I have been reading that some users of VMWare ESX are having their storage disappear upon upgrading from v5 to v6. Something about having to change back from SCST to IETd.

What is the point of upgrading if we can't use the new SCST protocol?

As well, My environment needs to be accessible pretty much 24/7 with minimal downtime. What are people's experiences with the upgrade process and if I run in to problems, what is the average remediation timeframe?