In order to add additional controllers to an existing HUAWEI OceanStor system, a FC (Fibre Channel) or iSCSI (Internet Small Computer System Interface) Host Bus Adapter (HBA) is required. The HBA connects the controller to the storage devices, and it is required to add additional controllers to the system. The HBA provides the interface between the controller and the storage devices, and it allows the controller to communicate with the storage devices over the FC or iSCSI protocol. Other options such as SAS cabling, 56 Gb Infiniband module, and Smart I/O card are also important components in storage systems, but they are not directly related to adding additional controllers to an existing HUAWEI OceanStor system.

Quality of Service (QoS) is a set of technologies used to ensure that network traffic is allocated resources according to predetermined priorities. The three main working principles of QoS are I/O Priority Scheduling, I/O Performance Assurance, and I/O Flow Control. I/O Latency Burst is not one of the working principles of QoS.

A single-platter or multi-platter disk allows only one head to read and write data at a time. This means that the disk must be repositioned to read or write data to different locations, which can significantly impact the performance of the disk.

In active-standby mode, only one controller works at a time and if one controller is faulty, services are not affected. In active-active mode, both controllers are active and the service failover is more efficient than in active-standby mode.

International Organization for Standardization 2000 (ISO2000) and Information Technology Infrastructure Library (ITIL) are O&M standard systems. Institute of Electrical and Electronics Engineers (IEEE) and Storage Networking Industry Association (SNIA) are not O&M standard systems.