  Cloud computing has achieved great success in modern IT industry as an
excellent computing paradigm due to its flexible management and elastic
resource sharing. To date, cloud computing takes an irrepalceable position in
our socioeconomic system and influences almost every aspect of our daily life.
However, it is still in its infancy, many problems still exist.Besides the
hotly-debated security problem, availability is also an urgent issue.With the
limited power of availability mechanisms provided in present cloud platform, we
can hardly get detailed availability information of current applications such
as the root causes of availability problem,mean time to failure, etc. Thus a
new mechanism based on deep avaliability analysis is neccessary and
benificial.Following the prevalent terminology 'XaaS',this paper proposes a new
win-win concept for cloud users and providers in term of 'Availability as a
Service' (abbreviated as 'AaaS').The aim of 'AaaS' is to provide comprehensive
and aimspecific runtime avaliabilty analysis services for cloud users by
integrating plent of data-driven and modeldriven approaches. To illustrate this
concept, we realize a prototype named 'EagleEye' with all features of 'AaaS'.
By subscribing corresponding services in 'EagleEye', cloud users could get
specific availability information of their applications deployed in cloud
platform. We envision this new kind of service will be merged into the cloud
management mechanism in the near future.
