The use of disk in backup environments has been accelerating for several years. We've now reached a point where most infrastructure and operations (I&O) professionals are using disk in some way, shape, or form in their backup environments. While the promise of deduplicated disk rivaling the cost of tape hasn't been truly fulfilled, most I&O professionals are supplementing their backup solutions with disk in order to benefit from faster restore times, replication capabilities, and easier management. This report explores the crowded disk library market and gives I&O pros guidance on selecting the right solutions for their organization.