m21res01

Copyright 2013 EMC Corporation. All rights reserved.

This module covers Data Mover failover, including Data Mover Failover, Test Data Mover Failover and Failback.

1 Data Mover Failover


This lesson covers Data Mover failover, including the failover process, how stand by Data Movers work, and planning for Data Mover failover.



The failover process consists of a Primary Data Mover failing and a designated Standby Data Mover being activated as a spare to take the Primarys place. If a Primary Data Mover becomes unavailable, the Standby assumes the MAC and IP addresses of the Primary Data Mover and provides seamless and uninterrupted access to its file systems.

Creating a Standby Data Mover ensures continuous access to file systems. When a Primary Data Mover fails over to a Standby, the Standby Data Mover assumes the identity and functions of the failed Data Mover.

To act as a Standby server, a Data Mover must first be configured as a Standby for one or more Primary Data Movers. For example, you can have one Standby Data Mover acting as a Standby for three other active Data Movers. If one of the Primary Data Movers fails over, the Standby Data Mover assumes the IP and MAC addresses and functions of the failed Data Mover. The former Standby is now a Primary and is no longer available in a Standby capacity.

The Standby Data Mover must have the same type of network interface cards (NICs) as the Data Mover with which it is associated. Any FTP, archive, or Network Data Management Protocol (NDMP) sessions that are active when the failure occurs are automatically disconnected and must be manually restarted.



To detect a Data Mover failure, the Control Station monitors the various conditions of all Data Movers through the redundant internal networks that connect the Control Station to each Data Mover. If the Control Station detects a failure, it responds according to the policy type established when the Standby relationship was created.

If the problem persists, and if CallHome or Email Home is configured, the Control Station calls EMC Customer Service or your service provider with a notification of the event and diagnostic information.

Note: If the Control Station is not running, Data Mover failover cannot occur. When the Control Station returns to service, it will recognize the Data Mover failure and initiate the appropriate action depending on the automatic, retry, or manual failover policy.



When any failover condition occurs, you can transfer functionality from the Primary to the standby Data Mover without disrupting the availability of the file system. The standby Data Mover assumes the following identities from the faulted Data Mover:

Network identity IP and MAC addresses of all its NICs

Storage identity File systems controlled by the faulted Data Mover

Service identity Shares and exports controlled by the faulted Data Mover

The Standby Data Mover assumes user file system services (if the policy is set to automatic) within a few seconds of the failure, transparently, and without requiring users to unmount and remount the file system.

The definition of failover is the process of immediately routing data to an alternate data path or device to avoid interrupting services in the event of a failure. The impact to service is dependent on the applications ability to handle the change gracefully. During normal operation, the VNX Control Station continually monitors the status of all Data Movers. If a Primary Data Mover fails, the Control Station detects the failure via the NAS Master Control Daemon communication over the dedicated network. It instructs the Standby Data Mover to take over as Primary while forcing the original Primary, if it is still running, into a failed state.

Once failover is enacted, the Standby Data Mover becomes the Primary and resumes the entire identity of the failed Data Mover. In most cases, this process should have little, or no noticeable effect on user access to data.

The Data Mover failover process works the same way in systems with two Control Stations. In the event of a Primary Control Station failure the Standby Control Station assumes the Primary role and it is responsible for the Data Mover failover.



The Standby Data Mover is a hot-spare for the Primary Data Movers, and Can act as a spare for up to 7 primaries (depending on model). The recommended ratio is one Standby for every three Data Movers. For maximum availability, configure one Standby for each Primary. A two Data Mover VNX is pre-configured with server_3 as a Standby for server_2.



The failover policy determines how a standby Data Mover takes over after a primary Data Mover fails. The Control Station invokes this policy when it detects the failure of the primary Data Mover

The following are the three failover policies from which you can choose when you configure Data Mover failover:

Auto: The VNX Control Station immediately activates the standby Data Mover (default policy).

Retry: The VNX Control Station first tries to recover the primary Data Mover by resetting (rebooting) it. If the recovery fails, the Control Station activates the standby.

Manual: The Control Station shuts down the primary Data Mover and takes no other action. The standby must be activated manually It can only be configured using CLI.



To prepare the Data Mover for configuration first you must determine how many Standby Data Movers you are going to use, and ensure they are configured to support their corresponding Primary Data Mover(s).

Check that the Primary Data Movers and the corresponding Standbys have the same network hardware components.

Ensure that the Standby Data Mover is free from all networking and file system configurations (there should be no IP configurations set for the network interfaces).

Prior to configuration, check the Ethernet switch to verify that the switch ports of the Primary Data Movers are assigned to the same VLANs as the Standby Data Mover and set to the same speed/duplex. In addition, verify that any LACP/Link aggregation configuration related to the ports for the Primary Data Movers is identical for the Standby.

If Primary Data Mover is connected to a port configured with Jumbo frames then the Standby Data Mover should be connected to ports with the same configuration. Also, if a Standby Data Mover will be supporting multiple Primary Data Movers, the Standby Data Mover must support one network configuration shared by all Primary Data Movers.



In order to configure server_3 as a Standby Data Mover for server_2 using Unisphere follow the steps below:

To configure server_3 as the Standby for server_2:

1. From Unisphere screen select System > Hardware > Data Movers.

2. Right click on the highlighted Data Mover and click Properties

3. From the Role drop-down menu, select primary

4. From the Standby Movers options list, check the desired Standby from the list

5. Select the desired policy from the Failover Policy drop-down menu.

6. Click Apply.

Note: server_3 reboots.



This lesson covered Data Mover failover, including the failover process, how stand by Data Movers work, and planning for Data Mover failover.



This lesson will demonstrate how to test, restore and delete Data Mover failover configuration.



It is important to test Data Mover failover to ensure that, if needed, the Data Movers properly failover and clients can properly access their file systems by way of the Standby Data Mover, which is now acting as a Primary Data Mover. If any network or Operating System environmental changes are made, ensure that the Standby Data Mover(s) still provide client access to their file systems.



It is recommended that you periodically test the functionality of the Data Mover failover configuration. Testing a Data Mover involves manually forcing a failover. Run the following CLI command from either Unisphere or a SSH connection to the Control Station:

server_standby activate mover

Example:

To force server_2 to failover to its Standby Data Mover, use the following command:

server_standby server_2 -activate mover

server_2:

replace in progress ..done

commit in progress (not interruptible)...done

server_2: renamed as server_2.faulted.server_3

server_3: renamed as server_2

Note: The Primary Data Mover is renamed to server_2.faulted.server_3 (OriginalPrimary.faulted.OriginalStandby)and the Standby Data Mover assumes the name of the failed Primary.



After a failover has occurred and any issues that caused the failover have been corrected, or after completing a Data Mover failover test, restore the failed Data Mover back to its Primary status using the restore option. This slide shows how to use Unisphere to restore a Data Mover after a failover.



You can delete a failover relationship at any time. The interface on the left shows how to delete a Standby relationship. All you have to do here is uncheck the Standby Data Mover. The interface on the right shows how to change the role of the Standby Data Mover to Primary.

Note: If the Data Mover is a Standby for more than one Primary, you must remove the relationship for each Data Mover. The Data Mover that was previously the Standby will reboot.



This lesson demonstrated how to test, restore and delete Data Mover failover configuration.



This module covered Data Mover failover, including Data Mover Failover, Test Data Mover Failover and Failback..



This course covered all the key elements of managing and integrating VNX Block and File Infrastructure. That includes integrating VNX block and File access for open systems hosts (Linux and Windows) as well as ESXi hosts through FC and iSCSI connectivity and NFS and CIFS/SMB respectively. This course also covered initial storage system configuration and security using Unisphere tool. The course also covered configuration of local replications solutions for both block and file envronments.


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