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  5. What Should I Do When a Disk Goes Offline?

What Should I Do When a Disk Goes Offline?

Symptom

A disk attached to a Windows ECS is offline, and the system displays the message "The disk is offline because of policy set by an administrator."

Figure 1 Offline disk

Possible Causes

Windows has three types of SAN policies: OnlineAll, OfflineShared, and OfflineInternal.

Table 1 SAN policies

SAN Policy

Description

OnlineAll

Indicates that all newly detected disks are automatically brought online.

OfflineShared

Indicates that all newly detected disks on sharable buses, such as FC or iSCSI, are left offline by default, while disks on non-sharable buses are kept online.

OfflineInternal

Indicates that all newly detected disks are left offline.

The SAN policy of certain Windows OSs, such as Windows Server 2008/2012 Enterprise Edition and Data Center Edition, is OfflineShared by default.

Solution

Use the disk partition management tool DiskPart to obtain and set the SAN policy on the ECS to OnlineAll.

  1. Log in to the Windows ECS.
  2. Press Win+R to run cmd.exe.
  3. Run the following command to access DiskPart:

    diskpart

  4. Run the following command to view the SAN policy on the ECS:
    san
    • If the SAN policy is OnlineAll, run the exit command to exit DiskPart.
    • If the SAN policy is not OnlineAll, go to step 5.
  5. Run the following command to change the SAN policy to OnlineAll:

    san policy=onlineall

  6. (Optional) Use the ECS with the SAN policy changed to create a private image to make the configuration take effect permanently. After an ECS is created using this private image, the disks attached to the ECS are online by default. You only need to initialize them.