I have just ordered a new rig for my business. We do a lot of software development for Microsoft SharePoint and need the rig to run several virtual machines for development and test purposes. We will be using the free VMware ESXi for virtualization. For a start, we plan to build and start the following VMs - all with Windows Server 2008 R2 x64:

• Active Directory server
• MS SQL Server 2008 R2
• Automated Build Server
• SharePoint 2010 Server for hosting our public Web site and our internal Intranet for a few people. The load on this server is going to be quite insignificant.
• 2xSharePoint 2007 development server
• 2xSharePoint 2010 development server

Beyond that we will need to build several SharePoint farms for testing purposes. These VMs will only be started when needed. The specs of the new rig is:

• Dell R610 rack server
• 2xIntel XEON E5620
• 48GB RAM
• 6x146GB SAS drives
• Dell H700 RAID controller

We believe the new server is going to make our VMs perform a lot better than our existing setup (2xIntel XEON, 16GB RAM, 2x500 GB SATA in RAID 1). But we are not sure about the RAID level for the new rig.

Should we go for having the the 6x146GB SAS drives in a RAID 10 configuration or a RAID 5 configuration? RAID 10 seems to offer better write performance and lower risk of a RAID failure. But it comes at a cost of less drive space. Do we need RAID 10 or would RAID 5 also be a good choice for us?