About Dynamic Reconfiguration Requirements

Certain system requirements must be met in order for DR operations to succeed. These requirements are summarized below and covered in more detail in the sections that follow.

Detachability

For a PCI card to be successfully detached from a running operating environment:

• All devices on the card must use detach-safe device drivers.

• If the card controls any vital system resources, alternate paths to those resources must be available through some other card or on-board controller integrated into the system motherboard or system I/O board.

Detach-Safe Device Drivers

For a PCI card to be successfully detached from a running operating environment, each device on the card must have a detach-safe driver. A detach-safe driver enables a single instance of a driver to be closed while other instances are allowed to remain open to service similar devices used elsewhere in the system. To be considered detach-safe, a driver must be able to perform a basic Device Driver Interface/Device Kernel Interface (DDI/DKI) function called DDI_DETACH. Any driver that does not support the DDI_DETACH function is called detach-unsafe.

Sun Microsystems offers a variety of hot-pluggable PCI cards that use detach-safe device drivers. For an up-to-date list of Sun PCI cards that use detach-safe drivers, please see the Sun Fire 880 Server Product Notes or contact your local Sun sales representative.

Many third-party drivers (those purchased from vendors other than Sun Microsystems) do not support the DDI_DETACH function. Sun Microsystems suggests that you test these driver functions during the qualification and installation phases of any third-party PCI card, prior to use in a production environment.

While it is possible to detach a PCI card that has detach-unsafe drivers, it is a fairly complex procedure. To do so, you must:

1. Stop all usage of the detach-unsafe drivers on the card.

2. Stop all usage of other devices in the system that share the same detach-unsafe drivers.

3. Manually close all instances and unload all of the affected drivers.

For more information, see "How to Remove PCI Cards That Use Detach-Unsafe Drivers".

Vital System Resources

You cannot dynamically detach a PCI card that controls vital system resources unless alternate paths to those resources are available. The alternate paths must be available through a different PCI card or an on-board controller integrated into the system motherboard or system I/O board. Before detaching the card, you must switch control of the vital resources over to the alternate path (note that some multipathing software may handle this automatically). Examples of vital system resources include the system's boot disk, swap space, and primary network interface.

Some cards cannot be detached. A PCI card is not detachable if it controls a boot drive for which no alternate path is available.

If possible, the system's swap space should reside on two or more disks attached to controllers on separate boards. For example, some of the swap space might be controlled by a PCI host adapter card, while the rest could be controlled by the system's on-board controller. With this kind of configuration, a particular swap partition is not a vital system resource, because swap space is accessible through multiple controllers, and additional swap space can be dynamically configured via the swap(1M) command.

Before detaching a PCI card that controls disk swap space, you must ensure that the system's remaining memory and disk swap space will be large enough to accommodate currently running programs.