"Optimistic Parallel Simulation of a Large-Scale View Storage System"
G. Yaun, C. D Carothers, S. Adali and D. Spooner
Future Generation on Computer Systems
(FCGS), Volume 19, Number 4, pages 479-492, November, 2003
ABSTRACT
In this paper we present the design and implementation of a complex
view storage system model. Here, a hierarchy of view storage servers
are connected to an array of client-side local disks. The term {\em
view} refers to the output or result of a query made on the part of an
application that is executing on a client machine. These queries can
to be arbitrarily complex and formulated using SQL. The goal of this system
is to reduce the turnaround time of queries by exploiting locality
both at the local disk level as well as between clients and servers
prior to making the request to the highest level database server.
This model has been designed for execution with an optimistic
simulation engine. One of the primary drawbacks of this parallel
synchronization mechanism has been high overheads due to
state-saving. We attack this problem by implementing the model using
reverse computation. Here, the event processing routines are made
reversible, which avoids having incrementally state-saving values that
can be reverse computed, such as ++ and --. Destructive
assignments of the form a=b are saved using a swap
operation, which precludes the need for additional state space.
In our performance study of this application, we find that speedups
range from 1.5 to over 5 on 4 processors. Super-linear speedups are
attributed to a slow memory subsystem and the increased availability of
level-1 and level-2 cache when moving to a larger number of processors.