Design on Ramen

CephFS Regional DR Consistency Group

Mon, 01 Jan 0001 00:00:00 +0000

CephFS Regional DR Consistency Group

Summary

Currently, Ramen only supports non-consistency-group CephFS RDR (Regional Disaster Recovery). However, with the upcoming support for consistency groups in CephFS, Ramen can expand its capabilities to include consistency-group RDR for CephFS.

Motivation

Consistency Groups are pivotal in maintaining data integrity during synchronizing related datasets across regions, mitigating the risk of data corruption or loss during failover events. They constitute essential components of Regional Disaster Recovery, enabling organizations to minimize risks and ensure the availability and integrity of their data across geographical locations.

Global VolumeGroupReplication Design Document

Mon, 01 Jan 0001 00:00:00 +0000

Global VolumeGroupReplication Design Document

1. Design

Some storage backends manage replication at the LUN or filesystem level, where all applications sharing the same storage unit belong to a single replication group and must transition state together. Global VGR builds on top of Ramen’s offloaded storage support to coordinate a shared VGR across all VRGs in such a replication group, with multi-level consensus, label propagation, status validation, watchers, and observability through conditions, metrics, and alerts.

Incremental Sync for Consistency Groups

Mon, 01 Jan 0001 00:00:00 +0000

Incremental Sync for Consistency Groups

Extends Cephfs-RDR-ConsistencyGroup.md .

Summary

When drplacementcontrol.ramendr.openshift.io/enable-diff: "true" is set on a DRPC, Ramen preserves VolumeGroupSnapshots across sync cycles and uses the ceph-volsync-plugin External mover to transfer only changed blocks between consecutive snapshots.

Annotation Propagation

DRPC → VRG → RGS (ReplicationGroupSource)
 → RGD (ReplicationGroupDestination)

Follows the same flow as UseVolSyncAnnotation: the user sets the annotation on the DRPC instance, which propagates it to the VRG via ManifestWork. The annotation is whitelisted in constructVRGFromView so it survives hub round-trips. DRPC annotation changes trigger reconcile automatically via the default For(&DRPlacementControl{}) predicate.

VRG Type Sequence

Mon, 01 Jan 0001 00:00:00 +0000

VRG Type Sequence

Overview

RamenDR can use Velero to capture Kubernetes object information. By default, Velero will back up all object types in arbitrary order. However, many applications have internal dependencies that require specific ordering by object type. The VRG Type Sequencer attempts to address this deficiency by taking multiple partial backups, with the order defined a the user.

Example Use Case: Backup

Backup Overview

Take an example Backup that requires the following sequence: