Ok, my Hyper-V Server 2012 looks like this: we currently have 2 VM's in production, one is running SharePoint 2010, and the other is hosting the SQL Server 2008 R2 for SharePoint.
We're getting ready to add another VM for hosting a Ecommerce Web Store for our website. I found one that's open-source and uses MSSQL Server (nopCommerce). My question is: what is best practice for SQL server role here? Should I use our existing SQL Server (currently hosting SharePoint) to host both databases side-by-side? Or should I install a local instance of SQL Server on the WebStore VM, so I end up with 2 VMs dedicated for SharePoint and 1 VM dedicated for Web Store? Or should I even create another SQL Server VM for the Web Store, so I have 2 VMs for SharePoint and 2 VMs for Web Store? (This one seems resource-expensive to me.)
And we have additional consideration: Our Inventory tracking system is currently being hosted as a Access Web-App DB on SharePoint. We want our Inventory data to populate the Web Store. From my Googling around, it seems like linking together SQL databases isn't too big of a deal and happens quite a bit. But I'm not familiar with SQL Best Practices yet, I don't know if that's more of a case for keeping the databases on the same server or not.