Report Number: CS-TR-87-1177
Institution: Stanford University, Department of Computer Science
Title: Log Files: An Extended File Service Exploiting Write-Once
Author: Finlayson, R. S.
Author: Cheriton, D. R.
Date: August 1987
Abstract: A log service provides efficient storage and retrieval of
data that is written sequentially (append-only) and not
subsequently modified. Application programs an subsystems use
log services for recovery, to record security audit trails,
and for perforrnance monitoring. Ideally, a log service
should accomodate very large, long-lived logs, and provlde
efficient retrieval and low space overhead.
In this paper, we describe the design and implementation of
the Clio log service. Clio provides the abstraction of log
files: readable, append-only files that are accessed in the
same way as conventional files. The underlying storage medium
is required only to be append-only; more general types of
write access are not necessary. We show how log files can be
implemented efficiently and robustly on top of such storage
media - in particular, write-once. optical disk. In addition,
we describe a general application software storage
architecture that makes use of log files.