Hot-Swap Units In A Stack - Dell S60 System Manual

Hot-swap Units in a Stack

You can add, remove, or swap units in an existing stack. The units in the stack and the new units can be
already powered up or they can be powered down.
All units in a stack must run the same version of the operating system. If you attempt to attach a unit with
a different version of the operating system to an existing stack, the Command Line Interface (CLI)
displays an error and the unit is not added until you install compatible software.
The order in which the units come on-line or are added to or removed from the stack can affect how the
stack identifies them and how the units identify themselves. This influences the unit numbers,
management addresses, and other elements of the configuration file.
How units are identified within the stack is determined by the selected identification algorithm. The
default algorithm has the units self-identify as Unit 1 through Unit [last] based on the order in which they
come on-line. So, when setting up a new set of switches in a stack, you should have no trouble forcing the
identification of the management unit and unit IDs by methodically supplying power to the units in your
preferred sequence.
Similarly, when you add a brand new unit to the stack, the unit will be gracefully added as Unit [last] (the
lowest unused number) with the current configuration. Attaching the unit causes each unit in the stack to
reload and the subsequent configuration file in each unit includes the awareness of the new unit.
If you have a pre-configured unit that you want to add to the stack, but you want to make sure the
configuration does not override the configuration of the stack, in order to avoid stack management
conflicts, add the unit while it is powered down.
You can use the CLI to make stack identification changes on the fly, such as renumbering units (stack-
unit unit number renumber unit number), assigning a new management unit (redundancy force-
failover stack-unit number), or removing priority or provisioning of a stack unit member (no stack-unit
unit number provision provision type). You can also use commands such as stack-unit unit number
priority value and member that override the default unit identification algorithms.
To see the current assignment of the management unit, use the show system command. To see the serial
number of the designated unit, use the show system stack-unit unit number command.
For more information about removing a unit from a stack and other stacking commands, refer to the
Stacking chapter in the FTOS Configuration Guide for the S60 System and the Stacking Commands
chapter in the FTOS Command Line Reference Guide for the S60 System.
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