Virtual Failover in the Cloud: Challenge Abound: Page 2

Leveraging failover in the cloud is more than simply replicating to a cloud-based environment.


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MS Windows Server uses the clustering method as a proven DR technology between on-premise and remote sites. However, Windows-based clustering needs access to Active Directory. This means that IT will need to extend AD to the cloud, which requires ongoing synchronization between the network and cloud AD versions.

The more common development technique is replicating VMs and their data to the cloud so that users are transparently redirected to the cloud should the on-premise environment fail. The drawback to this architecture is resolving IP address and DNS record changes to accommodate the changed production site.

These days most service providers and vendors propagate changes for you or provide tools to do so more easily. For example, Amazon Route 53’s DNS web service automates both types of changes for developers and users, making it easier to perform failover processes within the cloud. Another way to solve the addressing issues is newer vendors who built their cloud-based DR offering from the ground up. Zadara with its Virtual Private Storage Array (VPSA) uses the public cloud to provide enterprise-level DR services on AWS and other cloud providers, and automates dynamic address changes

Why Bother? Because It’s Worth It

When you get the setup and service levels right, virtual failover to the cloud is an excellent DR option. Even with the complexity of initial setup and testing, it’s easier than leasing a remote site and physically building a second data center, not to mention the hassle and risk of keeping hardware and software essentially identical. Instead you’ll be replicating to a highly flexible and dynamically scaled environment; not a small consideration for anyone who has tried to keep two data centers in lockstep.

You’ll probably want to invest in higher bandwidth, or at the least invest in products that give you bandwidth optimization techniques – ideally you will invest in both. However, once you have made the additional investment then ongoing costs can be quite reasonable. In addition to avoiding the expense of creating and maintaining the secondary data center, you do not have to pay for staff at the secondary data center. And you can free up existing IT staff to do different high value projects.

Management may be similar to what you are used to. If you are already using VMware or Hyper-V tools to replicate to a secondary data center, you can use the same tools to replicate to the cloud. The same thing is true of third-party products since they will preserve as much as possible of familiar hypervisor console and toolsets.

Hyper-V, for example, uses Azure-centric Hyper-V Replica with Azure Site Recovery Manager to replicate and failover VMs in Virtual Machine Manager (VMM) clouds within Azure. Hyper-V Recovery Manager (HRM) automates more of this process. VMware offers Site Recovery Manager (SRM); its newer public cloud option recovery is VMware vCloud Air Disaster Recovery. Unlike SRM, Air DR provides native cloud-based DR for VMware vSphere. vCloud Air DR is built on vSphere Replication’s asynchronous replication and failover.

Not Just for DR

Drivers for cloud-based failover vary. DR is the biggest driver but data migration, test/dev and additional processes also benefit.

· VM migration. The process also works for planned processes like VM migration. A Nutanix user reported that they used Nutanix Cloud Connect as a failover site for virtualized web app migrations. Nutanix manages BUR, DR and test/dev in the public cloud using Nutanix Prism and Cloud Connect. The cloud-based Controller VM (CVM) cluster operates exactly like a remote cluster. Data moves from the on-premise cluster to the cloud accordingly.

A few days in advance of the planned migration, the user transferred all affected applications and data to the cloud by manually shutting down the VMs, waiting for the automated failover to complete, then activating the cloud cluster. They then restored the applications and data to the new environment when they were ready.

· DR tests. DR tests are traditionally awkward, unrealistic, and time-consuming, which is why companies rarely test their DR plans. With failover in the cloud, IT can easily test failover procedures and recovery times without committing to an identical remote data center. Zerto Virtual Replication is a hypervisor-based replication product that supports large-scale DR and testing in the cloud as well as automated failover and failback. Unitrends Reliable DR manages and automates application-specific testing for multi-VM applications and guarantees failover in virtualized production environments.

· Bare Metal Recovery (BMR). Virtualization in the cloud can also aid in bare metal recovery (BMR). BMR is the process of restoring an identical system in case of failure; all the way from an OS, drivers, applications and production data. Physical BMR requires an identical hardware environment for error-free restores; otherwise you’re going to see serious errors. In virtual environments, vendors like Zetta.net can recover a VM image to spin up bare metal. This makes for a much more efficient and less error-prone BMR procedure.

Given all of its attendant issues, is cloud-based failover worth researching and investing in? For many companies, yes; but not all. If you have a remote DR setup that is working for you there is no need to abandon it. This is certainly the case if your company owns multiple data centers and your have replication and DR setup between them.

However, even then IT might consider testing cloud-based DR for a pilot project in a virtualized server environment. Virtual networks are growing very fast and they throw off a lot of data. The scalability of the cloud offers real advantages in these specific environments.

Photo courtesy of Shutterstock.

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Tags: cloud computing, disaster recovery, failover

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