What's a good way to utilize the two disks for your datastore? Run mongodb for example one disk and backup to the other? Run one sharded instance on one disk and another sharded instance on the other disk?
With MySQL (and Oracle before that) it was common to simply move different parts of the database data files to different disks. I don't use Mongo so I can't speak to that, but the concept works pretty much universally. See here for more information about spreading your database around multiple disks: http://www.mysqlperformanceblog.com/2010/12/25/spreading-ibd...
