Canisters are hardware units that are subcomponents of enclosures.The system has two types of canisters: node canisters and expansion canisters.
A node canister provides host interfaces, management interfaces, and SAS interfaces to the control enclosure. A node canister has cache memory, internal drives to store software and logs, and the processing power to run the system's virtualizing and management software. A node canister also contains a battery that helps to protect the system against data loss if a power outage occurs.
An expansion canister provides the serial-attached SCSI (SAS) connectivity to the drives in an expansion enclosure. Each enclosure contains a pair of canisters to provide redundancy. An expansion canister does not contain a battery. The left canister is identified as Canister 1. The right canister is identified as Canister 2.