Most VMware administrators want to use VMware vSphere to replicate virtual machines. Before vSphere 5.1, administrators had to either purchase VMware Site Recovery Manager or turn to a third-party vendor for a suitable tool. VSphere 5.1 offers a slimmed down version of replication, but it's not without limitations. If you're OK with losing some capabilities, you might be able to forgo SRM.
VMware first announced the virtual machine (VM) replication feature of Site Recovery Manager (SRM) at VMworld 2011. At that time, SRM was still considered storage-array-level replication product, not VM-focused. In the Essentials Plus and higher editions of vSphere 5.1, VMware has included a "lite" version of SRM's VM replication feature. Some of the capabilities were stripped out and integrated into vCenter 5.1.
VMware defines vSphere Replication as copying a VM to another location, within or between clusters. This "makes that copy available for restoration through the VMware vCenter Server Web-based interface." So, VMware vSphere Replication differs from SRM in three significant ways:
- VSphere Replication is considered a feature of the vSphere platform rather than a subset of SRM.
- VMware says copies are made within clusters, not within data centers. However, this definition conflicts with information presented at VMworld 2012, in "vSphere Replication -- Enhancements and Best Practices," in which the term "data center migrations" was used. VMware has not responded to requests for clarification on this matter, but it could be an example of how vSphere Replication has limitations compared to SRM.
- VM restoration must be done via the Web-based interface, not the vSphere client. This is in keeping with VMware's trend away from the "fat" vSphere client in favor of the new unified Web-based client.
VMware notes administrators will use vSphere Replication for basic virtual machine replication, remote or branch office recovery, local recovery, controlling small offices or locations with one vCenter and performing data center migrations or collapse projects. Shortly after the vSphere 5.1 dot release, VMware issued a patch for issues in Replication.
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While I can envision the use-case possibilities in VMware's above list, my work and that of many VMware administrators focus on basic VM replication to ensure recovery. This is a process that we have wanted built into vSphere environments for a long time. Instead of relying on third-party licensing, training and support costs, it all comes together in a single interface of a single product from a single vendor.
Be mindful of the prerequisites to using VMware's replication offering. You must first enable vSphere Replication traffic on a VMkernel network interface card in the environment. You'll need to download, import and configure the vSphere Replication Virtual Appliance.
Bringing the virtual appliance into the infrastructure is very easy and straightforward. Once the data store, folder, resource pool, networking and vService are created, power on the appliance. In vCenter, a new context menu option, "vSphere Replication," has been added to the right-click menu of any VM. Use that option to configure the recovery point objective for that particular VM. Follow this step-by-step configuration guide from Duncan Epping for the appliance and VM options.
This technology will be especially welcome to IT shops in small and medium-sized businesses that use vSphere. Replication is streamlined with its full integration into the vCenter interface and fairly easy to install, set up and configure. VMware could take a lesson from this replication change: Make it simple and easy, and virtualization administrators will come.