Performance Analysis and Optimization of the Hurricane File System ...

Chapter 1
Introduction and Motivation
Computer system performance is one metric of technological advancement. Scientists and engineers are
constantly pushing the performance envelope. Due to the efforts of mathematicians, physicists, chemists,
electrical engineers, and computer engineers, the “law” of Gordon Moore [46] is maintained. Moore pre-
dicted that the number of transistors on an integrated circuit would double every 18 months. Along with
this exponential rate of microprocessor improvement, other techniques have been applied to yield further
performance improvements in computer systems.
To obtain additional hardware improvements, computer scientists and engineers often use the technique
of increasing computer system size. Scaling up the size of a computer system involves increasing the amount
of various resources such as the number of microprocessors, the amount of memory, the number of mem-
ory banks, the number of disks, and the capacity of inter-connections between these components. Scalable
computer systems exist in a spectrum [37, p. 130] ranging from those constructed as a large tightly-coupled
monolithic computer, to those constructed out of many inter-connected loosely-coupled commodity comput-
ers.
Regardless of the style of computer system, software performance has not kept pace with the underlying
hardware performance [52, 3, 41]. Therefore, software scalability is an important aspect to consider when
evaluating the performance of large computer systems. It comes down to the question of whether software
performance increases proportionately with increases in hardware resources or performance.
One of the fundamental causes of the software scalability problem is the operating system (OS). Many
Unix-based large computer systems rely on retro-fitted operating systems that were initially designed for
small uniprocessor computers [22, p. 4] [18]. While these operating systems extend basic functionality
to include the larger set of resources, they are unable to fully exploit the performance potential of these
computer systems. The ad hoc approach used to transform a uniprocessor operating system into a large-
scale multiprocessor operating system appears to be inadequate. Rather, large-scale multiprocessor operating
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