Storage Spaces adding a mirrored drive later

Solution 1:

You can add disks to the pool without problems, but it is the virtual disk you build on top of the pool that controls the "resiliency" setting.

So, you can do this:

1. add a new Pool to Storage Spaces containing only one disk
2. add a virtual disk using the pool you just created (its resiliency setting will be "simple" since you only have one disk in the pool)
3. Add more disks to you existing pool

However, you can not increase the resiliency of your vdisk using the new disks. You basically have to add another vdisk and manually move data from the "simple" vdisk to the "resilient" one.

This seems to confirm it:

http://social.technet.microsoft.com/Forums/windowsserver/en-US/4c3ef0c3-283e-42ee-9ad9-31d83287339d/server-2012-change-virtual-disk-volume-layout