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[Figure] Mirroring Configuration

Replication Mode

Replication option employs both asynchronous and synchronous mirroring schemes. Understanding the advantages and disadvantages between synchronous and asynchronous mirroring is essential to the correct operation of this.

Async Mode

With asynchronous mirroring, each write is captured and a copy of this is made. That copy is queued to be transmitted to the target system as soon as the network will allow it. Meanwhile, the original write request is committed to the underlying storage device and control is immediately returned to the application that initiated the write. At any given time, there may be write transactions waiting in the queue to be sent to the target machine.  But it is important to understand that these writes reach the target volume in time order, so the integrity of the data on the target volume is always a valid snapshot valid snapshot of the source volume at some point in time.  Should the source system fail, it is possible that the target system did not receive all of the writes that were queued up, but the data that has made it to the target volume is valid and usable.

Sync Mode

With synchronous mirroring, each write is captured and transmitted to the target system to be written on the target volume at the same time that the write is committed to the underlying storage device on the source system.  Once both the local and target writes are complete, the write request is acknowledged as complete and control is returned to the application that initiated the write.  With synchronous mirroring, each write is intercepted and transmitted to the target system to be written on the target volume at the same time that the write is committed to the underlying storage device on the source the source system.  Once both the local and target writes are complete, the write request is acknowledged as complete and control is returned to the application that initiated the write.  

Adding

There are two way to add a resource which one is select this from a group name and another is select this from a resource type.

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Add the mirror disk resource to a group.

1. When add a resource from a group name, select a group → right click → 'Add Resource'. Or select Edit(E) from the main menu bar → select 'Add Resource'. Or select 'Add Resource' icon from the tool bar.
   Image Removed [Figure] Adding Resource in Resource Wizard
    
2. Select 'MirrorDisk' from Resource Type lists and click 'Next' button. When add a resource from the mirror disk resource type name, this step will be skipped.
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    [Figure] Select Resource Wizard View
   
3. Next steps are same as adding in resource type.
   

Adding in Resource Type

1. 
   
2. Resourcetype → Right Click → Add Resource.
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     [Figure] Adding resource in a Resource type
   Getting disk information.
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   [Figure] Screen of Getting disk information.
   Select the mirror volume  Select the mirror disk and MCCS will renew the information.

   If you skip enter resource name, this will given 'Mirror_value' which value is selected driver letter.(Ex: Mirror_G)

    

   Warning

   The drive characters to be used as the mirror disk should be same on the both servers. [Drive characters in the SAN environment (shared disk) are also displayed in the list. So, make sure you select the accurate drive characters.] Data will be copied to the target node from the source node. Be careful when you select the drive character where data exists. If you try to add the existing mirror volumedisk, <mirrored> will be added to the volume letter.

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   [Figure] After gathering additional information screen

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   [Figure] When Selecting the Volume With No Mirror Configuration
   

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   [Figure] When Selecting the Volume With Mirror Configuration 
   

   If there is no mirror disk resource to be configured, it will show the following.

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   [Figure] When there is no mirror disk resourceMirror Disk Resource Added

    

3. As 'Additional Settings', Synchronized Mode and Check Disk option is available.

   Info
   <Synchronized Mode> Once selected, the synch 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 synch mode but it can suffer from data loss. <Check Disk Option> Set the check disk command option. For more details on the function, refer to MSDN.

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   [Figure] Defining mirror type and check disk option

    

4. When click OK button, following popup message appear.
   Confirm selected server as source.
   If you select wrong sever, clock cancel button.
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   [Figure] Alert popup message after click OK button
   
   
5. Click the 'Finish' button and to add the mirror disk resource is added.
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   [Figure] Adding mirror disk resource is completed  
   You can immediately check the result in the management web console.

Deleting

Select resource type → right click → delete resource.

1. Select "Delete resource".
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   [Figure] Delete mirror disk resource view
   Click "Delete resource" and a confirming message about deleting resource will appear. 
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   [Figure] check resource view
   
   
2. Click "OK" and a confirming message about deleting redundancy program of mirror configuration will. 
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   [Figure] Delete physical mirror disk view
   
   
3. Click "OK" and redundancy program is deleted. Click "Cancle" and only mirror disk is deleted. 
   The deleted resource will immediately disappear from the management web console.

Status

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

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

Attribute

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[Figure]  Mirror Disk Attribute Screen

Show the unique attribute of resource.

The attribute value is entered to register the resource, and you can change or check it in the 'Specified Attribute'.