Very slow shutdown and start with pRDM

Hello,

there is one VM on my ESXi 5.1 host, which shutdown and starts veryl slowly. It is a Windows Server 2008 R2 fileserver with 12 pRDM attached. All other VM (no pRDM or at max two) are performing great.

I'm thinking about the pRDM disks are the problem. Do pRDM affect a VM in this way?

Thanks in advance.