Journal Manager Prioritization for Near-Zero Latency Data Replication
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Solution Overview
Problem
Conventional replication systems introduce unacceptable latency due to synchronous data writes to replication appliances, impacting service level objectives (SLOs) and efficiency, especially with storage technologies like NVMe, which affects data protection systems' ability to comply with service level agreements (SLAs).
Innovation Solution
A data protection system with smart quality-of-service controls and prioritization mechanisms that optimize resource allocation by using splitters and journal managers to asynchronously transmit data, prioritize workloads based on SLOs, and manage host memory and network bandwidth effectively, ensuring efficient replication operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If synchronous data writes are sent to replication appliances, then data consistency is maintained, but write latency increases significantly
Solution Approach 1:
The patent implements preliminary action by writing data to a journal before replication. The journal manager captures write operations and stores them in a journal buffer, allowing the production storage to acknowledge writes immediately without waiting for replication completion. This preliminary journaling action enables subsequent asynchronous replication to proceed without impacting production write latency.
Solution Approach 2:
The patent introduces a journal manager as an intermediary component between production storage and replication appliances. The journal manager buffers write operations and manages the replication queue, decoupling the synchronous write path from the replication path. This intermediary allows writes to flow through the journal while replication occurs asynchronously, resolving the latency issue while maintaining data consistency through the journal's ordered playback.
2Loss of time
If data is replicated asynchronously to reduce latency, then write performance improves, but data consistency may be compromised
Solution Approach 1:
The journal manager performs preliminary action by capturing and buffering all write operations in a journal before replication. This journal serves as a source of truth that ensures data consistency, while allowing replication to proceed asynchronously at its own pace. The journal's ordered playback mechanism guarantees that replicated data maintains consistency with the production storage state.
Solution Approach 2:
The patent implements continuity of useful action by maintaining a continuous replication stream from the journal to replication appliances. The journal manager continuously drains the replication queue, ensuring that async replication remains ongoing without interruption. This continuous action maintains data consistency while avoiding the latency penalties of synchronous writes.
3Reliability
If replication resources are allocated to ensure data protection, then reliability improves, but available resources for other operations decrease
Solution Approach 1:
The patent implements dynamic resource allocation through the journal manager, which adjusts replication throughput based on available resources and priorities. The system dynamically prioritizes different consistency groups and adjusts replication rates, allowing resources to be allocated flexibly to meet SLOs without permanently reserving capacity. This dynamic approach optimizes resource utilization while maintaining data protection reliability.
Solution Approach 2:
The journal manager changes operational parameters such as replication priority, throughput rate, and resource allocation based on system conditions and SLO requirements. By adjusting these parameters dynamically, the system can meet data protection goals while optimizing overall resource utilization for other operations when protection requirements are satisfied.
4Reliability
If multiple consistency groups are replicated simultaneously, then comprehensive data protection is achieved, but resource contention and latency increase
Solution Approach 1:
The patent segments replication management into individual consistency group queues, with the journal manager handling each consistency group separately. This segmentation allows independent prioritization and resource allocation for each consistency group, preventing resource contention from affecting all groups uniformly. Critical consistency groups can be prioritized without impacting less critical ones, reducing overall latency while maintaining comprehensive protection.
Solution Approach 2:
The journal manager applies local quality by assigning different priorities and resource allocations to different consistency groups based on their specific SLOs and criticality. Each consistency group receives customized replication treatment, with critical groups getting higher priority and more resources, while less critical groups use available resources. This local optimization reduces resource contention latency for high-priority groups while maintaining protection for all groups.
Data Source
AI summary
Prioritization and quality of service control operations for any PiT replication operations. When replicating data from a production site to a replica site, the transmission of data is prioritized based on the perspective of a splitter and based on the perspective of an appliance, which may coordinate with multiple splitters. Quality is controlled by prioritizing which data is sent. The transmission may also perform compression when transmitting the data and may handle situations where available resources are scarce or unavailable.