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7.13 Mirror Disk DR

7.13 Mirror Disk DR

2015/10/22

Mirror Disk DR resource enables replicate a mirror disk set of a cluster to an offsite node of disaster recovery purpose.
Mirror Disk DR agent act as to mirror disk status and role.
Dynamic information like status and roll of Mirror Disk DR is logged into system event log, this is sent to MCCS by MCCS Event Module.
MCCS Event Module is activated when MCCS service starts.
Data replication software operates by creating mirror set for volumes between two nodes.
Source volume is sit on Primary node, Target volume is sit on Secondary node in a cluster and offsite DR node.
Client is only available to read/write in the source volume, changed block of the volume is replicated to the target volume through the TCP/IP network connection. At this point, target volume is in lock state and read/write is not allowed. This is to ensure data integrity by preventing the use of target volume.


Table of Contents

[Figure] Mirroring Configuration

 

 

Mirror Mode

Mirror mode 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 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 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

Add the mirror disk DR 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.
     

  2. Select 'MirrorDisk DR' from Resource Type lists and click 'Next' button. When add a resource from the mirror disk DR resource type name, this step will be skipped.

  3. Select the mirror volume 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)

        


    [Figure] Mirror Disk DR Resource Added

       

  4. Select IP address of mirror disk and offsite DR.

     

  5. Select mirror type.

    Be careful that when you set to synchronous mode, this cannot be changed to asynchronous mode.
    You can select the mirror type in a cluster at Local Mirror Configuration and offsite DR at Remote server.

    Sync mode : Write I/O will may be delayed depend to network band, but there is no data loss involved.
    Async mode : Relatively faster than the synch mode but it does not guarantee that target data is identical to its source when meet disaster.

     

  6. As 'Additional Settings', Check Disk option is available.


    [Figure] check disk option

     

  7. When click OK button, following popup message appear.
    Confirm selected server as source.
    If you select wrong sever, clock cancel button.

     
    [Figure] Alert popup message after click OK button  

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

 

Deleting

 

Select resource type → right click → delete resource.

 

  1. Click "Delete resource" and a confirming message about deleting resource will appear.


    [Figure] check resource view    

  2. Click "OK" and a confirming message about deleting redundancy program of mirror configuration will. 


    [Figure] Delete physical mirror disk view   

  3. Click "OK" and redundancy program is deleted. Click "Cancle" and only mirror disk DR is deleted. 
    The deleted resource will immediately disappear from the management web console.

 

 

 

 

 

Status