PowerFlex How to replace an MDM Cluster node member

Summary: Replace a member of an MDM cluster to replace a faulty server or change the server IP address.

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Instructions

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.

NOTE:

It is not recommended to use single mode in production systems, except in temporary situations.

The following rules are true regardless of the circumstances:
  • To remove a cluster member, you first must make it a standby, then remove the standby. To add a member to a cluster, you first make it a standby, then add the standby to the cluster.
  • The cluster must always have 5, 3, or 1 members, never any other amount. For a further understanding of this subject, see "The MDM cluster" in the Architecture section of Getting to Know Dell PowerFlex Guide. Go to the section that describes your environment:
    • "Replace a cluster member by adding a new server"
    • "Replace a cluster member without adding a new server to the cluster"

 

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- 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, server 179 is a tiebreaker.

2- 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 | Dell US 

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

3- 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

4- 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.

5- 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.

Additional Information

Configure and Customize Dell PowerFlex v3.6.x | Dell US

 

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

Affected Products

PowerFlex rack, ScaleIO
Article Properties
Article Number: 000249601
Article Type: How To
Last Modified: 03 Feb 2025
Version:  2
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