Sun Enterprise 6x00, 5x00, 4x00, and 3x00 Systems Dynamic Reconfiguration User's Guide

Definitions

Attachment Point

Attachment point: a collective term for a board and its card cage slot.

DR can display the status of the slot, the board, and the attachment point. For DR purposes, a board also includes the devices connected to it, so the DR term occupant is used to refer to the combination of board and attached devices.

A slot (also called a receptacle) may have the ability to electrically isolate the occupant from the host machine. That is, DR software can put a single slot into low-power mode.

Receptacles can be named according to slot numbers or can be anonymous (for example, a SCSI chain). To obtain a list of all available logical attachment points, use the -l option with the cfgadm command.

An occupant I/O board includes any external storage devices connected by interface cables.

There are two types of system names for attachment points:

A physical attachment point describes the software driver and location of the card cage slot. An example of a physical attachment point name is:
```
/devices/central@1f,0/fhc@0,f8800000/clock-board@0,900000:sysctrl,slot0
```

A logical attachment point is an abbreviated name created by the system to refer to the physical attachment point:
```
sysctrl0:slot0
```

Detachability

A board is not detachable if it has a critical resource (such as a boot drive) connected to it. Similarly, if a system has only one CPU board, the CPU board cannot be detached.

For a device to be detachable:

The device driver must support DDI_DETACH
Critical resources must be accessible through an alternate pathway

If there is no alternate pathway for an I/O board, you can:

Put the second disk chain on a separate I/O board. The secondary I/O board can be detached (with a loss of access to the secondary disk chain).

Add a second path to the device through a second I/O board. The I/O board can be detached (using Alternate Pathing software to switch access through the alternate board) without losing access to the secondary disk chain.

Conditions and States

State: the operational status of either a receptacle (slot) or an occupant (board).

Condition: the operational status of an attachment point.

The cfgadm program can display 10 types of states and conditions. See Table 2-1.

Note -

For a receptacle procedure to be valid, the receptacle must transition in sequence through all three states (empty, disconnected, connected) or in the reverse sequence (connected, disconnected, empty).

Connection and Configuration

There are four main types of DR operations:

Connection: in this operation, the slot provides power to the board and begins monitoring the board temperature.

Configuration: the operating system assigns functional roles to a board and loads device drivers for the board and for devices attached to the board.

Unconfiguration: the system detaches a board logically from the operating system and takes the associated device drivers offline. Environmental monitoring continues, but any devices on the board are not available for system use.

Disconnection: the system stops monitoring the board and power to the slot is turned off.

If a system board is in use, before powering it off and removing it, stop its use and unconfigure it. After a new or upgraded system board is inserted and powered on, connect its attachment point and configure it for use by the operating system.

cfgadm can connect and configure (or unconfigure and disconnect) in a single command, but if necessary, each operation (connection, configuration, unconfiguration, or disconnection) can be performed separately.

Hot-plug Hardware

Hot-plug: hot-plug boards and modules have special connectors which supply electrical power to the board or module before the data pins make contact. Boards and devices which do not have hot-plug connectors cannot be inserted or removed while the system is running.

I/O boards and CPU/memory boards used in Enterprise x000 and x500 systems are hot-plug devices. Some devices, such as the clock board and peripheral power supply (PPS), are not hot-plug modules and cannot be removed while the system is running.

Quiescence

Quiescence: during a DR unconfigure/disconnect operation on a system board with non-pageable Open Boot PROM (OBP) or kernel memory, the operating system is briefly paused, which is known as operating system quiescence. All operating system and device activity on the backplane must cease for a few seconds during a critical phase of the operation.

Before it can achieve quiescence, the operating system must temporarily suspend all processes, processors, and device activities. If the operating system cannot achieve quiescence, it displays the reasons, which may include the following:

A user thread did not suspend

Real-time processes are running

A device exists that cannot be paused by the operating system

The conditions that cause processes to fail to suspend are generally temporary. Examine the reasons for the failure. If the operating system encountered a transient condition--a failure to suspend a process--you can try the operation again.

Suspend-Safe and Suspend-Unsafe Devices

suspend-safe: a suspend-safe device is one that does not access memory or interrupt the system while the operating system is in quiescence. A driver is suspend-safe if it supports operating system quiescence (suspend/resume). It also guarantees that when a suspend request is successfully completed, the device that the driver manages will not attempt to access memory, even if the device is open when the suspend request is made.

suspend-unsafe: a suspend-unsafe device is one that allows a memory access or a system interruption while the operating system is in quiescence.

Suspend-safe drivers provide the ability to:

Stop user threads
Execute the DDI_SUSPEND call in each device driver
Stop the clock
Stop the CPUs

The operating system refuses a quiescence request if a suspend-unsafe device is open. To manually suspend the device, you may have to close the device by killing the processes that have it open, asking users not to use the device, or disconnecting the cables. For example, if a device that allows asynchronous unsolicited input is open, you can disconnect its cables prior to activating operating system quiescence and reconnect them after the operating system resumes. This action prevents traffic from arriving at the device and, thus, the device has no reason to access the backplane.

Testing for Suspend-Safe Drivers

The quiesce-test option tests for suspendable drivers.

# cfgadm -x quiesce-test sysctrl#:slot#

Tape Devices

The sequential nature of tape devices prevents them from being reliably suspended in the middle of an operation, and then resumed. Therefore, all tape drivers are suspend-unsafe. Before executing a DR operation that activates operating system quiescence, make sure all tape devices are closed or not in use.