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Magnetic disk capacities have grown over the last decades by a factor of at least ten thousand. While the minicomputer disk drives of the late eighties could only store 600 MB of data [5], 8TB or 10TB disk drives are common today. The same is not true for disk transfer rates: they are just one hundred times higher than those of the late eighties. As a result, copying the entire contents of a disk...
We study the reliability of open and close entanglements, two simple data distribution layouts for log-structured append-only storage systems. Both techniques use equal numbers of data and parity drives and generate their parity data by computing the exclusive or (XOR) of the most recently appended data with the contents of their last parity drive. While open entanglements maintain an open chain of...
Archival data storage systems contain data that must be preserved over long periods of time but which are often unlikely to be accessed during their lifetime. The best strategy for such systems is to keep their disks powered-off unless they have to be powered up to access their contents, to reconstruct lost data, or to perform other disk maintenance tasks. Of all such tasks, reconstructing data after...
Radiation-induced Multiple Bit Upsets (MBUs) are major reliability concerns for embedded memory arrays fabricated in advanced technology nodes. Although various error correction techniques with different attributes have been developed, there has been limited efforts towards pure MBU detection. In this paper, we present stepped parity, a cost-efficient technique to detect MBUs in memory arrays. In...
ART guidelines of World Health Organization recommend a series of tests for HIV diagnostics (HIV antibody test, CD4 cell count and HIV viral load count). There are several modern technologies that are available to ensure reliable HIV diagnosis employing various principles. However, there is a need for point-of-care system that will eliminate the requirement of the patient to visit a hospital for initial...
Proteus is an open-source simulation program that can predict the risk of data loss in many disk array configurations, among which, mirrored disks, all levels of RAID arrays and various two-dimensional RAID arrays. It characterizes each array by five numbers, namely, the size n of the array, the number nf of simultaneous disk failures the array will always tolerate without data loss, and the respective...
Storage class memories (SCMs) constitute an emerging class of non-volatile storage devices that promise to be significantly faster and more reliable than magnetic disks. We propose to add one of these devices to each group of two or three RAID level arrays and store on it additional parity data. We show that the new organization can tolerate all double disk failures, between 75 and 90 percent of all...
We investigate the impact of Irrecoverable Read Errors (IREs) on Mean Time To Data Loss (MTTDL) of declustered-parity RAID 6 systems. By extending the analytic model to study the reliability of RAID 5 systems from Wu et. al. we obtain the MTTDL which mainly takes into account two types of data loss: data loss caused by three independent disk failures, and data loss due to a detected IRE during the...
Disk scrubbing periodically scans the contents of a disk array to detect the presence of irrecoverable read errors and reconstitute the contents of the lost blocks using the built-in redundancy of the disk array. We address the issue of scheduling scrubbing runs in disk arrays that can tolerate two disk failures without incurring a data loss, and propose to start an urgent scrubbing run of the whole...
We propose to increase the reliability of RAID level 5 arrays used for storing archival data. First, we identify groups of two or three identical RAID arrays. Second, we add to each group a shared parity disk containing the diagonal parities of their arrays. We show that the new organization can tolerate all double disk failures and between 75 and 89 percent of triple disk failures without incurring...
Two-dimensional RAID arrays maintain separate row and column parities for all their disks. Depending on their organization, they can tolerate between two and three concurrent disk failures without losing any data. We propose to enhance the robustness of these arrays by replacing a small fraction of these drives with storage class memory devices, and demonstrate how such a pairing is several times...
In this letter we present a reorganization method to protect against data loss when one or two disks fail in a RAID level 5. The main advantage of the proposed method is that it is robust against a second failure if a first failed disk has not been replaced yet. Our proposal is motivated by the fact that new disks have a high possibility to fail during their first year of operation and during this...
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