Resynchronization

During the resynchronization of a DRBD resource, DRBD determines where the latest data resides. In most cases the Source of the synchronization is the primary server (ISP) and the state of the resource instance on the secondary server is Resyncing – Target. When the synchronization Source is the secondary server, the state of the instance on the secondary server is Resyncing – Source.

While resynchronization is in-progress the LifeKeeper GUI reflects the status on the secondary server (not ISP) with the following icon:

When the primary server (ISP) is the source of the resynchronization, the DRBD resource on the primary server (where the resource is ISP) shows the following icon:

When the primary server (ISP) is the target of the resynchronization, the DRBD resource on the primary server (where the resource is ISP) shows the following icon:

As soon as the resynchronization is complete, the resource state on the secondary server becomes UpToDate and the icon changes to the following:

And the icon for the DRBD resource on the primary server will be:

The following points should be noted about the resynchronization process:

• A DRBD resource and its parent resources cannot fail over to a target that was in the synchronization process when the primary failed and is the source of the synchronization.
• If your DRBD resource is taken out of service during synchronization, the synchronization may be stopped depending on the DRBD_TAKE_DOWN_ON_REMOVE setting in the /etc/default/LifeKeeper file. When DRBD_TAKE_DOWN_ON_REMOVE is set to 0 (the default value), the resource IS NOT taken down when the resource is taken out of service. Synchronization will continue. If DRBD_TAKE_DOWN_ON_REMOVE is set to 1 then the resource IS taken down and synchronization is stopped. If synchronization is stopped then the target of the synchronization will not be “UpToDate” and will require access to the “UpToDate” data to be brought in-service. If LifeKeeper is stopped in such a way that all resources are taken out of service (i.e., not using ‘lkstop -f’), synchronization will always be stopped. Synchronization will automatically resume when the resource is brought in-service.
• If the server that is the “source” of the synchronization becomes inoperable during the synchronization process, any target server that is in the synchronization process will not be able to bring your DRBD resource into service. Once the server that is the source of the synchronization becomes functional again, a resynchronization of the mirror will continue.