Once you have subscribed to a specific cloud service, how can you monitor the quality of that service?

Assuming you are providing a service within the cloud, the quality of that service is usually expressed in two ways.  First - what percent of the time is the service available to cloud users?  Secondly, when a service is requested, how long does it take between the request and the consumption of the service by the cloud user?

Most cloud providers provide empirical data showing the overall availability of the cloud platform.  That's a start.  In addition, some cloud providers have recently announced the capability for cloud publishers to incorporate monitoring in their applications that they are publishing in the cloud.  So, this is becoming available.

Probably, the best way to monitor service is to do it yourself by using a synthetic transaction generator.  The transaction generator can send messages to the cloud,  requesting services,  and then measure the end-to-delay when the service is delivered.  If there is no response, then that information is used to calculate availability.  A number of commercial transaction generators are available today to do this.

Roger,

Good question, especially in light with the Twitter hack that occurred in Google's cloud recently.  Security is a combination of hardware, software and processes.  Most clouds that are available today are not enterprise-quality regarding security.  But there are new ones being announced that capitalize not only on unique security technologies, but also well proven security practices.  Look for the appropriate certifications, such as the

ISO 27001:2005 certification.  Insist on understanding the entire "chain of custody" from the transmission of data to its storage.  This needs to be established and monitored to ensure that multi-tenant clouds provide safe "communities of interest" for their individual customers.