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Benefits of server virtualization for DR

Virtualization has become a major catalyst for change in x86 environments because it provides new opportunities for more cost-effective DR. When looking at the reasons behind server virtualization initiatives coming in the next 12 to 18 months, ESG research found that making use of virtual machine replication to facilitate disaster recovery ranked second behind consolidating more physical servers onto virtualization platforms. (See the ESG research report, 2011 IT Spending Intentions, published in January 2011, for details of the survey results.)

Because server virtualization abstracts from the physical hardware layer, it eliminates the need for identical hardware configurations at production and recovery data centers, which provides several benefits. And since virtualization is often a catalyst to refresh the underlying infrastructure, there's usually retired hardware on hand. For some organizations that might not have been able to secure the CapEx to outfit a DR configuration, there may be an opportunity to take advantage of the "hand-me-down" hardware. Also, by consolidating multiple applications on a single physical server at the recovery data center, the amount of physical recovery infrastructure required is reduced. This, in turn, minimizes expensive raised floor space costs, as well as additional power and cooling requirements.

Leveraging the encapsulation and

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portability features of virtual servers aids in DR enablement. Encapsulating the virtual machine into a single file enables mobility and allows multiple copies of the virtual machine to be created and more easily transferred within and between sites for business resilience and DR purposes -- a dramatic improvement over backing up data to portable media such as tape and rotating media at a cold standby site. In addition, protecting virtual machine images and capturing the system state of the virtual machine are new concepts that weren't available in the physical world. In a recovery situation, there's no need to reassemble the operating system, re-set configuration settings and restore data. Activating a virtual machine image is a lot faster than starting from a bare-metal recovery.

Flexibility is another difference. Virtualization eliminates the aforementioned need for a one-to-one physical mirror of a system for disaster recovery. IT has the choice of establishing physical-to-virtual (P2V) and virtual-to-virtual (V2V) failover configurations -- locally and/or remotely -- to enable rapid recovery without incurring the additional expense of purchasing and maintaining identical hardware. Virtualization also offers flexibility in configuring active-active scenarios (for example, a remote or branch office acts as the recovery site for the production site and vice versa) or active-passive (e.g., a corporate-owned or third-party hosting site acts as the recovery site, remaining dormant until needed).

Finally, virtualization delivers flexibility in the form of DR testing. To fully test a disaster recovery plan requires disabling the primary data center and attempting to fail over to the secondary. A virtualized infrastructure makes it significantly easier to conduct frequent nondisruptive tests to ensure the DR process is correct and the organization's staff is practiced in executing it consistently and correctly, including during peak hours of operation.

With server virtualization, a greater degree of DR agility can be achieved. IT's ability to respond to service interruptions can be greatly improved, especially with new automation techniques, such as those available for VMware virtualization technology (see "Automating DR in VMware environments," below) and Microsoft System Center Virtual Machine Manager, which offers tools to determine which applications and services to restore in which order. Recovery can be quicker and the skills required by operations staff to recover virtualized applications are less stringent.

Automating DR in VMware environments

VMware Inc. introduced a VMware vCenter management service in 2008 to automate, document and facilitate disaster recovery (DR) processes. VMware vCenter Site Recovery Manager (SRM) turns manual recovery runbooks into automated recovery plans, providing centralized management of recovery processes via VMware vCenter. SRM accelerates recovery, improves reliability and streamlines management over manual DR processes.

VMware SRM automates the setup, testing and actual failover courses of action. With SRM, organizations can automate and manage failover between active-passive sites -- production data center (protection site) and disaster recovery (recovery site) location -- or active-active sites, two sites that have active workloads and serve as recovery sites for each other.

SRM integrates with third-party storage- and network-based replication solutions via a storage replicator adapter (SRA) installed at both the primary and recovery sites. The SRA facilitates discovery of arrays and replicated LUNs, and initiates test and failover, making it much easier to ensure that the storage replication and virtual machine configurations are established properly. Datastores are replicated between sites via preconfigured array- or network-based replication.

SRM doesn't actually perform data protection or data recovery, at least not yet. VMware pre-announced its forthcoming IP-based replication feature in SRM. It will be able to protect dissimilar arrays in local and remote locations, provide virtual machine-level granularity and support local (DAS or internal) storage. This opens up lots of possibilities for companies that don't have a SAN or don't want to be limited to a peered storage replication solution. Even those who have taken advantage of SRM with SAN-based replication between like storage arrays at production and recovery sites can extend recovery strategies to other tiers of workloads with an asynchronous solution.

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This was first published in April 2011

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