Sharif Digital Repository

Deduplication is a data reduction technique, which eliminates redundant data by storing only a single copy of each file or block, along with a reference to the unique copy of data. Deduplication reduces the storage space and bandwidth requirements of data storage systems, and becomes more effective when applied across multiple users. All deduplication techniques use cryptographic algorithms to detect duplication instead of byte-by-byte comparison between input data and all previously stored data. In this manner, the data stream is divided into non-overlapping chunks of data. Then, the hash values of non-overlapping chunks create an exclusive criterion to identify duplicates. In this thesis,... 

The lifespan of hard disks greatly affects their performance and reliability. Ensuring the freshness of disks during the procurement process for hardware manufacturing companies is crucial for maintaining efficient production systems. Predicting the approximate lifespan of hard disks involves analyzing their characteristics and operational history. Relying solely on SMART reports for estimating disk lifespan is not reliable due to the potential firmware tampering. Previous studies have primarily focused on SATA disks, investigating the relationship between failures and SMART parameter values, while neglecting SAS disks. However, in this research, we collected SMART reports from approximately... 

Storage subsystem is one of the most important components of a computer system. As more valuable information such as bank transactions are being stored in storage subsystems,occurrence of an unrecoverable error can lead to a much bigger problem. A storage subsystem can be divided into software and hardware part. Previous works focused on fault injection in the higher layers of the storage stack and didn’t consider fault injection at the device driver level. In this thesis, the dependability of storage stack is evaluated using fault injection at the device driver layer. Various hardware and software faults that can occur in hard disks and solid state drives are studied and dependability of... 

In recent years, flash-based Solid State Drives (SSDs), because of their lower power consumption, higher throughput, and resistance against physical damages compared to Hard Disk Drives (HDDs) have confronted ever increasing usage in data center, cloud applications, and enterprise servers. Recently, advantages of using interconnection networks between SSD controller and NAND Flash chips for transferring data and commands have been shown. Interconnection network intrinsically provides many advantages such as maintaining the signal integrity at high frequencies, pipelining support, sharing the communication resources, eliminating communication bottlenecks, and reducing power consumption. The... 

Hard disk drives are the main component of computers for permanent data storage. The security of the stored data is related closely to the air gap between the read-write head and the surface of disk. This gap which is created by the aerodynamic force between head and the disk is altered continually by lateral oscillations of disk. In the extreme condition of zero gap and contact between the protective coating layer and subsequently the magnetic material of the disk with the head, the disk will be scratched and damaged. Therefore, the active or passive control of these vibrations has a particular importance in the technology of manufacturing of hard disks. The first step in active control... 

Responding to the increasing volume and complexity of storage workloads requires continuous design and improvement of storage subsystems. Storage workload behavior such as spatial and temporal locality, request type, and frequency have considerable impact on performance. Hence, performance evaluation and prediction must be performed with respect to workload properties. Moreover, design and implementation of solutions that adapt to workload behavior may further increase the performance and endurance of storage subsystems.One of the key aspects of this thesis is to speed-up the performance evaluation of storage hardware. Three main approaches exist for performance evaluation: simulation,...