In continuing our vSphere 6 ICM Series , This will be the final part. Here we will look in to vSphere Replication Overview, Architecture , and Deployment of vSphere Replication (vR).The source site provides business-critical datacenter services and the target site is an alternative facility to which you can migrate these services in case of a disaster or maintenance of the production site. Its very important to understand that vR is both a virtual machine data protection and disaster recovery solution. We can accomplish one or multiple ways mentioned below using vR :
- From a source site to a target site
- Within a single site from one cluster to another
- From multiple source sites to a shared remote target site
It is fully integrated with vCSA and vSphere Web Client. vR provides host-based, asynchronous replication of virtual machines. vR is a proprietary replication engine developed by VMware that was introduced with SRM 5, and is included with VMware vSphere Essentials Plus Kit and higher editions of VMware vSphere, VMware vSOM editions, and VMware vCloud Suite editions.
Why do we need vSphere Replication ?
Data protection and disaster recovery within the same site and across sites
Data center migration or load balancing.
Replication engine for VMware vCloud Air Disaster Recovery
Replication engine for VMware vCenter Site Recovery Manager
ARCHITECTURE DEEP DIVE
vSphere Replication is preconfigured linux based VM, which is ideally deployed using vSphere Web client . Like your vDP , vR also integrates with vCenter either windows based or vCSA. Once deployed we will have to configure the vR using Web client and we can then start configuring replication to the required VM’s that needs to be protected. vR is integrated with VMware vCenter Site Recovery Manager that automates the disaster recovery and helps reduce downtime for mission critical applications.
How does it Work?
vR is an engine that provides replication of virtual machine disk files (VMDK) and it tracks changes to VMs and ensures that blocks that differ within a specified recovery point objective (RPO) are replicated to a remote site. RPO basically is the time interval between replications. vR continuously tracks I/O destined for a VMDK file and keeps track of blocks of data that are being changed. User configures RPO for every VM or VMDK, and the VR is designed to ensure that the blocks that change are copied across the network to the remote site at a rate sufficient to keep the replica in synch with the primary VM’s protected VMDK . vR uses two different types of synchronization technologies :
1) Full Synch : In the initial sync of VM, vR reads the entire disk(VMDK’s) of both the protected and recovery site and generates a checksum for each block. It then compares the checksum mapping between the two disk files and there by creates an initial block bundle that needs to be replicated so the block checksums are in alignment. This happens on port 31031.
2) RPO Synch : These further replications is performed by an agent and vSCSI filter that reside within the kernel of an ESXi host and tracks the I/O and keeps a bitmap in memory of changed blocks and saves this information into “persistent state file” (.psf) in the home directory of the VM. The psf file contains only pointers to the changed blocks. When it is time to replicate the changes to the remote site, as dictated by the RPO set for the VMDK, a block bundle is created that are changed and this is sent to the remote site for committing to disk. This happens on port 44046.
vSphere Replication is a 64-bit virtual appliance packaged in the .ovf format. It is configured to use a dual core CPU, a 16 GB and a 2 GB hard disk, and 4 GB of RAM. Additional vSphere Replication servers require 716 MB of RAM.
Deploy the .ovf Accept EULA and Click Next, Provide the Name of the appliance and Choose the Datacenter , Choose Defaults of 4vCPU and Choose Cluster and Hosts you want to deploy this appliance .
Choose the port group you wish to use the replication traffic. This can be a separate replication port group or along with Management port group. Final step is to provide the Networking properties such as Gateway, DNS, IP Address and Subnet Mask
Set the Administrative Password.
Click Next and Check “Power on After Deployment”.
After the appliance has been deployed and powered on,We must use vSphere Web Client to access the vSphere Replication.
This completes the deployment of vR and we will see the management of replication in further Part.