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[Figure] Mirroring Configuration

Data sync

Mirroring is classified into a sync mode and an async mode depending on the time of response to a request for saving.

Async mode

A response to writing on the mirror volume is immediately sent after the source volume is saved. Since it does not wait until data is sent to the target volume and saved there, the response time is very fast. However, in case of trouble, it can cause data mismatches due to data failed to be transmitted at that time.

Sync mode

When there is a request for writing to the disk, it will be written to the target volume as soon as it is written to the source volume. The final, successful response to a request for writing is achieved after both the source and the target volume are written. The response time is slow, but there exists the same data for the source and the target all the times.

Add

Add the DR shared disk resource. Before you can add the shared disk DR resource, you must install a copy tool at the remote server that data will be copied to.

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  1. Select the group -> Right click with the mouse -> Add the resource.   

  2. In resource wizard, select a shared disk DR and click the Next button. 

  3. The shared volume set of resource wizard will display the drive characters that can be used to compose the shared disk DR and the existing drive characters that are already configured.
    You cannot inquire about information at the remote server. So, you need to enter IP addresses on your own. 

    Warning

    The drive characters to be used as the shared disk DR should be same on the both servers that compose a cluster. Data will be copied to the target node from the source node. The remote server cannot be the source. Be careful when you select the drive character where data exists. If you try to add the existing mirror volume, <mirrored> will be added to the volume letter.



      [Figure] Shared Disk DR Resource Added


  4. Click the 'Additional Setup' to define the synch mode and the disk test option.

    Info

    <Sync mode> Once selected, the sync mode cannot be reversed. So, be careful.
    Sync mode : Response is slow but there is no data loss involved. Async mode : Relatively faster than the sync mode but it can suffer from data loss.
    <Disk test option> Set the disk test command option. For more details on the function, refer to MSDN.

     
     [Figure] Shared Disk DR Additional Setting


  5. Press the Finish button after adding the shared disk DR resource, the following warning screen will be displayed.
    Check again if it is the correct source server selected.
    If not, then click on the 'Cancel' button and set it again. 


    [Figure] The warning screen displayed when you press the Finish button after adding the shared disk DR resource   
     

  6. Click the 'Finish' button to add the shared disk DR resource. You can immediately check the result in the management web console.

 

Delete

Select the resource -> Right click with the mouse -> Delete the resource.
The deleted resource will immediately disappear from the management web console.   

Status

The following table explains the status changing of the MCCS resource caused by a user's command and the status. 
The command assumes that it is generated by a user.

Shared disk DR agent: Manages the mirror disk. Copying program should be installed. 

Status

Agent's functions

Description

Note

Online

In this status, you can access the source volume and perform a writing test properly.

 

Offline

Regardless of the mirror role, the LOCKVOLUME command is used to lock the volume. If the mirror volume is not defined, the LOCKVOLUME command is ignored and regarded as a failure.

 

Monitoring

Before monitoring, update the status of resource first. Perform a disk write test to determine the status of resource.
If the writing test is successful, it is regarded as the online state. If the writing test failed on the disk, it is regarded as the offline state.

 

Offline

Except for the online and trouble states, it is always offline.

 

Online

Type of operation is determined by the role of the mirror volume at the start node.
<Source volume> 1. You can unlock and write the volume. 2.To unlock, you can use the 'UNLOCKVOLUME' menu in the copy program. Check whether there are dirty bits.
<Target or NONE volume> 1. If the mirror role is target or NONE volume, run the SWITCHOVERVOLUME command.

 

Monitoring

Refer to the description of monitoring as above.

 

Trouble


If a writing test failed online, or an attempt to go online is failed, the trouble state is displayed.
*Failover deactivation state When a mirror network communication failure, target node or target disk failure occurs, the mirror state is changed from 'MIRRORING' to other, such as 'MIRROR_PAUSED'. If the mirror status is not 'MIRRORING', a failover will take place and it can cause data losses or damages. To prevent this problem, an agent deactivates the failover mode if the mirror status is not "MIRRORING". If the failover mode is deactivated, no failover will take place even if manual failover or troubles occur. If mirror network communication failures are recovered, and communication resumes, it will automatically perform RESYNC. When the mirror status is changed to MIRRORING, the failover mode will be also automatically activated.

 

Online

Refer to the above online command.

 

Offline

Regardless of the mirror role, the LOCKVOLUME command is used to lock the volume. If the mirror volume is not defined, the LOCKVOLUME command is ignored and regarded as a failure.

 

 
 

Attribute

Show the unique attribute of the shared disk DR resource.

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