How do people measure the value (ITIL) of a service within JSM?

[Tom langton]

We have all our services within the CMDB and are really keen to measure how well they are performing for the business.  We are looking to combine the Utility (mainly from service review feedback) with the Warranty (mainly incidents from the service desk).

Ideally we would like to combine these in a matrix per service/application and then be able to rank these for the whole estate . 

The reason for wanting to track this is to allow us to fully understand our costs, supplier relationship and enable us to make decisions for the portfolio going forward

Thanks