How does the Failover function work?

If files are written to the main unit with protocol for replication, the main unit copies fils to the backup unit.
Supported protocols for replication are the followings.

• Windows shared file (SMB, CIFS)
• Apple shared file (AFP)
• SFTP/FTP/FTPS
• NFS 

Conditions to judge that unexpected error occurs to the main unit.

In case either of the followings occurs, the backup unit will be promoted to the main unit

• In case the backup unit can not recognize the main unit for specific length of time.
  
  At the default setting, the buckup unit checks the main unit once every 60 seconds. If the backup unit can not recognize the main unit 5 times in succession, it judges that unexpected error occurs to the main unit.*1
  Even if it is not defected, when it can not check the unit 5 times in succession due to network issue, it judges that unexpected error occurs to the main unit. In such case, you have to configure Failover function again over the web admin interface of former main unit.*2
  　 
• When the following error occurs to the main unit.
  
  E12 Cooling error.E13 RAID is in degraded mode.
  E14 RAID failed to be mounted.
  E15 Many invalid sectors on hard drive.
  E16 Hard drive can not be detected.
  E22 Hard drive can not be mounted.
  E23 Hard drive is broken.
  E30 Hard drive is brocken./needs to be replaced.
  
  When the above error occurs, the main unit shuts down automatically.
  

*1 To change settings, click [Advanced Settings] and change them on the popped up window.
*2 Error cods you migjt recieve when the backup unit is promoted to the main unit.

When the main unit is rebooted, E27 will disappear. However you need to cancel and reconfigure Failover.
To check how to reconfigure Failover, click here.

File copy (replication) Failure

If file copy (replication) from the main unit to the backup unit is failed for some reasons, the following (I33) will be displayed on LCD of main unit.

Replication　I33
ReplicateFailure

If the file configuration is synchronized between the main and the backup unit, I33 will disappear.
<How to synchronize>
Log in the web admin interface of main unit.
Navigate to [System]-[Backup]-[Replication], and click on [Resynchronize].

* The [Resynchronize] button is active (enable to click) only when it is possible to synchronize with the replication target (buckup unit).
　When the button is inactive, it might become active after waiting for a while.

* If an issue occurs on the network between LCD backup unit and main unit. the backup unit might be promoted to the main (LCD might dilplay "I49")when "I33" appears on the main unit LCD.
　In this case, the [Resynchronize] will not be active. You have to reconfigure Failover from the begining.

How to reconfigure the Failover function

If device or hard disk is broken, please apply to get it repaired.
After repairing, or if it is not broken, follow the procedure below to reconfigure the Failover function.

1. Confirm that "I33" is shown on LCD display of the main unit.
   If "I33" is shown, Failover configuration can not be modified. (can not be canceled)
   Reboot TeraStation, or press power button twice to turn it off and then boot it again.
   
   If "I33" is not shown, go on to the step 2.
   
2. Confirm that the backup unit is running instead of the main unit.
   If the backup unit is running instead of the main unit, IP address is same as the former main unit's one.
   Change the IP address of backup unit (working as main unit)..
   
3. Click [Failover Stop] or [Failover Force Stop] on the web adimin interface of main TeraStation to cancel Failover.
   
4. Configure the Failover function.
    See the answer for howto configure.