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 the cache memory, the 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 canister in the upper slot is identified as Canister 1. The inverted canister in the lower slot is identified as Canister 2.