I’m using eSATA drives so I can do server backup with BitLocker. I attached a couple of eSATA drives to a Windows Server 2008 R2 Enterprise machine. After booting the machine, the drives appeared in Disk Management as Offline:
“The disk is offline because of policy set by an administrator”: Huh? I didn’t set no stinking policy about offline disks!
Set eSATA Drives to Go Online Automatically
While it is possible to right-click on the drive in Disk Management and set it Online, I wanted to understand and change the policy. Edward Haletky put me on the right track in this post. Apparently the Enterprise and Datacenter editions of Server 2008 set the default SAN policy to Offline Shared (see this TechNet blog post). For some reason, eSATA drives are treated as SAN disks, so they are also offline by default.
All that is needed is to use diskpart to change the SAN policy to OnlineAll:
Once that is done, the drive mounts automatically when it is attached:
For more information on the offline modes, type help san while in diskpart.
The cited posts refer to explicitly disabling read-only mode, but I found that at least with eSATA drives, all that is necessary is to change the SAN policy to OnlineAll and to reconnect the drive.