Telcos, at least in times past, really tried to achieve a true 5 9s. I worked for Lucent in 2001 on an ultimately doomed product that was essential to the comp

Telcos, at least in times past, really tried to achieve a true 5 9s. I worked for Lucent in 2001 on an ultimately doomed product that was essential to the company's independent survival, a Media Gateway (https://en.wikipedia.org/wiki/Media_gateway https://en.wikipedia.org/wiki/Media_gateway) to supply the other half of their successful Softswitch Media Gateway Controller product, and my NoVa group worked with the Cincinnati people who were responsible for the 5ESS. One of my tasks was vetting the low level design of the persistent database, and it was intense at all levels. No spinning rust, that's for sure. Point-in-time recovery is a snap compared to that domain.