Hi,
as you know, the B110i RAID is a software raid and you will not be able to create a raid 1 between the 2nd and 3rd disk.
As it seems to me that buying a "true" raid controller is not an option (and so also buying some software is not an option), I think that you can try to leverage GhettoVCB script (http://communities.vmware.com/docs/DOC-8760) to backup your VM from disk 2 to disk 3: depending on the size of your VM you can have more frequent backups (hourly backup for example).
This is not a true fault tolerance or ha settings, think of it as a kind of "smart backup": If/when a disk fail, you can start the VM from the other disk.
Giuseppe
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Giuseppe
@gguglie
vExpert 2011