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arcserve-KB : Using Computer Name Alias Redirection with a CA XOsoft File Server HA Scenario

Last Update: 2015-12-15 22:07:53 UTC

XOSOFT Replication: 12.5
Last Modified Date:    03/17/2010
Document ID:    TEC510317
Tech Document
Title:  Using Computer Name Alias Redirection with a CA XOsoft File Server HA Scenario

Description:

This document outlines using Computer Name Alias Redirection with a CA XOsoft File Server High Availability (HA) Scenario.

Solution:

If your users are connecting to Network Shares using Mapped Drives, then you need to configure your CA XOsoft File Server HA scenario to use the Switch Host Name method of network traffic redirection.

Mapped drives are establishing their connection to shares using the NetBios Name of the host, NOT DNS resolution. Therefore redirecting DNS will not redirect the mapped drives, because the host names and corresponding NetBios Names are different on the Master and Replica servers. A Switch Host Name method of Network Traffic Redirection will allow the Replica to assume the Host Name and therefore the NetBios Name of the Master. This will then allow your user's mapped drives to be redirected to the Replica after the switchover.

A UNC path of any kind, such as a Mapped Drive or the path \\<host name>\<share name> is using the NetBios Name of the host to resolve the Host Name to an IP address. NetBios broadcasts the request on a subnet. The host then replies providing the necessary info to allow the requesting host to establish a connection.

With the release of CA XOsoft 12.5 SP2 a new feature was released with Computer Name Aliasing. With traditional File Server HA scenarios which use the Switch Host Name Redirection method requires setting 'Reboot After Switchover and Switchback' to ON in order for the active Replica to properly stand in during a switchover as both nodes are physically being renamed.

Computer Name Aliasing will allow the active Replica to stand in for the Master server without being renamed or rebooted. This lowers the complexity of the switchover process and greatly reduces the amount of time needed for the Replica server to become active and service client requests. If reboot is enabled as part of the switchover process (recommended) only the inactive Master will be rebooted once it is renamed with the '-XO' suffix.

NOTE: If the Master server is an Active-Passive cluster the Virtual Network Name is renamed to '<SERVERNAME>-XO' but no reboot will occur even if reboot is enabled within the scenario.

The process flow of a File Server HA scenario switchover with Host Rename (with Reboot after Switchover and Switchback), DNS Redirection (Required when enabling Aliasing) and Use Computer Name Alias enabled (On) is as follows:

  1. Switchover is invoked (Automatically or via push button switchover)
  2. Master Server shares are taken offline.
  3. Master Server is renamed as '<SERVERNAME>-XO'.
  4. Computer Name Alias is added to Replica.
  5. DNS A Record for Master is modified to point to IP Address of Replica.
  6. Master Server is rebooted.
  7. Active Replica Shares are brought online.
  8. Switchover is completed.

Figure 1

As part of the switchover process an OptionalNames value is added to the registry of the Replica under HKEY_LOCAL_MACINE\SYSTEM\ControlSet001\Services\lanmanserver\parameters which is the name of the Master Sever (FS-M). This setting allows the Replica to accept user requests to the Master's UNC when made active.

Figure 2

If you receive the following error on a forward scenario where the Master is Active, the above value (OptionalNames) was not properly cleared on the Replica from a previous switchback from the Replica to the Master:

Figure 3

Clearing the Optional Names Value or selecting the replica node and running a Recover Active Server > Make Master Active from the Tools Menu will allow for the Forward Scenario to run.

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