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The InfoWorld SAN and NAS virtualization primer

How will storage virtualization technologies keep pace with storage requirements and maintain high service levels

By Steve Norall, InfoWorld
August 26, 2010 11:14 AM ET

InfoWorld - In just a few short years, storage virtualization, also known as block virtualization, has proven its worth in the large enterprise and traveled that well-worn path from pricey boutique solution to affordable commodity. As a standard feature in all but the most modest mid-tier storage systems, storage virtualization soothes a wide range of storage management woes for small and mid-size organizations. At the same time, dedicated solutions from top-tier vendors deliver the greatest ROI to large shops managing large SANs with intense data availability requirements.

Storage virtualization creates an abstraction layer between host and physical storage that masks the idiosyncrasies of individual storage devices. When implemented in a SAN, it provides a single management point for all block-level storage. To put it simply, storage virtualization pools physical storage from multiple, heterogeneous network storage devices and presents a set of virtual storage volumes for hosts to use.

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In addition to creating storage pools composed of physical disks from different arrays, storage virtualization provides a wide range of services, delivered in a consistent way. These stretch from basic volume management, including LUN (logical unit number) masking, concatenation, and volume grouping and striping, to thin provisioning, automatic volume expansion, automated data migration, and data protection and disaster recovery functionality, including snapshots and mirroring.

In short, virtualization solutions can be used as a central control point for enforcing storage management policies and achieving higher SLAs.

Perhaps the most important service enabled by block-level virtualization is nondisruptive data migration. For large organizations, moving data is a near-constant fact of life. As old equipment comes off lease and new gear is brought online, storage virtualization enables the migration of block-level data from one device to another without an outage. Storage administrators are free to perform routine maintenance or replace aging arrays without interfering with applications and users, and production systems keep chugging along.

Virtualization can also help you achieve better storage utilization and faster provisioning. The laborious processes for provisioning LUNs and increasing capacity are greatly simplified -- even automated -- through virtualization. When provisioning takes 30 minutes instead of six hours and capacity can be reallocated almost on the fly, you can make much more efficient use of storage hardware. Some shops have increased their storage utilization from between 25 and 50 percent to more than 75 percent using storage virtualization technology.

Four architectural approaches In a virtualized SAN fabric, there are four ways to deliver storage virtualization services: in-band appliances, out of-band appliances, a hybrid approach called split path virtualization architecture, and controller-based virtualization. Regardless of architecture, all storage virtualization solutions must do three essential things: maintain a map of virtual disks and physical storage, as well as other configuration metadata; execute commands for configuration changes and storage management tasks; and transmit data between hosts and storage.

Originally published on Click here to read the original story.

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