“All problems in computer science can be solved by another level of indirection — except for the problem of too many layers of indirection.” – David Wheeler

This principle is particularly applicable when you think of it in the context of virtualization and storage. Virtualization introduces a new layer of abstraction — the VM — that provides unprecedented benefits, including consolidation, flexibility, and high availability. But other critical parts of the infrastructure still use their own layers of indirection. Existing networked storage is designed for every imaginable type of workload. It presents abstractions such as LUNS or volumes, RAID groups, and queues to create and present logical disks to applications. In the previous all-physical world, these abstractions were effective and mapped directly to the workloads. These legacy storage systems were designed before virtualization was even a consideration, and adapted to virtualization via the typical computer industry approach: Introduce another layer of abstraction to mask the complexity of meshing these two layers together.