Database Replication:
Typically a database server maintains the master copy of the database and additional database server maintains slave copies of the database. Database writes are sent to the master database server and are then replicated by the slave database servers. Database reads are divided among all of the database servers, which results in a large performance advantage due to load sharing. In addition, database replication can also improve availability because the slave database servers can be configured to take over the master role if the master database server becomes unavailable.
Host based Replication:
Host-based replication is often used in smaller environments or on a departmental basis. A host-based solution can be deployed at a lesser cost of a high-end, storage-based implementation. Host to Host Replication is also referred to as processor-based replication. In this type, the replication process runs on the source and target systems. Due to this, it is possible that the replication process might introduce contention with other applications running on the source system. This is accomplished through an agent that runs on each system to track data changes and replicate them to the remote host over an IP connection. This type of replication can be performed at the OS level or at the application level. Host to Host is the most commonly implemented replication because it is a software-only solution.
Disk to Disk (D2D) Replication
D2D replication runs on an external storage such as SAN or NAS. D2D replication utilizes resources on the external storage hardware and is transparent to the host. Because the replication process is run on the external storage, a dedicated target host is not required. This entails the addition of an appliance into the SAN architecture that has mirrored access to the storage links. This appliance replicates write activity to the remote appliance and storage array. This approach can be utilized to replicate dissimilar storage arrays or reduce cost by allowing for the implementation of lower-cost storage at the target site.
Advantages of using Replication: |