How to configure SAN replication between IBM Storwize V3700 systems


The Metro Mirror and Global Mirror Copy Services features enable you to set up synchronous and asynchronous replication between two volumes between two separate IBM storage, so that updates are made by an application to one volume in one storage systems in prod site are mirrored on the other volume in anther storage systems in DR site.

  • The Metro Mirror feature provides a synchronous-replication. When a host writes to the primary volume, it does not receive confirmation of I/O completion until the write operation has completed for the copy on both the primary volume and the secondary volume. This ensures that the secondary volume is always up-to-date with the primary volume in the event that a failover operation must be performed. However, the host is limited to the latency and bandwidth limitations of the communication link to the secondary volume.
  • The Global Mirror feature provides an asynchronous-replication. When a host writes to the primary volume, confirmation of I/O completion is received before the write operation has completed for the copy on the secondary volume. If a failover operation is performed, the application must recover and apply any updates that were not committed to the secondary volume. If I/O operations on the primary volume are paused for a small length of time, the secondary volume can become an exact match of the primary volume.

Prerequisites:

  1. Both systems are connected via dark fibre, L2 MPLS or IPVPN for replication over IP
  2. Both systems are connected via fibre for replication over FC.
  3. Both systems have up to date and latest firmware.
  4. Easy Tier and SSD installed in both systems.
  5. Remote Copy license activated in both systems.
  6. Volumes are identical in Prod and DR SAN.

Configure Metro Mirror in IBM v3700 Systems

Step1: Activate License

Log on to IBM V3700>Settings>System>Licensing

Activate Remote Copy and Easy Tier License.

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Step2: Configure Ethernet Ports & iSCSI in Production SAN and DR SAN

Both systems will communicate via management network but volume will be replicated via Ethernet if remote copy is configured to use replication over Ethernet. This step is necessary for Metro Mirror over Ethernet. Skip this step if you are using FC.

Log on to Production IBM v3700 systems. Settings>Network>Ethernet Ports. Right Click on Node1 Port 2> Configure Copy Group1 and Copy Group2. Assign IP address, Enable iSCSI, Select Copy Group1. Repeat to Create Copy Group2.

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Repeat the step to configure Copy Groups in DR SAN.  
Note: TCP/IP assigned in DR SAN can be from same subnet of production SAN or can be different than production subnet as long as both subnets can communicate with each other.  
Step3: Create Partnership in Prod & DR SAN
Log on to Production V3700>Copy Services>Partnerships>Create Partnership>Add NetBIOS Name and Management IP of DR SAN

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Fully Configured Indicates that the partnership is defined on the local and remote systems and is started.

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Initial synchronization bandwidth is 2048MBps but once I take the DR storage to DR site. I will modify that to 1024MBps. Initial Synchronization will take place in prod site. You can have your own bandwidth specification.

Log on to DR V3700>Copy Services>Partnerships>Create Partnership>Add NetBIOS Name and Management IP of Prod SAN

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Step4: Create Relationships between Volume

log on to Prod SAN>Copy Services>Remote Copy>Add Relationship>Select Metro Mirror

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Specify DR SAN as Auxiliary Systems where DR Volume is located. IBM should have used word “Master/Slave” or “Prod/DR systems”.   

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Add identical volume>Click Next.

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Step5: Monitor Performance and Copy Services

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Consistency group states

Consistent (synchronized) – The primary volumes are accessible for read and write I/O operations. The secondary volumes are accessible for read-only I/O operations.

Inconsistent (copying) – The primary volumes are accessible for read and write I/O operations, but the secondary volumes are not accessible for either operation. This state is entered after the startrcconsistgrp command is issued to a consistency group in the InconsistentStopped state. This state is also entered when the startrcconsistgrp command is issued, with the force option, to a consistency group in the Idling or ConsistentStopped state.

The background copy bandwidth can affect foreground I/O latency in one of three ways:

  • If the background copy bandwidth is set too high for the intersystem link capacity, the following results can occur:
    • The intersystem link is not able to process the background copy I/Os fast enough, and the I/Os can back up (accumulate).
    • For Metro Mirror, there is a delay in the synchronous secondary write operations of foreground I/Os.
    • For Global Mirror, the work is backlogged, which delays the processing of write operations and causes the relationship to stop. For Global Mirror in multiple-cycling mode, a backlog in the intersystem link can congest the local fabric and cause delays to data transfers.
    • The foreground I/O latency increases as detected by applications.
  • If the background copy bandwidth is set too high for the storage at the primary site, background copy read I/Os overload the primary storage and delay foreground I/Os.
  • If the background copy bandwidth is set too high for the storage at the secondary site, background copy write operations at the secondary overload the secondary storage and again delay the synchronous secondary write operations of foreground I/Os.
    • For Global Mirror without cycling mode, the work is backlogged and again the relationship is stopped

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Once volumes are synchronized you are ready to integrate storage with System Center 2012 R2.

Further Readings:

SAN Replication based Enterprise Grade Disaster Recovery with ASR and System Center

What’s New in 2012 R2: Cloud-integrated Disaster Recovery

Understanding IT Disaster Recovery Plan

Install and Configure IBM V3700, Brocade 300B Fabric and ESXi Host Step by Step

About Raihan Al-Beruni

My Name is Raihan Al-Beruni. I am working as an Infrastructure Architect in Data Center Technologies in Perth, Western Australia. I have been working on Microsoft technologies for more than 15 years. Other than Microsoft technologies I also work on Citrix validated solution and VMware data center virtualization technologies. I have a Masters degree in E-Commerce. I am certified in Microsoft, VMware, ITIL and EMC. My core focus is on cloud technologies. In my blog I share my knowledge and experience to enrich information technology community as a whole. I hope my contribution through this blog will help someone who wants more information on data center technologies.
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4 Responses to How to configure SAN replication between IBM Storwize V3700 systems

  1. Raj says:

    Hi, I have configured as per document . It was working for few days and suddenly stop partnership. Now I want to stop but it doesn’t show stop tab. IT show Health status in error mode in both Storage. It does not working. Bandwidth is 20 MBPS at Primary site and 6 MBPS at secondary sideIt gives error code 2020 ip remote copy link unavailable. We are able to ping both storage from both side.

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    • Have you configured the storage asynchronous mode? It seems you don’t have enough bandwidth for replication. IBM recommend having minimum 10MB/s dedicated link for asynchronous mode. You may be sharing your bandwidth with other traffic. That’s why link was showing not available.

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  2. Pasquale Colella says:

    Thank you for the article. Do you need to use a Flashcopy of each lun at the primary site or able to replicate off the production lun?

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