In general the word replication denotes the act of copying or mirroring an object. In the same way virtual machine replication is a process of copying or reproducing a virtual machine. It’s a kind of protection of a VM to copy its current state and reproduce the same in another host or in the same host in a regular time interval.
Data replication is spread everywhere today. From the business point of view, they need to redeem their virtual machines that is running the businesses as soon as a disaster occurs. Replication plays a vital role in terms of disaster recovery which uses to recover the VM nearly without zero downtime and the ability to resume the business operations from any particular point in time.
There are two types of replication methods in VM Replication
- Synchronous Replication
- Asynchronous Replication
Synchronous Replication
Synchronous Replication is a process of copying source virtual machine’s data to the target over the network in an up to date manner. In Synchronous replication process its writing the data in both source and target machine at the same time and making sure that there is no difference between the source and target. Comparatively the synchronous replication is more expensive than the asynchronous replication as it needs high speed network to transfer the data without latency.
Let us see an example on how data are synchronized between the Source and Target in Synchronous replication method
1→ Source storage gets a data write request from its host
2→ Source storage writes the data to its storage array and immediately sends the data to the
Target storage.
3→ Target storage writes the data to its storage array and sends an acknowledgement to the source storage.
4→ Then the Source storage sends the acknowledgement to the Source host that the write request completed.
Asynchronous Replication
Asynchronous replication is a process of transferring the virtual machines data in a regular time interval unlike of maintaining both the source and target exactly the same. In asynchronous replication the source VM’s data will be copied to its replica VM in a specified time interval and not in a up to date manner. There will be some difference between the source and target in terms of its data until the configured time for replication occurs. This replication method does not need a high speed network since its having enough time to transfer data which reduces the cost.
Let us see an example on how data are synchronized between the Source and Target in Asynchronous replication method
1→ Source storage gets a data write request from its host
2→ Source storage writes the data to its storage array and sends the acknowledgement to its host.
3→ Then the Source storage sends the update to the Target storage at the specified time.
4→ Target storage writes the data to its storage array and sends the acknowledgement to the source storage.
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