Sharif Digital Repository

Nowadays, leakage energy constitutes up to 80% of total cache energy consumption and tag array is responsible for a considerable fraction of static energy consumption. An approach to reduce static energy consumption is to replace SRAMs by STT-RAMs with near zero leakage power. However, a problem of an STT-RAM cell is its limited write endurance. In spite of previous studies which have targeted the data array, in this study STT-RAMs are used in the L1 tag array. To solve the write endurance problem, this study proposes an STT-RAM/SRAM tag architecture. Considering the spatial locality of memory references, the lower significant bit-lines of the tag update more. The SRAM part handles the... 

In recent years, high interest in using virtualization platforms and Virtual Machines (VMs) in enterprise data centers and Clouds has significantly increased the demand for high performance data storage systems. Recent studies in virtualized platforms have suggested using high-performance storage elements such as Solid-State Drives (SSDs) as a caching layer for storage subsystems mainly built upon Hard Disk Drives (HDDs). Such studies implicitly focus on sharing and partitioning the I/O cache space between VMs, while they neglect to address other important parameters such as SSD lifetime, reliability, and cache policies, which can significantly affect the efficiency of I/O caching in terms... 

The increasing growth of digital data and the use of data-intensive applications and cloud computing have made data storage systems the performance bottlenecks of computing systems. To improve the efficiency of data storage systems and enhance the quality of service, storage system manufacturers use high-performance storage devices such as solid-state drives (SSDs) in their designs, namely, all-flash storage systems. SSDs provide significant performance compared to hard disk drives and are used in the architecture of high-speed storage systems. Despite very high speed of SSDs, their high price and low endurance have limited their usage in data storage systems. The limited endurance of SSDs... 

The performance gap between main memory and storage devices is one of major bottlenecks in data storage systems. I/O caches are one way to reduce this performance gap. In recent years, open source I/O cache modules such as OpenCAS, EnhanceIO, and dm-cache have been examined by researchers from the performance perspective, but the reliability of these modules has not been investigated and compared. In this thesis, we evaluate the reliability of I/O cache modules against hardware failures (e.g., power failure) and software failures (e.g. operating system failure). In addition, we examine the reliability mechanisms in these three modules, whose fault models and their failure rates significantly...