What storage engines work with Oracle

If you have already got an EMC then SRDF is the obvious choice, tho' Veritas Volume Replicator may be an option. SAN is not something you usually buy "off the shelf" the first time, the vendor will work with you to establish your requirements, both for performance and resilience. Other vendors you may which to consider are HDS, 3Par and NetApp.

However my recommendation is to not use the storage for this, use Data Guard because a) it's free once you already have paid for an oracle license and b) it enables Active Standby, something that I am very excited about myself.

As your own question answers: "Oracle Applications is an [ERP]." An "Oracle Apps DBA" will be someone who is experienced in working with the particular schema and tooling around this ERP. There are hundreds (if not thousands) of packages, tables, stored procedures, and interfaces that are specifically built for the ERP. It is not a trivial database to admin. You can get a brief glimpse into some of the things in their ERP by looking around - for example, this blog - or by logging into a Metalink account as someone who is a customer of their ERP solution, where you can get ERDs and other documentation.