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Virtualization can be a tricky technology for storage managers who need to apply traditional methods while navigating new obstacles.
Storage teams with lots of activity on the systems virtualization side face an interesting challenge: How should they deal with virtual hosts? Should they be treated as individual servers or as applications running on host systems? And what's the best way to ensure that virtual hosts don't cause a tilt in the delicate IO balance? In this article I outline key considerations for storage architects and administrators who design and implement virtualized systems.
Before we start, let's review the different kinds of virtualized systems. Virtualization can exist at the physical layer or logical layer. Physical layer virtualization lets you have system resources dynamically assigned to operating systems. Logical layer virtualization lets you have a host operating system (also known as a hypervisor) that runs on a single physical box. Logical layer virtualization comes in two flavors: a type-1 or bare-metal architecture hypervisor, and a type-2 or hosted architecture hypervisor. With physical layer virtualization, the hypervisor runs as the primary operating system on the physical box; in the latter case, it actually runs as an application or shell on another already running operating system. Operating systems running on the hypervisor are then called guest or virtual operating systems. Regardless of the type of virtualization in play, the challenges from the storage side are similar.
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