This book is a complete presentation of the content of the PCI Hot-Plug Specification. Each of the requirements of the PCI Hot Plug specification is presented. Additional background information is provided that explains why the specification was written as it was, or possible consequences of non-compliance.
Over the past decade a new class of business machinery has emerged the standards-based server. Leveraging the economies of scale of the personal computer industry, this class of machine has advanced far beyond its original personal roots. Today s servers often use multiple microprocessors, each with performance several orders of magnitude greater than their ancestors of a decade ago. Storage systems once measured in the tens of megabytes can now be measured in terabytes.
With the growth of robust operating systems such as Novell IntranetWare, Microsoft Windows NT, and x86 versions of Unix from Santa Cruz Operation (SCO), the standards-based server has become an essential piece of business infrastructure. Anxious to take advantage of the dramatic reduction in the price/performance ratio of such systems, businesses have enthusiastically transferred to standards-based servers data and applications essential to their day-to-day operation.
Essential business applications require much more than faster hardware, more storage, and different operating systems. As businesses depend more upon their servers, reliability and manageability has become more important. Company-wide local-area networks and email systems, first implemented for convenience, have become mission-critical applications. Loss of the network for even short periods of time can have enormous impact on a company s operation. Furthermore, the need to simplify system management, and the availability of higher performance server, has enabled consolidation of multiple smaller servers into fewer more powerful ones. This trend multiplies the need for constant availability as each downtime event affects more and more people in bigger and bigger ways.
Server hardware and software manufacturers have responded to the demand for more reliable systems by introducing hardware redundancy and expanded system management tools. Redundant arrays of independent disks (RAID) storage systems protect critical data in the least reliable subsystem, the mechanical operation of the disk drives. RAID systems commonly include hot-plug drives that enable the user to replace the failed component or expand storage capacity without interrupting the overall operation of the server. Error-correcting memory subsystems protect system operation against random memory errors. Redundant power supplies, backup processor cards, redundant network interface cards (NICs), and even schemes for one system to fail and transfer all operation to a different system have all been introduced to reduce the occurrence or length of downtime events.
The next step on the road to increased availability of servers is in the I/O subsystem. Since its introduction in 1992, the PCI local bus has become the most widely used I/O bus in standards-based server systems. Compaq Computer Corporation recognized the need for defining a standard way to remove and install standard PCI adapter cards without powering-off the server. In June 1996 Compaq approached the Steering Committee of the PCI Special Interest Group to form a workgroup to develop such a standard. The workgroup was immediately formed with Compaq as the chair. The amazing unity among the workgroup member companies, and the speed at which the first draft of the specification was published, testify to the recognition in the industry of the need for PCI hot-plug capabilities. Draft 0.9 of the PCI Hot-Plug Specification was made public in March of 1997, nine months after the Steering Committee chartered the workgroup. At the time of this writing, the final version of the specification is in the final release process. Formal release of the specification by the PCI Steering Committee should occur in October of 1997.
This book is first of all a complete presentation of the content of the PCI Hot-Plug Specification. Each of the requirements of the specification is presented. Where appropriate, additional background information is presented that explains why the specification was written as it was, or possible consequences of non-compliance. This book is not intended to replace the specification. The ultimate authority on PCI hot-plug operations remains the official specification. However, reading this book prior to or concurrently with the specification should improve the reader s understanding of the requirements of the specification. The reader is assumed to be familiar with the PCI Local Bus Specification, Revision 2.1.
In addition to presenting the content of the specification, this book also includes application information that is beyond the scope of the specification. Chapter 7 discusses the hardware implemented in Compaq s first product designed to this specification, the ProLiant 6500, as an example of platform hardware. Chapter 8 discusses how the specification is addressed in the first products from Novell, Microsoft, and SCO.
