OLA/R Overview and Concepts

Planning and Preparation

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.

•During the replacement process, the original driver instance runs in a suspended state. I/O to the card is either queued or failed while the card is suspended. When the replacement card is brought on-line, the driver instance resumes normal operation. The driver instance must be capable of resuming and controlling the replacement card.

•If the necessary driver is not present and the driver is a dynamically loadable kernel module (DLKM), you can load it manually.

•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.

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 OLA/R 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 SMH 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

Chapter 4

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