Storage Management Strategies for the CIO
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By Eric Siebert
Designing and implementing a disaster recovery (DR) infrastructure is often complicated, expensive and challenging. Virtualization technologies -- for both storage and servers -- can help reduce the expense with unique approaches that differ from traditional DR methods and can provide increased flexibility and responsiveness. Server virtualization encapsulates an entire server into a single file, which makes transporting it to other locations much easier. Storage virtualization presents multiple storage devices as a single storage resource, which helps hide some of the back-end complexities of the storage devices and network. Either of these virtualization technologies will ease the implementation of a DR plan; used together, they can provide a very effective DR strategy.
For most companies, the type of DR environment they devise is typically determined by balancing the amount of money they have to spend on one-time and ongoing costs, with the required recovery time to ensure that any downtime is limited and doesn't significantly impact their business. Traditional DR scenarios usually called for maintaining a lot of physical servers at an offsite location and then using tape backups/restores or storage replication to transfer data between sites. With virtualization, there are more options for DR and the hardware requirements
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for the recovery site are greatly reduced. Even if your production data center hasn't been virtualized, you can still leverage virtualization at your remote location and convert your physical servers into virtual machines (VMs).
A variety of virtualization approaches
We'll look at some of the methods involving both server and storage virtualization that can be used as a foundation for a DR strategy. Our focus is on products and processes related to VMware Inc.'s vSphere, but many are very similar for other hypervisors like Citrix Systems Inc.'s XenServer and Microsoft Corp.'s Hyper-V. Depending on the virtualization methods used, recovery times can vary from seconds to hours to days and, accordingly, the cost and infrastructure to implement these methods will also vary. The approach you choose may be determined by whether you want a cold, warm or hot recovery site. Cold sites have no network connectivity with the main site, and limited or no hardware. Warm sites have network connectivity, and server and storage hardware, but typically lack real-time synchronization. Hot sites are almost mirror copies of critical production systems and use real-time synchronization for minimal disruption of services. The cost and recovery times differ greatly from cold to hot, but all of these types of sites can benefit greatly from using virtualization technology in their design and implementation.
This was first published in March 2010
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