A note on "The Need for End-to-End Evaluation of Cloud Availability"
  Cloud availability is a major performance parameter for cloud platforms, but there are very few measurements on commercial platforms, and most of them rely on outage reports as appeared on specialized sites, providers' dashboards, or the general press. A paper recently presented at the PAM 2014 conference by Hu et alii reports the results of a measurement campaign. In this note, the results of that paper are summarized, highlighting sources of inaccuracy and some possible improvements. In particular, the use of a low probing frequency could lead to non detection of short outages, as well as to an inaccurate estimation of the outage duration statistics. Overcoming this lack of accuracy is relevant to properly assess SLA violations and establish the basis for insurance claims. 
Maurizio Naldi
cs.DC