On Line Addition and Replacement (OLAR)

PCI Card OLAR Concepts

Introduction

The letters O, L, A and R stand for On Line Addition [and] Replacement. This, of course, refers to the ability of a PCI I/O card to be replaced (replaced and/or added) to an HP-UX computer system designed to support this feature without the need for completely shutting down, then re-booting the system or adversely affecting other system components. The system hardware uses the per-slot power control combined with operating system support to enable this feature.




	IMPORTANT: Certain "Classes" of hardware are not intended for access by users. At this time this includes V-Class and Superdome systems. HP recommends that these systems only be opened by a qualified HP Engineer. Failure to observe this requirement can invalidate any support agreement or warranty to which the owner might otherwise be entitled.

Important Terms and Concepts

The addition or replacement of an OLAR-compatible card may be done in either one of two ways:

Using the SAM utility.
Issuing command-line commands using rad.

If detailed information about the use of either of these two procedures is required, you should refer to the following document:

Configuring HP-UX For Peripherals, HP Part Number B2355-90698

This document may be ordered from HP, or you may view, download and print it from the following website: www.docs.hp.com

Table 1-1 Important Terms

Term	Meaning
OLAR	All aspects of the OLAR feature including On-line Addition (OLA) and On-line Replacement (OLR).
Power Domain	A grouping of 1 or more interface card slots that are powered on or off as a unit. (NOTE: Multi-slot power domains are not currently supported)
target card / target card slot	The interface card which will be added or replaced using OLAR, and the card slot in which it resides.
affected card / affected card slot	Interface cards and the card slots in which they reside, and which are in the same power domain as the target slot.




	IMPORTANT: In many cases, other interface cards and slots within the system are dependent upon the target card. For example: If the target card is a multiple-port card, suspending or deleting drivers for the target card slot also suspends individual drivers for the multiple hardware paths on that card).

During a card replacement operation, SAM performs a Critical Resource Analysis, which checks all ports on the target card for critical resources that would be temporarily unavailable while the card is shut down.

Planning and Preparation

For the most part SAM prevents you from performing OLAR procedures that would adversely affect other areas of the server. Refer to Configuring HP-UX For Peripherals, HP Part Number B2355-90698 for detailed information.

On-Line Addition and/or Replacement (OLAR)

Critical Resources

Replacing a card that is still operating can have extensive ramifications. Since power to the slot must be off when the old card is removed and the new card is inserted, the effects of shutting down the card's functions must be considered.This is particularly important if there is no on-line failover or backup card to pick up those functions. For example:

Which mass storage devices will be temporarily disconnected when the card is shut down?
Will a critical networking connection be lost?

A critical resource is one that would cause a system crash or prevent the operation from successfully completing if the resource were temporarily suspended or disconnected. For example, if the SCSI adapter to be replaced connects to the unmirrored root disk or swap space, the system will crash when the card is shut down.During an OLAR procedure, it is essential to check the targeted card for critical resources, as well as the effects of existing disk mirrors and other situations where a card's functions can be taken over by another card that will not be affected.

Fortunately SAM performs a thorough critical resource analysis automatically, and presents options to you based on it's findings. If you determine that critical resources will be affected by the procedure, you could replace the card when the server is off-line, or if you must take action immediately, you can use rad to attempt an on-line addition of a backup card and deletion of the target card.

For those wishing to use OLAR, your system may need to update its firmware. For additional details, please refer to the Readme Before Installing or Updating to HP-UX 11i document provided with you HP product.

Card Compatibility

On-Line Addition (OLA)

When on-line adding an interface card, the first issue that must be resolved is whether the new card is compatible with the system. Each OLAR-capable PCI slot provides a set amount of power. The replacement card cannot require more power than is available.

The card must also operate at the slot's bus frequency. A PCI card must run at any frequency lower than its maximum capability, but a card that could only operate at 33 MHz would not work on a bus running at 66 MHz. rad provides information about the bus frequency and power available at a slot, as well as other slot-related data.

On-Line Replacement

When on-line replacing an interface card, the replacement card must be identical to the card being replaced or at least able to operate using the same driver as the replaced card. This is referred to as like-for-like replacement and should be adhered to because using a similar but not identical card may cause unpredictable results. For example, a newer version of the target card which is identical in terms of hardware may contain an updated firmware version that could potentially conflict with the current driver.

The PCI specification allows a single physical card to contain more than one port. A single-port SCSI bus adapter can not be replaced by a dual-port adapter, even if the additional port(s) on the card was identical to the original SCSI bus adapter.

When the replacement card is added to the system, the appropriate driver for that card must be configured in the kernel before beginning the operation. SAM ensures the correct driver is present. (In most cases, the replacement card will be the same type as a card already in the system, and this requirement will be automatically met.) If you have any question about the driver's presence, or if you are not certain that the replacement card is identical to the existing card, you can use ioscan together with rad to investigate.

If the necessary driver is not present and the driver is a dynamically loadable kernel module (DLKM), you can load it manually. Refer to the section Dynamically Loadable Kernel Modules in Chapter 2 of the document: Configuring HP-UX for Peripherals, HP Part Number B2355-90698, for more information.
If the driver is static and not configured in the kernel, then the card cannot be On-line Added. The card could be physically inserted on-line, but no driver would claim it.