Table of Contents

Tether Sync allows a container to be populated with files and registry keys and then updated later. The Tether Sync feature is useful if you are not able to move some files (e.g., locked databases) right away but instead, need to wait for a service window. In a case like this, Tether Sync allows you to tether as much at the source as possible in advance and then re-connect later during a service window in order to finish the migration. Any new or different files/keys will be re-copied from the source, and files/keys that have been removed from the source will also be removed.

A container must be undocked to apply Tether Sync. An application will not start until the Tether Sync process is complete.

Tether Sync modes are:

• Update

• Reset

Update Mode

Using Update Mode, any files or keys that are newest will be copied. If you changed a file on both the source and destination machines, the newest file will be copied. Changes that have been made to the destination machine may not be preserved in Update Mode. You should therefore keep track of changes that were made to the destination for re-hosting or other reasons because these changes may need to be repeated.

Example Use:

An application has been tethered to a destination machine. Work has been performed on the destination machine, for example testing or re-configuration. Later, when you want to finalize the migration, you re-tether to the original production machine to get any files that have been updated or added. For example, a website installation to which changes have been made. In this case, you would use Update Mode to avoid losing modifications to the destination machine.

Reset Mode

Using Reset Mode, any files or keys that are different between the source and destination machines will be overwritten. Changes that have been made to the container on the destination machine will not be preserved in Reset Mode. You should therefore keep track of changes that were made to the destination for re-hosting or other reasons because these changes will need to be repeated.

Example Use:

An application has been migrated for user acceptance testing (UAT) and has been extensively exercised. It's possible that files have been modified, added, or removed during UAT and these changes are not wanted on the production server. In this case, Reset Mode would return the container to the original state it was in and copy any additional changes from the source machine.

Caution:

VirtaMove does not recommend that you perform a Tether Sync in Reset Mode for an IIS application migration. This mode will undo all changes, including any modifications made by IIS migration scripts. IIS services may not start if you perform a Tether Sync in Reset Mode for an IIS application migration.

What Gets Synced?

Tether Sync does not synchronize everything on the source machine to the destination machine. Only paths and keys that have previously been tethered will be checked against the source machine. Specifically, individual files that have been copied will be checked against the source machine as well as paths that were copied in entirety (greedy copied).

For example:

If you have a complete copy of "\Program Files\SQL Server" and you add directory "\Program Files\SQL Server\some_folder", then a sync operation will copy "some_folder" to the destination machine because the "SQL Server" folder was greedy copied. If you add "\Program Files\some_other_folder", it will not be copied because it is outside of the paths that were greedy copied.

To see which paths will be synced, see the tether_greedy_roots.dat file in the container folder.  This file contains a list of paths that are meant to be synchronized with the source.

To Use Tether Sync

1. In the Administrative Console, select a container that was previously tethered, and then click the Tether tab.

2. Make sure the container is undocked. Click the Undock button if the container is docked.

3. Make sure that the Use Tether check box is enabled and that the credentials required to connect to the source machine are still valid.

4. In the Sync Mode field, select one of the following as appropriate:

   • None - Do not sync.

   • Update - Any files or keys that are newest will be copied. If you changed a file on both the source and destination machines, the newest file will be copied.

   • Reset - Any files or keys which are different between the source and destination will be overwritten on the destination machine. Any files/keys which are new on the destination will not be preserved. Not recommended for an IIS application migration. 

     Open

     

5. If Sync Mode is Update or Reset, click the Sync Now button.

6. If you selected Reset, read and respond to the warning message by clicking Yes or No.

When a container is syncing, its status will read "Syncing" until the process is complete. An application will not start until the Tether Sync process is complete.

To Use Tether Sync Using the CLI

The mode of sync will be the mode set using the Administrative Console on the Tether tab (Update or Reset) but sync will not take place if the container is docked or CPROP_TETHER_SYNC is not set via virtapedit.

Perform Tether Sync in a command prompt window using virtasync as follows:

Tether Synch Log

After a sync operation, the following file is created in the container directory:

Open

This file contains a log of the operations that occurred during the sync. You can also view the Tether Sync log file on the Appliance Logs tab. See Logging.