Synchronous replication is a data replication method where data is written to both the primary storage location and one or more secondary locations simultaneously. The write operation is only considered complete when all copies have been successfully written and acknowledged. This approach is funda…Synchronous replication is a data replication method where data is written to both the primary storage location and one or more secondary locations simultaneously. The write operation is only considered complete when all copies have been successfully written and acknowledged. This approach is fundamental to Business Continuity planning in the CompTIA DataSys+ framework.
In synchronous replication, when an application writes data to the primary system, that same data is transmitted to the replica site in real-time. The primary system waits for confirmation from the secondary site before acknowledging the write as successful to the application. This ensures that both locations maintain identical copies of data at all times, achieving what is known as zero data loss or Recovery Point Objective (RPO) of zero.
The primary advantage of synchronous replication is data consistency. Since both sites contain the exact same information, organizations can failover to the secondary site with confidence that no transactions have been lost. This makes it ideal for mission-critical applications such as financial systems, healthcare records, and e-commerce platforms where data integrity is paramount.
However, synchronous replication does have limitations. The requirement for acknowledgment from remote sites introduces latency into write operations. This latency increases with geographic distance between sites, which typically limits synchronous replication to distances of approximately 100-300 kilometers. Beyond this range, the performance impact becomes significant.
From a Business Continuity perspective, synchronous replication supports high availability architectures and disaster recovery strategies. Organizations use this technology to maintain hot standby sites that can assume operations almost instantaneously during outages.
Cost considerations include the need for high-bandwidth, low-latency network connections between sites, as well as matching storage infrastructure at each location. Despite these costs, synchronous replication remains essential for organizations where data loss is unacceptable and Recovery Time Objectives (RTO) must be minimal.
Synchronous Replication: Complete Study Guide
What is Synchronous Replication?
Synchronous replication is a data replication method where data is written to both the primary storage location and the secondary (replica) location simultaneously. The write operation is only considered complete when both locations have confirmed the data has been successfully stored. This ensures that both copies of data are identical at all times.
Why is Synchronous Replication Important?
Synchronous replication is critical for business continuity because it provides:
• Zero Data Loss (RPO = 0): Since both copies are always identical, there is no data loss if the primary system fails • Data Consistency: Both locations always contain the same information, eliminating data discrepancies • Regulatory Compliance: Many industries require real-time data protection for sensitive information • High Availability: Enables instant failover to the replica site during outages • Transaction Integrity: Essential for financial systems and databases where every transaction must be preserved
How Synchronous Replication Works
The process follows these steps:
1. An application initiates a write request to the primary storage 2. The primary storage system sends the data to the secondary location 3. The secondary location writes the data and sends an acknowledgment back 4. Only after receiving confirmation from both locations does the primary system acknowledge the write as complete to the application 5. If either location fails to confirm, the write operation is not completed
Key Characteristics
• Distance Limitations: Works best over short distances (typically under 100 miles) due to latency concerns • Performance Impact: Write operations are slower because they must wait for remote confirmation • Network Requirements: Requires high-bandwidth, low-latency network connections • Cost: More expensive to implement than asynchronous replication
Synchronous vs. Asynchronous Replication
• Synchronous: Zero data loss, higher latency, distance-limited • Asynchronous: Potential data loss, lower latency, works over long distances
Exam Tips: Answering Questions on Synchronous Replication
1. Look for RPO clues: If a question mentions RPO of zero or no acceptable data loss, synchronous replication is likely the answer
2. Consider distance factors: Questions mentioning sites within the same metropolitan area or short distances point toward synchronous replication being feasible
3. Watch for performance trade-offs: If a scenario mentions acceptable slower write performance in exchange for data protection, think synchronous
4. Financial and healthcare scenarios: These industries often require synchronous replication for critical transaction data
5. Key terminology to recognize: Real-time replication, mirroring, zero RPO, simultaneous writes, and write acknowledgment all relate to synchronous replication
6. Eliminate wrong answers: If a question involves replication over thousands of miles or emphasizes write performance, synchronous replication is probably not the correct choice
7. Remember the confirmation requirement: The defining feature is that writes must be confirmed at both locations before completion
Common Exam Scenarios
• A company needs to ensure no transactions are lost during a disaster - Answer: Synchronous replication • Two data centers 50 miles apart need identical data - Answer: Synchronous replication is appropriate • An organization requires the fastest possible write speeds across continents - Answer: This would not use synchronous replication