112 research outputs found
Rodney Van Meter
No full textCurrent generations of hard disk drives use a technique known as zoned constant angular velocity (ZCAV), taking advantage of the geometry to increase total disk capacity by varying the number of disk sectors per track with the distance from the spindle. A side effect of this is that the transfer rate also varies with sector address. We analytically estimated and measured this effect on file system performance on a BSD Fast File System, showing a drop of roughly 25% in peak transfer rate depending on head position. We also show that, while ZCAV effects cannot be ignored, a simple linear model adequately estimates the performance from the few parameters normally available in disk drive spec sheets. 1 Introduction Many magnetic disk drives use a technique known as zoned constant angular velocity (ZCAV), taking advantage of the geometry to increase total disk capacity by varying the number of disk sectors per track with the distance from the spindle. A side effect of this is that the tr..
When entanglement meets classical communications: Quantum Teleportation for the Quantum Internet
No full textQuantum Teleportation is the key communication functionality of the Quantum Internet, allowing the 'transmission' of qubits without the physical transfer of the particle storing the qubit. Quantum teleportation is facilitated by the action of quantum entanglement, a somewhat counter-intuitive physical phenomenon with no direct counterpart in the classical word. As a consequence, the very concept of the classical communication system model has to be redesigned to account for the peculiarities of quantum teleportation. This re-design is a crucial prerequisite for constructing any effective quantum communication protocol. The aim of this manuscript is to shed light on this key concept, with the objective of allowing the reader: i) to appreciate the fundamental differences between the transmission of classical information versus the teleportation of quantum information; ii) to understand the communications functionalities underlying quantum teleportation, and to grasp the challenges in the design and practical employment of these functionalities; iii) to acknowledge that quantum information is subject to the deleterious effects of a noise process termed as quantum decoherence. This imperfection has no direct counterpart in the classical world; iv) to recognize how to contribute to the design and employment of the Quantum Internet.</p
Author Guidelines for MSS Symposium Proceedings
No full textThe abstract is to be in fully-justified italicized text, at the top of the left-hand column, below the author and affiliation information. Use the word “Abstract ” as the title, in 12-point Times, boldface type, centered relative to the column, initially capitalized. The abstract is to be in 10-point, single-spaced type. The abstract may be up to 3 inches (7.62 cm) long. Leave two blank lines after the Abstract, then begin the main text. 1
SLEDs: Storage Latency Estimation Descriptors
No full textManaging the latency of storage systems is a key to creating effective very large scale information systems, such as web interfaces to satellite image databases and video-on-demand servers. Storage Latency Estimation Descriptors (SLEDs) are architecture-independent descriptions of the retrieval time of a unit of data. They describe the latency to the first byte, and the bandwidth expected. SLEDs are an important enabling technology for true end-to-end quality of service (QoS) because they can be used to predict and schedule data transfer with multimedia (guaranteed I/O rate) file systems. SLEDs provide the interface that allows database management systems (DBMS) and clients of hierarchical storage management (HSM) systems to optimize their data access patterns by choosing to read data in specific sequences or not at all. SLEDs are designed to work in intra-machine, local-area network (LAN) and wide-area network (WAN) storage systems, and to scale through twelve orders of magnitude in l..
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