I'm trying the new "Storage Pools" feature on Windows Server 2012, and I've created several disks on the pool.

When I restart the server, some of the disks (two, out of four) do not attach automatically, and don't show up in the list of disks.

I can go to Server Manager > File and Storage Services > Storage Pools, and the faulty disks are listed with a yellow triangle beside them. The drive health in the properties are "unknown".

But if I right-click and choose attach, the disk comes online, with all the content on it intact. But after another restart, it's the same story.

I didn't find any relevant event in the event log, how can I find out why the drives are not attaching?