Developing a Storage Driver

This example uses the reference model developed in Chapter 8 and applies the concepts discussed in Chapters 9, 10, and 11 to illustrate the process flow of a storage driver. It shows the steps involved in initializing the application, how the application creates and connects its queue pairs, and how the application uses the QPs to perform I/O transactions (i.e., perform disk reads and writes).

The example makes the following assumptions:

• The subnet consists of a subnet manager, a host, and an I/O unit with a device management agent.

• The I/O controller protocol uses a service name of Storage.xyz.

• The host and I/O unit share a partition where the host is not a limited member.

• The host employs the Channel Access Layer defined in Chapter 8 and Chapter 9.

Process Flow

The four main modules are:

• Initialization This starts at the point where the I/O Resource Manager (IORM) finds the storage controller on an I/O unit and loads the I/O driver.

• Assignment The IORM identifies the I/O controller to the I/O driver, and the I/O driver uses management functions to derive pertinent information about the I/O controller and establish connections with it. This phase repeats each time the IORM assigns a new I/O controller to the I/O driver.

• Input...