Forecasting Disk Resource Requirements for a Usenet Server
Karl L. Swartz
Stanford Linear Accelerator Center
Abstract
Three years ago the Stanford Linear Accelerator Center (SLAC) decided
to embrace netnews as a site-wide, multi-platform communications tool
for the laboratory's diverse user community. The Usenet newsgroups as
well as other world-wide newsgroup hierarchies were appealing for
their unique ability to tap a broad pool of information, while the
availability of the software on a number of platforms provided a way
to communicate to and amongst the computing community. The previous
way of doing this ran only on the VM mainframe system and had become
increasingly ineffective as users migrated to other platforms. The
increasing dependence on netnews brought with it the requirement that
the service be reliable. This was dramatically demonstrated when the
long-neglected netnews service collapsed under the load of the
traditional fall surge in Usenet traffic and the site was without news
service for a week while an upgraded system was installed. One result
of that painful event was that efforts were made to forecast growth
and the accompanying hardware requirements so that equipment could be
acquired and installed before problems became visible to the
users. This paper describes the major on-disk databases associated
with news software, then presents an analysis of the storage
requirements for these databases based on data collected at SLAC. A
model is developed from this data which permits forecasting of disk
resource requirements for a full feed as a function of time and local
policies. Suggestions are also made as to how to modify this model for
sites which do not carry a full feed.
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