Storage virtualization is the storing-level process for forming "upstream" storage address spaces (block storage) from downstream storage address spaces (typically logical units [LUs] exported by storage subsystems). Figure 12-1 shows a virtual storage address space on the left being formed from a virtualization process acting on two other storage address spaces on the right. Figure 12-1. The Creation of Upstream Virtualized Storage StructuresThe terms downstream and upstream define I/O path directions. Something that is downstream is in the direction going away from the host. It's no surprise, then, that something that is upstream is in the direction going to the host. |