Using truck based replication
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Using truck based replication

In order to preseed a remote node with data which is then to be kept synchronized, and to skip the initial device synchronization, follow these steps.

[Note]Note

This assumes that your local node has a configured, but disconnected DRBD resource in the Primary role.

That is to say, device configuration is completed, identical drbd.conf copies exist on both nodes, and you have issued the commands for initial resource promotion on your local node — but the remote node is not connected yet.

  1. On the local node, issue the following command: 

    drbdadm -- --clear-bitmap new-current-uuid resource

  2. Create a consistent, verbatim copy of the resource's data and its metadata. You may do so, for example, by removing a hot-swappable drive from a RAID-1 mirror. You would, of course, replace it with a fresh drive, and rebuild the RAID set, to ensure continued redundancy. But the removed drive is a verbatim copy that can now be shipped off site.

    If your local block device supports snapshot copies (such as when using DRBD on top of LVM), you may also create a bitwise copy of that snapshot using dd.

  3. On the local node, issue: 

    drbdadm new-current-uuid resource

    Note the absence of the --clear-bitmap option in this second invocation.

  4. Physically transport the copies to the remote peer location.

  5. Add the copies to the remote node. This may again be a matter of plugging a physical disk, or grafting a bitwise copy of your shipped data onto existing storage on the remote node.

    Be sure to restore or copy not only your replicated data, but also the associated DRBD metadata. If you fail to do so, the disk shipping process is moot.

  6. Bring up the resource on the remote node: 

    drbdadm up resource

After the two peers connect, they will not initiate a full device synchronization. Instead, the automatic synchronization that now commences only covers those blocks that changed since the invocation of drbdadm -- --clear-bitmap new-current-uuid.

Even if there were no changes whatsoever since then, there may still be a brief synchronization period due to areas covered by the Activity Log being rolled back on the new Secondary. This may be mitigated by the use of checksum-based synchronization.

[Tip]Tip

You may use this same procedure regardless of whether the resource is a regular DRBD resource, or a stacked resource. For stacked resources, simply add the -S or --stacked option to drbdadm.

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The initial device synchronization Home Part III. Working with DRBD