In Windows 2008 the SAN disks may show offline status when you add a new disk. When you try to bring the disk online from Disk management you get a message “Disk is offline due to a policy set by an administrator

In Windows 2008 SAN Policy was introduced to protect data on shared disks. When a disk is presented to the server by modifying ACL on the SAN, the server marks the disk as offline. The disk has to be brought online to be accessible.

You need to use the Diskpart command to set the disks online.

  • Start command prompt as an administrator
  • Type diskpart to invoke diskpart utility

  • To verify your existing SAN policy enter SAN

  • To set all disks online enter san policy=onlineall

  • To make only selected disk online and not set the SAN policy to onlineall you can use the “online disk” switch after selecting identified disk from diskpart.
  • For more configuration parameters type help san