Resynchronizing the vFiler unit

About resynchronizing the vFiler unit

Data ONTAP 7.1 introduces a vfiler dr resync command that enables you to resynchronize your original vFiler unit with the currently activated disaster-recovery vFiler unit before bringing up the original vFiler unit. This method not only saves you from deleting the original vFiler unit and creating a new vFiler unit, but also does not require a baseline transfer (involving a large amount of data), which would otherwise occur between the new vFiler unit and the disaster-recovery vFiler unit.

How the vfiler dr resync command works

If the original vFiler unit needs to be resynchronized, the vfiler dr resync command is executed on the storage system on which that vFiler unit exists. If the disaster-recovery vFiler unit has been activated, the resync operation proceeds to update the original vFiler unit. After the update, the resync operation does not activate the original vFiler unit. The original vFiler unit becomes the disaster-recovery vFiler unit and the currently active disaster-recovery vFiler unit continues to serve data.

If you want to switch the roles of the two vFiler units, you must do that by using the vfiler dr activate command on the original vFiler unit.

After the roles have been switched and the original vFiler unit has been reactivated, you can use the vfiler dr resync command on the now deactivated disaster-recovery vFiler unit to synchronize it with the original vFiler unit. The disaster-recovery vFiler unit goes back to being the backup vFiler unit, ready for use if the original vFiler unit goes down.

When the vfiler dr resync command is executed on the storage system on which the disaster-recovery vFiler unit exists, it can issue an update for the existing storage elements and add and remove storage elements from the disaster-recovery vFiler unit.

Note
The vfiler dr resync command does not retrieve any configuration changes that might have been done on the disaster-recovery vFiler unit and preserves the IP information (including DNS and NIS) of the storage system on which the command is run.

Prerequisites for using the vfiler dr resync command

You can use the vfiler dr resync command if the following prerequisites are met:

The storage elements for the vFiler unit are only volumes (traditional or FlexVol) and not qtrees.
The source and destination vFiler units contain identical volumes.
The size of volumes on the source and the destination vFiler units is the same.
The vFiler unit from which you are updating is activated.
The original vFiler unit is not in the process of migration.

Resynchronizing the original vFiler unit

To resynchronize the original vFiler unit on the original storage system with the currently activated disaster-recovery vFiler unit, perform the following steps.

Attention
On the storage system on which you are resynchronizing the original vFiler unit, protect any volumes that have the same names as volumes on the disaster-recovery vFiler unit.

If a volume with the same name exists, the volume is automatically added and initialized for SnapMirror transfers from the disaster-recovery vFiler unit. Any existing data on the newly added volume is lost.

Step	Action
1	Ensure that the original vFiler unit (the one you are trying to resync) is in a stopped state. If not, enter the following command to stop the vFiler unit: vfiler stop vfilername
2	On the original storage system, enter the following command: vfiler dr resync [-l authinfo] [-a alt-remote, alt-local] [-s] dr_vfilername@disaster_recovery_filer authinfo is the authentication information specified in the username:password format. The username is the login name of the administration host on the disaster recovery storage system and the password is the password for that user name. If you do not specify the authentication information in the `vfiler dr resync` command, you are prompted for it when the command is run. alt-remote is the alternate hostname or IP address of the source (the disaster recovery storage system, in this case). alt-local is the alternate hostname or IP address of the destination (the original storage system, in this case). `-s` enables you to set up a synchronous SnapMirror relationship between the source and destination storage systems. dr-vfilername is the name of the disaster-recovery vFiler unit that is currently in the activated state. disaster_recovery_filer is the name of the storage system on which the currently activated disaster-recovery vFiler unit exists. Notes: The `vfiler dr resync` command uses the Data ONTAP SnapMirror feature as its underlying technology. You can set multiple paths from the source to the destination storage systems in SnapMirror. The `-a` option of the `vfiler dr resync` command enables you to set multiple paths for the resync operation. For more information, see the section on using SnapMirror over multiple paths in the Data ONTAP Data Protection, Online Backup and Recovery Guide. The `vfiler dr resync` command resynchronizes all storage elements belonging to the disaster-recovery vFiler unit, including the volumes that were added to the disaster-recovery vFiler unit after it was activated. When you run the `vfiler dr resync` command on the disaster-recovery vFiler unit to resync it with the original vFiler unit, you do not need to specify the `-l`, `-a`, and `-s` options. The values stored when `vfiler dr configure` was run (for a baseline transfer) to back up the original vFiler unit are used.
3	After the resync operation is complete, enter the following command on the storage system on which the original vFiler unit exists to check the status of the vFiler unit that was resynchronized: vfiler status -r original_vfilername The original vFiler unit will be in a stopped, DR backup state. This is because the `vfiler dr resync` command does not activate the vFiler unit upon resynchronizing. The vFiler unit continues to behave like a backup disaster-recovery vFiler unit until you use the `vfiler dr activate` command to reactivate it. For information on how to activate the vFiler unit, see procedure Activating the disaster-recovery vFiler unit.
4	Reinstate the disaster-recovery vFiler unit on the disaster-recovery storage system.
	If...	Then...
	The storage elements for the vFiler unit are only volumes	On the disaster-recovery storage system, enter the following command: vfiler dr resync [-l authinfo] [-a alt- remote, alt-local] [-s] original_vfilername@original_filer For details of the `vfiler dr resync` command, see Step 2 of Resynchronizing the original vFiler unit. You are done.
	The storage elements for the vFiler unit are qtrees	On the disaster-recovery storage system, destroy the disaster-recovery vFiler unit by entering the following command on the disaster-recovery hosting storage system: vfiler destroy vfilername vfilername is the name of the original vFiler unit. On the disaster-recovery storage system, re-create the disaster-recovery vFiler unit. From the original storage system or its replacement, perform the procedure Creating the disaster-recovery vFiler unit.

Handling resyncing failures

If the vfiler dr resync operation is interrupted or does not complete, you must perform the following steps.

Step	Action
1	If...	Then...
	There was a "volume offline or does not exist" error	Make the volume online or create it. Continue with Step 4.
	There were volume resync errors	Perform the steps listed in Reactivating the original vFiler unit using SnapMirror commands. You are done.
	There were no volume resync errors	Continue with Step 2.
2	Enter the following command to check if the vFiler unit you were resyncing exists on the storage system on which you were running the `vfiler dr resync` command: `vfiler status`
3	If the vFiler unit exists, enter the following command to destroy it: vfiler destroy vfilername
4	Enter the following command to re-create the vFiler unit you destroyed earlier: vfiler create -r vfilername pathname
5	Enter the following command to resync the vFiler unit: vfiler dr resync [-l authinfo] [-a alt-remote, alt-local] [-s] dr_vfilername@disaster_recovery_filer For details of the `vfiler dr resync` command, see Step 2 of Resynchronizing the original vFiler unit.