Hot Plug Will Deliver Higher Availability

Dave Andrews

A new technology will let PC server administrators expand, upgrade, or replace PCI adapter cards without having to power-down the system. The new standard, PCI Hot Plug Specification, should be final by late spring, and the first hardware that supports the new PCI Hot Plug spec should be available early in the second half of this year. However, users will also have to wait for Microsoft, Novell, and SCO to upgrade their operating systems to support the new spec. These three vendors all plan to support Hot Plug with upgrades to their system software throughout the year.

The new spec is designed to make PC servers better platforms for running business-critical applications without interruption. Hot Plug PCI comes in three flavors, but all share the comm on attribute that they don't make you turn off your server when you need to replace or upgrade devices. Those flavors are: Hot Plug PCI Replacement (replace a failed or expected-to-fail device with an identical device); Hot PCI Upgrade (replace existing PCI devices and drivers with new versions); and Hot PCI Expansion (install additional I/O cards and driver software).

The burden for moving to Hot Plug is placed on the platform vendors, such as PC server and OS vendors, says Karl Walker, director of technology development at Compaq's enterprise computing group. (Compaq is a major supporter of the Hot Plug initiative and plans to release compliant hardware early in the second half of '97.) The objective is to let people use their current PCI adapters, but with new servers and OS updates to enable Hot Plug. Hot Plug will require new drivers and changes to the OS ( see the figure ). Also, compliant servers will need additions to their motherboards, such as a Hot Plug controller, and slot-specific power switches to let software remove power from a slot while the rest of the system is running. And servers will need to be built so that end users can easily get access to PCI adapter cards without disrupting the PC's operation.

PCI is not a fault-tolerant bus, so if a PCI card dies and compromises the integrity of the PCI bus or software system, the server will still need to be restarted. But Hot Plug technology does promise to alleviate server downtime due to bad PCI cards or upgrades. And this will allow for more robust PC servers to run critical applications without interruption.

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PCI Hot Plug System Overview

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