1*8b38b177SShawn McCarney# Multiple Chassis 2*8b38b177SShawn McCarney 3*8b38b177SShawn McCarney## Overview 4*8b38b177SShawn McCarney 5*8b38b177SShawn McCarneyA BMC-based system can contain one or more chassis. A chassis is typically a 6*8b38b177SShawn McCarneyphysical enclosure that contains system components such as CPUs, fans, power 7*8b38b177SShawn McCarneysupplies, and PCIe cards. 8*8b38b177SShawn McCarney 9*8b38b177SShawn McCarneyA chassis can be stand-alone, such as a tower or desktop. A chassis can also be 10*8b38b177SShawn McCarneydesigned to be mounted in an equipment rack. 11*8b38b177SShawn McCarney 12*8b38b177SShawn McCarneyFor the `phosphor-regulators` application, the term "single chassis system" 13*8b38b177SShawn McCarneymeans the system type has a maximum configuration of one chassis. If the system 14*8b38b177SShawn McCarneytype has a maximum configuration of multiple chassis, then it is considered a 15*8b38b177SShawn McCarney"multiple chassis system" even if the current system only contains one chassis. 16*8b38b177SShawn McCarney 17*8b38b177SShawn McCarney`phosphor-regulators` only supports powering on and off the entire system. It 18*8b38b177SShawn McCarneydoes not support powering on/off individual chassis independent of the rest of 19*8b38b177SShawn McCarneythe system. 20*8b38b177SShawn McCarney 21*8b38b177SShawn McCarney## Defining the chassis in a system 22*8b38b177SShawn McCarney 23*8b38b177SShawn McCarneyThe [JSON configuration file](config_file/README.md) contains an array of one or 24*8b38b177SShawn McCarneymore [chassis](config_file/chassis.md) objects. Each chassis object corresponds 25*8b38b177SShawn McCarneyto a physical chassis in the system. 26*8b38b177SShawn McCarney 27*8b38b177SShawn McCarney## Differences between single and multiple chassis systems 28*8b38b177SShawn McCarney 29*8b38b177SShawn McCarney### System and chassis power state 30*8b38b177SShawn McCarney 31*8b38b177SShawn McCarneyIn a single chassis system, the system and chassis power state are identical. 32*8b38b177SShawn McCarneyBoth are either on or off. 33*8b38b177SShawn McCarney 34*8b38b177SShawn McCarneyIn a multiple chassis system, each chassis has its own power state. Even if the 35*8b38b177SShawn McCarneysystem is on, an individual chassis may be off. This can occur if that chassis 36*8b38b177SShawn McCarneydoes not have input power or has a critical hardware problem. 37*8b38b177SShawn McCarney 38*8b38b177SShawn McCarneySee [Chassis Status](../phosphor-power-sequencer/docs/chassis_status.md) for 39*8b38b177SShawn McCarneymore information. 40*8b38b177SShawn McCarney 41*8b38b177SShawn McCarney### Configuration 42*8b38b177SShawn McCarney 43*8b38b177SShawn McCarneyIn a single chassis system, regulator configuration is always performed on the 44*8b38b177SShawn McCarneychassis. 45*8b38b177SShawn McCarney 46*8b38b177SShawn McCarneyIn a multiple chassis system, regulator configuration will only be performed on 47*8b38b177SShawn McCarneychassis with the proper status. For example, a chassis that is missing or has no 48*8b38b177SShawn McCarneyinput power cannot be configured. 49*8b38b177SShawn McCarney 50*8b38b177SShawn McCarneySee [Regulator Configuration](configuration.md) for more information. 51*8b38b177SShawn McCarney 52*8b38b177SShawn McCarney### Monitoring 53*8b38b177SShawn McCarney 54*8b38b177SShawn McCarneyIn a single chassis system, regulator monitoring is always performed on the 55*8b38b177SShawn McCarneychassis. 56*8b38b177SShawn McCarney 57*8b38b177SShawn McCarneyIn a multiple chassis system, regulator monitoring will only be performed on 58*8b38b177SShawn McCarneychassis with the proper status. For example, a chassis that is missing or has no 59*8b38b177SShawn McCarneyinput power cannot be monitored. 60*8b38b177SShawn McCarney 61*8b38b177SShawn McCarneySee [Regulator Monitoring](monitoring.md) for more information. 62