificate_file /tmp/sys0.cert --comment Site-A

Peering storage clusters

Peering is the next required step before configuration of replicated volume pairs. Peering establishes the data paths and communication between two PowerFlex systems. You can use PowerFlex Manager to peer systems, but you first need one piece of critical information—the system IDs. You can use the PowerFlex CLI to capture the system IDs for both storage clusters. The act of logging in to the PowerFlex CLI and authenticating to the cluster reveals the cluster ID. You will need the IDs from both the source and the target systems.

Figure 6.   Capturing a PowerFlex system ID

Note: PowerFlex version 4.0 supports up to four peer systems from a single source system. All systems must be at version 4.0. A volume can be a member of at most one replication pair (RCG)..

To begin peering:

1. In PowerFlex Manager, go to the Protection menu, and click the down arrow to expand the menu.

Figure 7.   Protection menu

2. Select Peer Systems, and then click Add Peer System.

Figure 8.   Add Peer System

3. Enter the name, remote system ID, and the IP address of the target cluster Primary MDM. Click ADD IP.
4. Add additional IPs if appropriate.
5. Click Add.

Figure 9.   Add Peer System

6. Repeat the preceding steps on the target storage cluster, entering the remote system ID of the primary cluster.

Upon completion, the systems are peered in both directions, and you are ready to start pairing your replicated volumes.