Sharif Digital Repository

Data storage systems (DSSs) and their availability play a crucial role in contemporary datacenters. Despite using mechanisms such as automatic failover in datacenters, the role of human agents and consequently their destructive errors is inevitable. Due to very large number of disk drives used in exascale datacenters and their high failure rates, the disk subsystem in storage systems has become a major source of data unavailability (DU) and data loss (DL) initiated by human errors. In this paper, we investigate the effect of incorrect disk replacement service (IDRS) on the availability and reliability of DSSs. To this end, we analyze the consequences of IDRS in a disk array, and conduct... 

In this paper, we investigate the effect of incorrect disk replacement service on the availability of data storage systems. To this end, we first conduct Monte Carlo simulations to evaluate the availability of disk subsystem by considering disk failures and incorrect disk replacement service. We also propose a Markov model that corroborates the Monte Carlo simulation results. We further extend the proposed model to consider the effect of automatic disk fail-over policy. The results obtained by the proposed model show that overlooking the impact of incorrect disk replacement can result up to three orders of magnitude unavailability underestimation. Moreover, this study suggests that by... 

Emergence of Solid-State Drives (SSDs) have evolved the data storage industry where they are rapidly replacing Hard Disk Drives (HDDs) due to their superiority in performance and power. Meanwhile, SSDs have reliability issues due to bit errors, bad blocks, and bad chips. To help reliability, Redundant Array of Independent Disks (RAID) configurations, originally proposed to increase both performance and reliability of HDDs, are also applied to SSD arrays. However, the conventional reliability models of HDD RAID cannot be intactly applied to SSD arrays, as the nature of failures in SSDs are totally different from HDDs. Previous studies on the reliability of SSD arrays are based on the... 

In recent years, high availability and reliability of data storage systems (DSS) have been significantly threatened by soft errors occurring in storage controllers. Due to their specific functionality and hardware-software stack, error propagation and manifestation in DSS is quite different from general-purpose computing architectures. To the best of our knowledge, no previous study has examined the system-level effects of soft errors on the availability and reliability of DSS. In this paper, we first analyze the effects of soft errors occurring in the server processors of storage controllers on the entire storage system dependability. To this end, we implement the major functions of a... 

Low-latency data access is crucial in edge clouds serving autonomous vehicles. Storage I/O caching is a promising solution to deliver the desired storage performance at a reasonable cost in vehicular edge platforms. Current storage I/O caching methods, however, are not specialized for workload characteristics and demands of autonomous vehicles and/or do not consider the communication latency between the vehicle and the base station hosting the edge cloud node. In this work, we propose a storage mechanism for vehicular edge cloud platforms taking communication, I/O cache, and storage latencies into account. We evaluate our proposed framework using realistic storage traces of vehicular... 

The latency associated with accessing data stored on edge computing servers for vehicles encompasses both the communication between a vehicle and a server as well as a latency of a data storage system. To enable low-latency vehicular services, an efficient resource management should consider the communication as well as the storage I/O cache resource allocation along with a data access pattern and a priority of individual vehicular services. Therefore, we focus on a joint optimization of communication and storage I/O cache resource allocation for access to data of vehicular services hosted by the edge computing servers. The proposed framework determines the data placement for the services... 

All-flash storage (AFS) systems have become an essential infrastructure component to support enterprise applications, where sub-millisecond latency and very high throughput are required. Nevertheless, the price per capacity ofsolid-state drives (SSDs) is relatively high, which has encouraged system architects to adoptdata reduction techniques, mainlydeduplication andcompression, in enterprise storage solutions. To provide higher reliability and performance, SSDs are typically grouped usingredundant array of independent disk (RAID) configurations. Data reduction on top of RAID arrays, however, adds I/O overheads and also complicates the I/O patterns redirected to the underlying backend SSDs,...