PowerFlex: How to replace a node member in the MDM Cluster

If you have an extra server to replace the current server, then there is no need to change the cluster mode (3-node or 5-node). If you do not have an additional server, you must reduce the cluster mode, from 5-node to 3-node, or from 3-node to single node.

Add or replace a server to the MDM cluster.

Before you begin, perform the following: Assign the necessary IP addresses to the replacement server.

Install the MDM package on the server.

In this example, we are replacing the server whose IP address is 10.3.1.179, currently a member of a 5-node MDM cluster, with a server whose IP address is 10.3.1.57, which is currently external to any PowerFlex system. This process can be used to replace any role in the MDM cluster.

Steps

1- Log in to the Primary MDM with admin login. use single quotes ' ' if password has special characters

3.x 
scli --login --username admin --password '<password>'

4.x 
scli --login --username admin --password '<password>' --management_system_ip <pfmp_ip>

2- Check that the current server (179) is not the primary MDM by running the following command:

scli --query_cluster

The output similar to the following is displayed:

# scli --query_cluster
Cluster:
Mode: 5_node, State: Normal, Active: 5/5, Replicas: 3/3
Master MDM:
Name: mdm17, ID: 0x5d07497754427fd0
IPs: 10.3.1.17, 192.168.1.17, Management IPs: 10.3.1.17, Port: 9011
Version: 2.0.972
Slave MDMs:
Name: mdm19, ID: 0x26ee566356362451
IPs: 10.3.1.19, 192.168.1.19, Management IPs: 10.3.1.19, Port: 9011
Status: Normal, Version: 2.0.972
Name: mdm18, ID: 0x5843c4d16d8f1082
IPs: 10.3.1.18, 192.168.1.18, Management IPs: 10.3.1.18, Port: 9011
Status: Normal, Version: 2.0.972
Tie-Breakers:
Name: mdm179, ID: 0x7380b70e2f73d346
IPs: 10.3.1.179, 192.168.1.179, Port: 9011
Status: Normal, Version: 2.0.972
Name: mdm20, ID: 0x6dfe1c5f4062b5b3
IPs: 192.168.1.20, 10.3.1.20, Port: 9011
Status: Normal, Version: 2.0.972

In this case, Node name mdm179 is a tiebreaker.

3- If the current server is the primary MDM, change its state using the switch_mdm_ownership command

For PowerFlex 3.5 See Dell EMC PowerFlex v3.5.x CLI Reference Guide  

For PowerFlex 4.X See Dell PowerFlex 4.5.x CLI Reference Guide  

4- Make the replacement MDM server a standby MDM, and assign it a name (mdm57, in our example) by running the following command, on the primary MDM:

scli --add_standby_mdm --mdm_role tb --new_mdm_ip 10.3.1.57,192.168.1.57 --new_mdm_management_ip 10.3.1.57 --new_mdm_name mdm57

5- You can see the result of the command by running the following command:

scli --query_cluster

The output similar to the following is displayed:

# scli --query_cluster
Cluster:
Mode: 5_node, State: Normal, Active: 5/5, Replicas: 3/3
...
Tie-Breakers:
Name: mdm179, ID: 0x7380b70e2f73d346
IPs: 10.3.1.179, 192.168.1.179, Port: 9011
Status: Normal, Version: 2.0.972
Name: mdm20, ID: 0x6dfe1c5f4062b5b3
IPs: 192.168.1.20, 10.3.1.20, Port: 9011
Status: Normal, Version: 2.0.972
Standby MDMs:
Name: mdm57, ID: 0x073e4c8b1d20d124, Tie Breaker
IPs: 10.3.1.57, 192.168.1.57, Port: 9011
mdm57 has been added as a standby MDM. When it is a standby MDM, it can be added to the cluster.

6- Replace the current mdm179 with the standby mdm57 by running the following command:

scli --replace_cluster_mdm --remove_tb_name mdm179 --add_tb_name mdm57

The following output is displayed:

Successfully replaced the cluster MDM

The current server has been replaced.

Configure and Customize Dell PowerFlex v3.6.x

In PowerFlex 3.6 we use the terms Master MDM and Slave MDM

#scli --switch_cluster_mode --cluster_mode 3_node --remove_slave_mdm_name  --remove_tb_name  --
#scli --switch_cluster_mode --cluster_mode 5_node --add_slave_mdm_name   --add_tb_name 

In PowerFlex 4.X we use the terms Primary MDM and Secondary MDM 

#scli --switch_cluster_mode --cluster_mode 3_node --remove_secondary_mdm_name  --remove_tb_name 
#scli --switch_cluster_mode --cluster_mode 5_node --add_secondary_mdm_name --add_tb_name