Sharif Digital Repository

Data reduction technologies have proven their effectiveness to decrease the ever-growing demands on storage system capacities, but also introduce new complexity in the system I/O stack that can easily invalidate well-known best practices. In this paper, we conduct an extensive set of experiments on an enterprise all-flash storage (AFS) system equipped with an open-source data reduction module, i.e., RedHat VDO, and reveal novel observations on the performance gap between the state-of-the-art and the optimal AFS stack with integrated data reduction. We then offer cross-layer optimizations to enhance the performance of AFS, which range from deriving new optimal hardware RAID configurations up... 

Data reduction technologies have proven their effectiveness to decrease the ever-growing demands on storage system capacities, but also introduce new complexity in the system I/O stack that can easily invalidate well-known best practices. In this paper, we conduct an extensive set of experiments on an enterprise all-flash storage (AFS) system equipped with an open-source data reduction module, i.e., RedHat VDO, and reveal novel observations on the performance gap between the state-of-the-art and the optimal AFS stack with integrated data reduction. We then offer cross-layer optimizations to enhance the performance of AFS, which range from deriving new optimal hardware RAID configurations up... 

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... 

In this paper, utilizing the benefits of network coding, we introduce a scheme for uncoordinated dynamic distributed storage systems in which nodes can randomly join and leave the storage network. The proposed scheme can reduce the bandwidth requirement of the storage network  

The growing utilization rate of electric vehicles (EVs) because of their advantages, like environmental pollutant reduction, may bring challenges to power systems for the reason of considerable charging load and random nature of their net load consumption. However, aggregation and coordination of EVs (especially EVs with vehicle-to-grid (V2G) capability) offer new opportunities to grid operators by providing the possibility of charging/discharging cycle control of their batteries. On the other hand, energy storage systems (ESSs) are one of the most applicable distributed energy resources (DERs) with growing penetration level in the last decades. The optimal coordination and schedule of ESSs,... 

In this work, a method for increasing the storage capability of a solar thermal energy system has been discussed. The system includes two tanks with the flexibility in choosing the best storage medium on the basis of the solar collector's outlet temperature. The results show that using such a hybrid storage system, the storable energy can be increased. Comparing the results with those for simple common storage systems, the extent of improvement was calculated. For verification of the results, a small pilot system was assembled. The test apparatus operated during 2008-2009 cold months and the parameters were recorded. Comparison of the theoretical and experimental results showed a good... 

Energy storage systems are expected as a near-term solution for renewable energy application in the residential energy hubs. Within this context, this study investigates the feasibility of using storage systems in improving the technical and financial performance of the residential renewable-based energy hub. A new approach has been proposed in this study in which economic dispatch problem has been formulated for an energy hub including both electrical and heat storage system. The proposed approach determines the optimal supply of energy demand and storage system operation to minimise the total energy cost of the hub. The economic benefit of storage system due to energy cost saving and... 

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... 

The widespread use of cloud computing services raises the question of how one can delegate the processing tasks to the untrusted distributed parties without breaching the privacy of its data and algorithms. Motivated by the algorithm privacy concerns in a distributed computing system, in this paper, we introduce the private function retrieval (PFR) problem, where a user wishes to efficiently retrieve a linear function of K messages from N non-communicating replicated servers while keeping the function hidden from each individual server. The goal is to find a scheme with minimum communication cost. To characterize the fundamental limits of the communication cost, we define the capacity of PFR... 

With the current focus on energy and the environment, efficient integration of renewable energies, especially solar energy into power systems, is becoming indispensable. Moreover, to fully capture solar potentials and to recognize the unique characteristics associated with solar energy in power systems reliability assessment, a profound investigation is needed. Accordingly, this paper attempts to establish a comprehensive analytical approach for modeling the reliability of a hybrid system (Photovoltaic (PV) system with Energy Storage System (ESS)). To this end, the output of the PV system is modeled by a multi-state model, and the ESS system is modeled as a two-state Markov model. Moreover,... 

The wear-out of flash-based Solid-State Drives (SSDs) is a main concern that significantly affects their reliability. One major parameter that accelerates SSD wear-out is the number of write-cycles committed to flash chips. The number of write-cycles in SSD-based disk subsystem is highly dependent on the erasure code implemented in Redundant Array of Independent Disks (RAIDs). In this paper, we investigate the impact of erasure codes and the configuration of storage subsystems (i.e., the number of disks participated in the RAID array and stripe unit size) on the endurance of storage systems. The number of write-cycles is considered as a metric to evaluate the endurance of storage system. We... 

In this article, a solar absorption chiller used in MehrAbad region of Tehran, Iran is optimized with exergoeconomic principles and genetic algorithm. After optimizing, a storage system with Phase Change Material technique (PCM) is designed for this optimum configuration for supporting system when sunshine is not received adequately, especially at night. Exergoeconomic analysis is based on finding some ways to improving the performance of a thermal system considering economic constrains. In this study, the exergoeconomic optimization is applied for LiBr-water absorption. The results show that total investment cost of main system, the whole of system except storage system, has increased... 

Erasure codes are widely used in data storage systems to protect against disk failures. Employing erasure codes in an array of Solid-State Drives (SSDs) in storage systems necessitates designers to revisit different characteristics in comparison to Hard Disk Drives (HDDs), due to non-mechanical property of SSDs. One of the most important characteristics of SSDs is their limitation on the number of Program/Erase (P/E) cycles. By taking into account the characteristics of SSDs, this paper presents a comprehensive analysis to investigate the effects of three well-known erasure codes on the endurance and performance of SSD-based disk subsystems. The three erasure codes, i.e., Reed-Solomon,... 

Increased electricity demand coupled with investment in renewable-based generating units has resulted in problems such as transmission congestion and load shedding in modern power systems. In this situation, transmission expansion planning (TEP) studies plays a key role in dealing with the aforementioned problems. On the other hand, deployment of energy storage systems (ESSs) has been regarded as a viable solution for effective exploitation of renewable resources. In this context, this paper develops a novel framework to investigate the impacts of storage facilitates on the transmission expansion planning problem. The presented framework is decomposed to investment and operation subproblems... 

Nowadays, the energy storage systems (ESSs) are widely used in different level of power systems for dealing with the challenges caused by the integration of renewable energy sources (RESs). Among the ESSs, batteries are more suitable for being used in microgrids (MGs) at distribution level due to their special features. Therefore, this paper presents a novel approach for planning of distributed battery energy storage systems (BESSs) to enhance MGs operation, economically. The model is formulated as a mixed integer nonlinear programming problem (MINLP) and considers various types of BESSs. In order to verify the effectiveness of the proposed approach, it is applied to the IEEE 33-bus network... 

Deployment of battery energy storage system (BESS) is a viable option to alleviate the inherent power fluctuation of wind farms. In this paper, a novel model predictive control (MPC) scheme is presented in order to control the BESS dispatch in an integrated wind farm. The constraints of BESS are formulated and are taken into account in optimization problem. The predictive control is based on receding horizon which shows robustness and improved performance compared to the conventional BESS control strategies. The objective function is defined in order to minimize the deviation of wind power production relative to the scheduled production. The results showed the effectiveness of the proposed... 

This paper provides a new multi-objective (MO) framework for expansion studies of energy storage systems (ESSs) in high wind penetrated power system. The proposed approach well considers the issues originated from the wind power curtailment via introducing expected of wind curtailment cost as an objective function of the studies. All other imposed costs of installing storage units are modeled as expected of total social cost. Also, the effect of uncertainties is modeled through an internal scenario analysis. In this regard, two criteria including maximum regrets of wind curtailment cost and total social cost are considered as the other objectives of the proposed MO optimization procedure....