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    			    MOHAMED ABOUTABL

    will be held on 	    Tuesday, October 26, 1999 at 2:30 p.m. 
			    A. V. Williams Building, Room 4185 

    Title of Dissertation:  Temporarily-Determinate Disk Access for 
			    Real-Time Applications

    Abstract:  Magnetic disk drives are by far the most commonly used
medium for online data storage. Throughout the years, disk drives have
rapidly grown in capacity and reliability. Meanwhile, the cost per
megabyte of storage has decreased by even a faster rate.  Recently, a new
wave of real-time applications that heavily rely on accessing
disk-resident databases have emerged. These applications cover fields as
diverse as video-on-demand servers, image recognition and pattern matching
in industrial control and military applications. It becomes necessary that
new techniques be developed in order to provide such real-time
applications with a temporally deterministic disk service. Current
techniques exhibit large variance in the service time experienced by
individual input/output (I/O) requests. This variance is usually due to
the inaccurate modeling of the mechanical and temporal characteristics of
disk drives.

In this thesis, we establish a comprehensive software architecture whose
primary task is to meet the temporal restrictions imposed by real-time
applications that require disk access. We provide a set of software-based
techniques which extract those mechanical and temporal characteristics of
disk drives required to build an accurate disk model. This model is used
to provide real-time guarantees regarding the service time of I/O
requests. Furthermore, we also develop a new real-time disk scheduling
algorithm and compare its performance against a traditional non real-time
algorithm. A high-precision real-time dispatching technique is also
developed. This technique dispatches real-time tasks at the predetermined
start times with an
accuracy of few CPU clock ticks. Collectively, these contributions make
up some of the essential building blocks of a real-time file system.	
            
    Examinine Committee:    Dr. Ashok Agrawala, Chair
		            Dr. Charles B. Silio,E.E, University Rep
			    Dr. Jeffrey Hollingsworth 
			    Dr. A. Udaya Shankar
			    Dr. Mohamed Farag Younis, Special Member

	     MEMBERS OF THE GRADUATE FACULTY ARE INVITED TO ATTEND.