6,685 research outputs found
A Study of Disk Performance Optimization.
Response time is one of the most important performance measures associated with a typical multi-user system. Response time, in turn, is bounded by the performance of the input/output (I/O) subsystem. Other than the end user and some external peripherals, the slowest component of the I/O subsystem is the disk drive.
One standard strategy for improving I/O subsystem performance uses high-performance hardware like Small Computer Systems Interface (SCSI) drives to improve overall response time. SCSI hardware, unfortunately, is often too expensive to use in low-end multi-user systems. The low-end multi-user systems commonly use inexpensive Integrated Drive Electronics (IDE) disk drives to keep overall costs low. On such IDE based multi-user systems, reducing the Central Processing Unit (CPU) overhead associated with disk I/O is critical to system responsiveness.
This thesis explores the impact of PCI bus mastering Direct Memory Access (DMA) on the performance of systems with IDE drives. DMA is a data transfer protocol that allows data to be sent directly from an attached device to a computer system’s main memory, thereby reducing CPU overhead. PCI bus mastering allows modern IDE disk controllers to manipulate main memory without utilizing motherboard-resident DMA controllers.
Using a series of experiments, this thesis examines the impact of PCI bus mastering DMA on IDE performance for synchronous I/O, relative to Programmed Input/Output (PIO) and SCSI performance. Experiment results show that PCI bus mastering DMA, when used properly, improves the responsiveness and throughput of IDE drives by as much as a factor of seven. The magnitude of this improvement shows the importance of operating system support for DMA in low-end multi-user systems. Additionally, experimental results demonstrate that performance gains associated with SCSI are dependent on system usage and operating system support for advanced SCSI capabilities. Therefore, under many circumstances, high-performance SCSI drives are not cost effective when compared with IDE bus mastering DMA capable drives
SimpleSSD: Modeling Solid State Drives for Holistic System Simulation
Existing solid state drive (SSD) simulators unfortunately lack hardware
and/or software architecture models. Consequently, they are far from capturing
the critical features of contemporary SSD devices. More importantly, while the
performance of modern systems that adopt SSDs can vary based on their numerous
internal design parameters and storage-level configurations, a full system
simulation with traditional SSD models often requires unreasonably long
runtimes and excessive computational resources. In this work, we propose
SimpleSSD, a highfidelity simulator that models all detailed characteristics of
hardware and software, while simplifying the nondescript features of storage
internals. In contrast to existing SSD simulators, SimpleSSD can easily be
integrated into publicly-available full system simulators. In addition, it can
accommodate a complete storage stack and evaluate the performance of SSDs along
with diverse memory technologies and microarchitectures. Thus, it facilitates
simulations that explore the full design space at different levels of system
abstraction.Comment: This paper has been accepted at IEEE Computer Architecture Letters
(CAL
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