  Distributed systems in general and cloud systems in particular, are
susceptible to failures that can lead to substantial economic and data losses,
security breaches, and even potential threats to human safety. Software ageing
is an example of one such vulnerability. It emerges due to routine re-usage of
computational systems units which induce fatigue within the components,
resulting in an increased failure rate and potential system breakdown. Due to
its stochastic nature, ageing cannot be directly measured, instead ageing
indicators as proxies are used. While there are dozens of studies on different
ageing indicators, their comprehensive comparison in different settings remains
underexplored. In this paper, we compare two ageing indicators in OpenStack as
a use case. Specifically, our evaluation compares memory usage (including swap
memory) and request response time, as readily available indicators. By
executing multiple OpenStack deployments with varying configurations, we
conduct a series of experiments and analyze the ageing indicators. Comparative
analysis through statistical tests provides valuable insights into the
strengths and weaknesses of the utilised ageing indicators. Finally, through an
in-depth analysis of other OpenStack failures, we identify underlying failure
patterns and their impact on the studied ageing indicators.
