System Administration Guide, Volume 1

Dynamic Reconfiguration and Hot-Plugging

Hot-plugging is the ability to physically add, remove, or replace system components while the system is running. Dynamic reconfiguration refers to the ability to hot-plug system components and also the general ability to move system resources--both hardware and software--around in the system or disable them in some way without physically removing them from the system.

In this Solaris release, you can hot-plug SCSI devices on SPARC and IA based platforms and PCI adapter cards on IA based systems with the cfgadm command. Features of the cfgadm command include:

The benefit of using the cfgadm command to reconfigure systems components is that you can add, remove, or replace components while the system is running. An added benefit is that the cfgadm command guides you through the steps needed to add, remove, or replace system components. See cfgadm(1M) and "SCSI Hot Plugging With the cfgadm Command" for step-by-step instructions on hot-plugging SCSI components. See "IA: PCI Hot-Plugging With the cfgadm Command" for step-by-step instructions on hot-plugging PCI adapter cards on IA based systems.


Note -

Not all SCSI and PCI controllers support hot-plugging with the cfgadm command. For a list of PCI hardware that supports hot-plugging, please refer to the Solaris 8 (Intel Platform Edition) Hardware Compatibility List.


As part of Sun's high availability strategy, this feature is expected to be used in conjunction with additional layered products, such as alternate pathing or fail-over software, which provide fault tolerance in the event of a device failure.

Without any high availability software, you can replace a failed device by manually stopping the appropriate applications, unmounting non-critical file systems, and then proceeding with the add or remove operations.

Attachment Points

The cfgadm displays information about attachment points, which are locations in the system where dynamic reconfiguration operations can occur.

An attachment point consists of:

Attachment points are represented by logical and physical attachment point IDs (ap_ids). The physical ap_id is the physical pathname of the attachment point. The logical ap_id is a user-friendly alternative for the physical ap_id. Refer to cfgadm(1M) for more information on ap_ids.

The logical ap_id for a SCSI Host Bus Adapter (HBA), or SCSI controller, is usually represented by the controller number, such as c0.

In cases where no controller number has been assigned to a SCSI HBA, then an internally-generated unique identifier is provided. An example of a unique identifier for a SCSI controller is:

fas1:scsi

The logical ap_id for a SCSI device usually looks like this:

HBA-logical-apid::device-identifier

In the example below, c0 is the logical ap_id for the SCSI HBA:

c0::dsk/c0t3d0

The device identifier is typically derived from the logical device name for the device in the /dev directory. For example, a tape device with logical device name, /dev/rmt/1, has the following logical ap_id:

c0::rmt/1

If a logical ap_id of a SCSI device cannot be derived from the logical name in the /dev directory, then an internally-generated unique identifier is provided. An example of an identifier for the tape device listed above is:

c0::st4

Refer to cfgadm_scsi(1M) for more information on SCSI ap_ids.

The cfgadm command represents all resources and dynamic reconfiguration operations in terms of a common set of states (such as configured, unconfigured) and set of operations (connect, configure, unconfigure, and so on). Refer to cfgadm(1M) for more information on these generic states and operations.

The receptacle and occupant states for the SCSI HBA attachment points are:

Receptacle State 

Description 

Occupant State 

Description 

empty

N/A to SCSI HBA 

configured

One or more devices configured on the bus 

disconnected

Bus quiesced 

unconfigured

No devices configured 

connected

Bus active 

 

 

Receptacle and occupant state mappings for SCSI device attachment points are:

Receptacle State 

Description 

Occupant State 

Description 

empty

N/A to SCSI devices 

configured

Device is configured 

disconnected

Bus quiesced 

unconfigured

Device is not configured 

connected

Bus active 

 

 

The condition of SCSI attachment points are unknown unless there is special hardware to indicate otherwise. See the instructions below on displaying SCSI component configuration information.

IA: Detaching PCI Adapter Cards

A PCI adapter card hosting non-vital system resources can be removed if the device driver supports hot-plugging. A PCI adapter card is not detachable if it is a vital system resource. For a PCI adapter card to be detachable:

For example, if a system has only one ethernet card installed in it, the ethernet card cannot be detached without losing network connection. This replacement requires additional layered software support to keep the network connection active.

IA: Attaching PCI Adapter Cards

A PCI adapter card can be added to the system as long as:

See "IA: PCI Hot-Plugging With the cfgadm Command" for step-by-step instructions on adding or removing a PCI adapter card.