Virtual disaster recovery

Whether used singly or combined, server virtualization and storage virtualization are making an impact on IT's ability to deliver disaster recovery, and to do so cost effectively.

This article can also be found in the Premium Editorial Download: Storage magazine: The benefits of virtual disaster recovery:

Storage and server virtualization make many of the most onerous disaster recovery (DR) tasks relatively easy to execute, while helping to cut overall DR costs.

If your company still lacks a viable disaster recovery (DR) strategy, it might be time to start thinking virtualization. The initial drivers behind server virtualization adoption have been improving resource utilization and lowering costs through consolidation, but next-wave adopters have realized that virtualization can also improve availability.

Virtualization turns physical devices into sets of resource pools that are independent of the physical asset they run on. With server virtualization, decoupling operating systems, applications and data from specific physical assets eliminates the economic and operational issues of infrastructure silos -- one of the key ingredients to affordable disaster recovery.

Storage virtualization takes those very same benefits and extends them from servers to the underlying storage domain, bringing IT organizations one step closer to the ideal of a virtualized IT infrastructure. By harnessing the power of virtualization, at both the server and storage level, IT organizations can become more agile in disaster recovery.

Reduce the risk

Improving disaster recovery and business continuity are perennial top-10 IT priorities because companies want to reduce the risk of losing access to systems and data. While most shops have daily data protection plans in place, fewer of them focus their efforts on true disasters, which would include any event that interrupts service at the primary production location. An event can be many different things, including power failures, fires, floods, other weather-related outages, natural disasters, pandemics or terrorism. Regardless of the cause, unplanned downtime in the data center can wreak havoc on IT's ability to maintain business operations.

The goal of a DR process is to recreate all necessary systems at a second location as quickly and reliably as possible. Unfortunately, for many firms, DR strategies are often cobbled together because there's nothing or no one mandating them, they're too costly or complex, or there's a false belief that existing backup processes are adequate for disaster recovery.

Backup technologies and processes will take you just so far when it comes to a disaster. Tier 1 data (the most critical stuff) makes up approximately 50% of an organization's total primary data. When the Enterprise Strategy Group (ESG) surveyed IT professionals responsible for data protection, 53% said their organization could tolerate one hour or less of downtime before their business suffered revenue loss or some other type of adverse business impact; nearly three-quarters (74%) fell into the less-than-three-hour range. (The results of this survey were published in the ESG research report, 2010 Data Protection Trends, April 2010.) Under the best conditions, the time it takes to acquire replacement hardware, re-install operating systems and applications, and recover data -- even from a disk-based copy -- will likely exceed a recovery time objective (RTO) of one to three hours.

Recovery from a mirror copy of a system is faster than recovering with traditional backup methods, but it's also more expensive and complex. Maintaining identical systems in two locations and synchronizing configuration settings and data copies can be a challenge. This often forces companies to prioritize or "triage" their data, providing greater protection to some tiers than others. ESG research found that tier 2 data comprises 28% of all primary data, and nearly half (47%) of IT organizations we surveyed noted three hours or less of downtime tolerance for tier 2 data. Therefore, if costs force a company to apply a different strategy or a no-protection strategy for "critical" (tier 1) vs. "important" (tier 2), some risks may be introduced.

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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 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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Using storage virtualization in a DR plan

As organizations become more comfortable with one form of virtualization, they don't have to make great intellectual or operational leaps to grasp the concept of virtualizing other data center domains. Often, IT organizations undertaking complete data center refresh initiatives position virtualization as a key part of the makeover and look to extract all possible efficiencies in one fell swoop by deploying virtualization in multiple technology areas. So it's not uncommon to see server virtualization combined with storage virtualization.

Like server virtualization, storage virtualization untethers data from dedicated devices. Storage virtualization takes multiple storage systems and treats those devices as a single, centrally managed pool of storage, enabling management from one console. It also enables data movement among different storage systems transparently, providing capacity and load balancing. In addition to lowering costs, improving resource utilization, increasing availability, simplifying upgrades and enabling scalability, the expected benefit of storage virtualization is easier and more cost-effective DR.

In a DR scenario, storage virtualization improves resource utilization, allowing organizations to do more with less capacity on hand. IT is likely to purchase and deploy far less physical storage with thin, just-in-time provisioning of multiple tiers of storage. By improving capacity utilization, organizations can reduce the amount of additional capacity purchases and more easily scale environments.

Virtualization allows storage configurations to vary between the primary and the DR site. Flexibility in configuring dissimilar systems at the production and recovery sites can introduce cost savings (by allowing existing storage systems to be reclaimed and reused), without introducing complexity. It also allows IT to mirror primary storage to more affordable solutions at a remote site, if desired.

Native data replication that integrates with the virtualized storage environment can provide improved functionality for virtual disaster recovery. Remote mirroring between heterogeneous storage systems (that is, more expensive at the primary site and less costly at the recovery site) contributes to lower costs.

Final word on virtualization

Whether used singly or combined, server virtualization and storage virtualization are making an impact on IT's ability to deliver DR, and to deliver it cost effectively. If your company has been on the sidelines, crossing its collective fingers and hoping a disaster never strikes, it might be time to investigate virtualization. And if you have virtualization in place, you should have the basic elements for an effective and cost-efficient DR environment. It's time to take the next steps.

BIO: Lauren Whitehouse is a senior analyst focusing on backup and recovery software and replication solutions at Enterprise Strategy Group, Milford, Mass.

This was first published in April 2011

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