[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.

Semi-sync mode

With semi-synchronous mirroring, each write is captured and transmitted to the target system. Local write completes in the source as soon as the replication packet has reached the target. Normally, no writes are lost in case of failover , but this may can be lost when both nodes are failed simultaneously.

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 resource to a group.

1. When add a resource from a group name, select a group → right click → 'Add Resource'
    
2. Select 'MirrorDisk' from Resource Type lists and click 'Next' button. When add a resource from the MirrorDisk resource type name, this step will be skipped.
   
   
3. Select the source server and mirror volume
   
   

4. 메타디스크 볼륨을 선택합니다. 

   메타디스크 볼륨은 드라이브 레터를 붙일 수 있는 별도의 볼륨이 필요합니다. 이런 볼륨을 만들기 위해서는 아래의 경우가 준비 되어야 합니다.

   1. 드라이브레터
      예 : m

   2. 디렉토리 마운트
      예 : C:\vdrive
   3. GUID 형태의 볼륨 이름
      예 : \\?\Volume{ed8a8f02-18b3-11e6-91b4-000c29ac57f8}\
   4. VHD(Virtual Hard Disk)
      예:
        1. m c:\r0_meta.vhd # VHD + 레터 방식
        2. C:\vdrive c:\r0_meta.vhd # VHD + 디렉토리 마운트 방식
        3. \\?\Volume{ed8a8f02-18b3-11e6-91b4-000c29ac57f8}\  c:\r0_meta.vhd # VHD + GUID 방식

   외부 메타 데이터 볼륨

   메타 볼륨은 별도의 볼륨을 생성할 때 반드시 포맷을 하지 않고 RAW 상태로 만들어야 합니다. WDRBD는 기본적으로 섹터 단위로 메타 볼륨에 접근하기 때문에 NTFS와 같은 파일시스템으로 포맷을 하게되면 부트레코드(Boot Record) 영역으로의 접근이 쓰기 권한을 요구하게 되며 해당 영역이 보호를 받게 되어 일부 섹터에 대한 접근이 되지 않습니다. 또한 MFT 같은 파일시스템의 메타 영역이 생성되어 WDRBD에서 메타디스크로 사용할 수 없게 됩니다. 따라서 초기 볼륨 생성시 포맷 하지 않는 옵션을 선택하여 생성해야 합니다.

   

   
   

   
   

   
   [Figure] Mirror Disk Added
   

    

5. When click OK button, following warning message will be displayed and click 'OK' button if the informations are correct.
    
   [Figure] Alert popup message after click OK button
   
   
6. Click the 'Finish' button to add the mirror disk resource 

Deleting

Select resource type → right click → delete resource.0

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 the mirror configuration will appear.
   
   [Figure] Deleting mirror disk view
   
   
3. Click "OK" and mirror disk is deleted.
   확인을 클릭하면 모두 삭제, 취소를 클릭하면 MCCS 에 구성된 미러디스크 리소스만 삭제하게 됩니다
   

State

The following table explains the state of mirror disk resource.

미러 디스크 에이전트: 미러 디스크를 관리하며, 복제 프로그램이 설치되어 있어야 합니다. 

Attribute

Show the specified attribute of mirror disk resource.

※ 속성 값은 해당 리소스를 등록할 때에 입력된 값이며, '리소스 고유 속성'에서 값을 변경하거나 확인할 수 있습니다.