If you have Enterprise Servers you should read this blog
I feel that a DBA should have a good working understanding of the underlying server that SQL Server sits upon and the storage system(s) that it connects to, otherwise you may not know if you're being spun a yarn when you're trying to understand performance issues which may or may not be outside SQL Server. One of my favourite microsoft teams are the Core , http://blogs.technet.com/askcore/
Have a read it has some great stuff.