Performance Analysis of the Unitree Central File

This report consists of two parts. The first part briefly comments on the documentation status of two major systems at NASA#s Center for Computational Sciences, specifically the Cray C98 and the Convex C3830. The second part describes the work done on improving the performance of file transfers between the Unitree Mass Storage System running on the Convex file server and the users workstations distributed over a large georgraphic area

Evaluating the Effect of Online Data Compression on the Disk Cache of a Mass Storage System

A Unix based mass storage file system which provides access to the stored data only through the ftp protocol has provided the incentive to examine the performance of inserting an online data compression algorithm at each client in order to increase the effective capacity of the storage system. Two online compression algorithms were tested, namely the Ziv-Lempel (gzip) and LZW (compress) algorithms, using both a sequential and a pipelined implementation. Their performance was compared based on their execution time and the compression ratio attained for different types of files. 1 Introduction Mass storage systems are used in research environments for storing data generated by scientific simulations and satelite observations in amounts on the order of terabytes. The cost of storage devices of that capacity is still very high while the rate of increase in disk space requirements by the users grows continuously. This problem is especially evident in scientific research centers where enor..

Performance Modeling of Network-Attached Storage Device Based Hierarchical Mass Storage Systems

Network attached storage devices improve I/O performance by separating control and data paths and eliminating host intervention during the data transfer phase. Devices are attached to both a high speed network for data transfer and to a slower network for control messages. Hierarchical mass storage systems use disks to cache the most recently used files and a combination of robotic and manually mounted tapes to store the bulk of the files in the file system. This paper shows how queuing network models can be used to assess the performance of hierarchical mass storage systems that use network attached storage devices as opposed to host attached storage devices. Simulation was used to validate the model. The analytic model presented here can be used, among other things, to evaluate the protocols involved in 1/0 over network attached devices

Automated Clustering-Based Workload Characterization

This paper presents the design and discusses the implementation of a tool for workload characterization of mass storage systems. The main features of the tool discussed here are: . ######### ####### ### ########### #############: histograms of system activity are generated and presented to the user for peak-period determinatio

An Analytic Model of Hierarchical Mass Storage Systems with Network-Attached Storage Devices

Network attached storage devices improve I/O performance by separating control and data paths and eliminating host intervention during data transfer. Devices are attached to a high speed network for data transfer and to a slower network for control messages. Hierarchical mass storage systems use disks to cache the most recently used files and tapes (robotic and manually mounted) to store the bulk of the files in the file system. This paper shows how queuing network models can be used to assess the performance of hierarchical mass storage systems that use network attached storage devices. The analytic model validated through simulation was used to analyze many different scenarios. 1 Introduction Most current mass storage systems at national laboratories and supercomputer centers are based on the server attached storage model in which all storage devices are attached to a single machine using high speed busses and I/O channels. A request for access to a storage object arrives at the ser..

Analytical Modeling Of Robotic Tape Libraries Using Stochastic Automata

. This paper presents results of preliminary work concerning the analytical modeling of a robotic tape library using stochastic automata. This model is a first approximation which we use to test the efficiency and accuracy of stochastic automata networks as a modeling tool. The effects of interactive get and put requests, migration, and purging at online and nearline layers of a tertiary storage device are investigated. The discussion in this paper sheds further light to the merits and limitations of stochastic automata networks as a modeling methodology for evaluating the performance of complex real life applications. Key words. Robotic tape libraries, stochastic automata networks, Markov chains, numerical solution techniques 1 Introduction Scientific projects, such as the Earth Observing System (EOS), climate modeling, and magnetic energy fusion modeling, generate terabytes of data that must be archived and made available for further processing and analysis. Data management systems ..

Pythia and Pythia/WK: Tools for the Performance Analysis of Mass Storage Systems

This paper describes the design and operation of two tools, Pythia and Pythia/WK, that assist system managers and integrators in making cost-effective procurement decisions. Pythia automatically buids and solves an analytic model of a mass storage system based on a graphical description of the architecture of the system and on a description of the workload imposed on the system. The use of a modeling wizard to perform this conversion from a graphical description of a mass storage system to an analytic model makes Pythia unique among analytic performance tools. Pythia/WK uses clustering algorithms to characterize the workload from the log files of the mass storage system. The resulting workload characterization is used as input to Pythia. KEY WORDS Mass storage systems object oriented design workload characterization graphical user interfaces performance prediction tool Tcl/Tk CCC 0038--0644/96/000001--28 c fl1996 by John Wiley & Sons, Ltd. 2 O. I. PENTAKALO