Measurements, Models, Systems and Design

531 s.

RAID Organizations for Improved Reliability and Performance: A Not Entirely Unbiased Tutorial (1st revision)

RAID proposal advocated replacing large disks with arrays of PC disks, but as the capacity of small disks increased 100-fold in 1990s the production of large disks was discontinued. Storage dependability is increased via replication or erasure coding. Cloud storage providers store multiple copies of data obviating for need for further redundancy. Varitaions of RAID based on local recovery codes, partial MDS reduce recovery cost. NAND flash Solid State Disks - SSDs have low latency and high bandwidth, are more reliable, consume less power and have a lower TCO than Hard Disk Drives, which are more viable for hyperscalers.Comment: Submitted to ACM Computing Surveys. arXiv admin note: substantial text overlap with arXiv:2306.0876

Performance analysis of a dynamic query processing scheme

Traditional query optimizers produce a fixed query evaluation plan based on assumptions about data distribution and processor workloads. However, these assumptions may not hold at query execution time. In this paper, we propose a dynamic query processing scheme and we present the performance results obtained by simulation of a queueing network model of the proposed software architecture

USE OF DIGITAL TWINS TO MITIGATE COMMUNICATION FAILURES IN MICROGRIDS

This work investigates digital twin (DT) applications for electric power system (EPS) resilience. A novel DT architecture is proposed consisting of a physical twin, a virtual twin, an intelligent agent, and data communications. Requirements for the virtual twin are identified. Guidelines are provided for generating, capturing, and storing data to train the intelligent agent. The relationship between the DT development process and an existing controller hardware-in-the-loop (CHIL) process is discussed. To demonstrate the proposed DT architecture and development process, a DT for a battery energy storage system (BESS) is created based on the simulation of an industrial nanogrid. The creation and validation of the BESS DT virtual twin and intelligent agent are emphasized, including a discussion of the design choices made during the process. The use of data communication for nanogrid coordination is introduced, including the possible detrimental effects of degraded or failed communication. The BESS DT is demonstrated during nominal and off-nominal events in the nanogrid, highlighting the DT’s ability to make decisions using only local measurements rather than relying on a data communication network for coordination. The results show that the BESS DT can increase nanogrid resilience by recommending actions in response to transient events in the nanogrid, even while the data communication network has degraded or failed