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Network Security for EIS and ECS Systems
Published in Barney L. Capehart, Timothy Middelkoop, Paul J. Allen, David C. Green, Handbook of Web Based Energy Information and Control Systems, 2020
If a system is critical to a company’s operations, there should be systems and storage redundancy. By having a redundancy strategy in place, low probability/ high cost events are addressed. Major systems should have identical systems on-line that will seamlessly continue operations in the event of interruption for the primary system. The most critical area for implementing redundancy is in storage media. If a primary storage media systems failure occurs without having a redundant device immediately available, it can be disastrous. A daily backup policy alone is insufficient for addressing random failures between backups. This is true for both file systems and databases. Storage media are continually decreasing in cost per unit of storage and a redundant array of inexpensive disks, or RAID, technology is practical for addressing this need. RAID is a disk system that is comprised of an array of disk drives to provide greater reliability and storage capacity and better performance at a lower cost.
Memory Organisation
Published in Pranabananda Chakraborty, Computer Organisation and Architecture, 2020
The RAID technology distributes the data involved in an I/O operation across several disks, and performs the needed I/O operations on these disks in parallel. This feature consequently can provide fast access or a higher data-transfer rate, but it depends on the arrangement of the disks employed. The performance of any of the RAID levels, however, critically depends on the request patterns of the host system and on the layout of the data. High reliability is achieved by recording redundant information; however, the redundancy employed in the RAID arrangement is different by nature from that employed in conventional disk usage. A conventional disk uses a cyclic redundancy checksum (CRC) written at the end of each record for the sake of providing reliability, whereas redundancy techniques in a RAID employ extra disks to store redundant information so that original data can be recovered even when some disks fail. Recording of, and access to redundant information, however, does not consume any such extra I/O time, because both data and redundant information are recorded/accessed in parallel. Different RAID levels, however, essentially differ in the details of the characteristics as mentioned in (2) and (3) above, and the characteristic in (3) only is not supported by RAID 0 and RAID 1.
Basic IT for Radiographers
Published in Alexander Peck, Clark’s Essential PACS, RIS and Imaging Informatics, 2017
Resilience. Some systems make use of identical copies of their hardware, which can ‘load balance’ (share loading to provide even wear) between each other during normal use, or ‘failover’ (continuing to use the non-failed components) in the event one piece fails in order to provide redundancy. For storage, a redundant array of inexpensive disks (RAID) can be utilised to give the same resilience for disks (and also performance boosts in some cases). Various ‘levels’ of RAID provide different amounts of failure tolerance, with RAID 10, e.g. providing data mirroring and striping across multiple disks allowing at minimum one disk out of the ‘array’ to fail yet the system being able to continue operating with no data loss. RAID only provides resilience and should not be considered a backup solution.
Anomaly Detection Model for Predicting Hard Disk Drive Failures
Published in Applied Artificial Intelligence, 2021
Sladjana M. Djurasevic, Uros M. Pesovic, Borislav S. Djordjevic
HDDs have been primary technology for computer data storage for several decades. Newly emerging SSDs (Solid State Drives), based on semiconductor storage, surpass HDDs in terms of response time and throughput performance. On the other hand, HDDs are dozen times cheaper per stored byte than SSDs (Appuswamy et al. 2017), and it is still the predominant data storage medium both in the enterprise and consumer market. The electromechanical design of the HDD renders it more susceptible to failures than other components of the computer system, with an average annual failure rate of HDDs in the range from 0.3 to 3%. The HDD failure generally leads to permanent data loss and typically the cost of losing data exceeds that of HDD itself. Reliability of data storage on HDD is significantly improved using RAID (Redundant Array of Independent Disks) technology which provides data retention in case one or more HDDs in RAID array had failed. RAID technology is commonly used in enterprise computer systems given its considerable cost and multiple-HDD requirement in forming a redundant array. Typical computer systems for consumer market utilize a single HDD. The prediction of HDD failure can be very useful in preventing data loss as it allows for data backup in case of imminent HDD failure warning.