Access to data is vital for smooth business operations. However, the threat of hardware failures, cyberattacks and natural disasters often block or corrupt data. Businesses and IT professionals then end up working round the clock recreating and recovering lost data.
To safeguard data and ensure reliable data access, adopting data replication is the way to go.
What Is Data Replication?
Data replication is the process of making multiple copies of the same data and storing them in different locations, such as two on-premises software instances or appliances, between appliances placed in separate locations, or two completely geo-physically separated appliances via cloud-based services.
What is the purpose of data replication?
Data replication enables consistent duplication of transactions and maintains selected parts of an application (for example, a database) at different locations, keeping the updates in sync with the primary data. It helps businesses improve data availability and accessibility, which yields more resilient and reliable systems.
Advantages of Data Replication [H2]
While data replication is often a component of a disaster recovery (DR) strategy, that is far from its only use case. When done right, data replication offers immense benefits to businesses, end users and IT professionals alike.
Improve data availability
Data replication enhances the resilience and reliability of systems by storing data at multiple sites across the network. That means, in case of a technical glitch due to malware, software errors, hardware failure or other disruption, data access can still occur from a different site. It’s a live saver for organizations that operate in several locations since it guarantees 24/7/365 access to data across all geographies.
Speedier access to data
Folks may experience some latency while accessing data from one country to another. Storing replicas on local servers provides users with quicker data access and query execution times. Employees across multiple branches of an organization can access data from the branch office or home with ease.
Upgrade server performance
Data replication lightens the data load on the primary server by dispersing the database among other sites in a distributed system, leading to improved network performance. IT professionals reduce processing cycles on the primary server for write operations.
Support disaster recovery (DR)
Businesses are often susceptible to data loss, deletion or corruption due to data breaches or hardware malfunction. Data replication maintains backups of the primary data on a secondary appliance (hot copies), which are available immediately for recovery and failover. For instance, data replication to removable media, such as disk, enables IT to create an air gap. These off-site, air-gapped copies in a tested DR environment remain one of the best defenses against malware and ransomware attacks.
How Does Data Replication Work?
Replication involves writing or copying data to different locations. Copies are either created on-demand, transferred in bulk or batches according to a schedule, or replicated in real time as data is written, changed or deleted in the master source. Successful data replication is made up of several components, types, techniques and schemes.
To understand how data replication works, let’s start with the three components:
Publisher: It’s where the source of the data resides and objects are created for replication articles. These articles are grouped and published in single or multiple publications to replicate data as a unit.
Distributor: The replicated databases from the publisher are held here, which are sent over to the subscriber eventually.
***Subscriber:***The recipient of the replicated data, which can receive data from multiple publishers at the same time.
Synchronous replication vs. asynchronous replication
Data replication solutions available in the market follow either synchronous replication or asynchronous replication.
Synchronous replication
Synchronous replication solutions typically write data to the primary storage and the replica (target) simultaneously. In this way, the primary copy and replica remain identical in near real time. However, it puts a big dent in your IT budget due to its hefty price tag and may cause latency that slows the primary application (source). Synchronous replication is used frequently for high-end transactional applications that require instant failover if the primary fails.
Asynchronous replication
When performing asynchronous replication, data is written to the primary source first, then depending on settings and implementation, the data is replicated to the target medium in predetermined intervals. There’s more bandwidth for production as the replication can be scheduled during times of low network utilization. This technique is supported by most network-based replication products.
Types of data replication
There are three traditional data replication methods, which are governed by data requirements, resources and restrictions.
Transactional replication
The data replication software makes full initial copies (in real time) of data from origin to destination, i.e., publisher to the receiving database (subscriber), in the same chronology as they occur with the publisher. Transactional replication does not allow an entire copy of all data changes. Instead, it replicates each change. Incremental changes to data in this manner improve performance and decrease latency.
Snapshot replication
Snapshot replication takes a snapshot of the data on one server and moves that data to another server (or another database on the same server) in a single transaction. Data is replicated exactly as it appears at any given time. It does not update every transaction between the servers nor the order of data change. Snapshot replication works well when data doesn’t change frequently or if significant changes occur over a short period.
Merge replication
Merge replication combines data from multiple sources into a single central database. The initial synchronization from the publisher is a snapshot replication. However, it allows data changes to occur at both the publisher and subscriber levels. The modified data is sent to a merge agent (installed on all servers) and uses conflict resolution algorithms to update and distribute the data. This type of replication is commonly found in server-to-client environments, allowing users to make changes offline before synchronizing data with the server.
Database replication techniques
Although techniques for replicating data may vary across organizations, these are the most common replication techniques:
Full-table replication
Full-table replication means that the entire data set is replicated in every transaction — including new, updated and existing data. This replication technique effectively enables the recovery of hard-deleted data and databases that do not possess replication keys.
Key-based incremental replication
Key-based incremental captures data changed since the last update. Keys are elements that exist within databases to initiate data replication. This technique works for databases that focus on the new changes rather than historical values and store data records on unique elements (keys).
Log-based incremental replication
Log-based replication is a method in which modifications are recorded (known as a log file or changelog) to make necessary changes. This type of data replication technique is available only for MySQL, PostgreSQL and MongoDB backend databases.
Database replication schemes
The following replication schemes are used for database replication:
Full replication
Full replication means the complete database is replicated at every node of the distributed system. This scheme maximizes data redundancy, increases global performance and data availability.
Partial replication
Partial replication occurs when certain parts of a database are replicated based on the criticality of data at each location. As a result, the number of replicas can range from one to the exact number of nodes in the distributed system.
No replication
No replication is when only one fragment exists on each node of the distributed system. This replication scheme is the fastest to perform and helps in achieving effortless data synchronization.
## Data Replication Made Easy With Unitrends
For DR recovery efforts to be successful, data replication needs to be on point.
Data replication with Unitrends is a guaranteed way to ensure 100% confidence in your data recovery.
Here are some ways Unitrends can help organizations and IT folks enable successful data replication:
Long-term retention
Unitrends can replicate copies of data and set them for a variety of targets for long-term retention to meet industry, legal or compliance requirements. The Unitrends Cloud is one such target and is a purpose-built cloud infrastructure designed to offer inexpensive, automated data protection without the complexity of public clouds, with predictable, straightforward costs and no charges for egress or ingress.
Off-site backup copy (redundancy)
Unitrends can replicate data to off-site targets (cloud or secondary appliance) and removable media, which is taken off-site to create an air gap. Redundant backup copies residing on another Unitrends appliance are stored in a “Hot” state and are immediately available for recovery. Backup copies residing on external media (such as HDDs) are considered “Cold” and the data must be imported to a Unitrends appliance before restoration.
Disaster recovery
Redundant backup copies residing on another Unitrends appliance are stored in a Hot state and are immediately available for recovery. Data Copy Access jobs can be configured to orchestrate the recovery of multiple machines to a designated target in a pre-defined boot order with only a few clicks. By replicating backups to the Unitrends Cloud, customers can leverage Unitrends Disaster Recovery as a Service. This white-glove service reduces the cost and complexity of protecting critical workloads by delivering rapid spin-up of systems and applications in the Unitrends Cloud. The Unitrends Cloud and DR experts take responsibility for the entire DR process, right from installation to failover and recovery of service, and failback to your operational data center.