What does Virtual Bytes mean in Worker Processes pane in IIS7.5 Manager?

Solution 1:

This TechNet article should help to explain:

Private Bytes (KB). The current size of memory committed to a worker process, which cannot be shared with other processes. This corresponds to Virtual Memory Size in Windows Task Manager.

Virtual Bytes (KB). The current size of the virtual address space for a worker process. This does not correspond to anything in Windows Task Manager.

The memory showing in task manager is the amount of physical memory in use by the process that cannot be shared with other processes.

This MSDN page should help explain Virtual Address Space:

A virtual address does not represent the actual physical location of an object in memory; instead, the system maintains a page table for each process, which is an internal data structure used to translate virtual addresses into their corresponding physical addresses. Each time a thread references an address, the system translates the virtual address to a physical address.