I installed a dedicated disk in a Windows Server 2012 R2 server and configured Windows Server Backup to use it. This works great until the disk fills up. When it does, an error is logged "The shadow copies of volume \\?\Volume<GUID> were deleted because the shadow copy storage could not grow in time. Consider reducing the IO load on the system or choose a shadow copy storage volume that is not being shadow copied."
I've read that when the disk fills up, WSB is supposed to delete the oldest backup and continue, but it is deleting everything and starting over.
I've seen other posts indicating that this behavior was observed in Windows Server 2008 R2, but is broken in 2012+. Is there some way to get automatic retention working in 2012 R2?