Attaching a Shared Disk

Scenarios

Separately purchased shared EVS disks are data disks. In the disk list, the function of such a disk is displayed as Data disk, and the status is displayed as Available. In this case, you need to attach the shared data disk to servers for use.

Prerequisites

• The shared disk status is In-use or Available.
• The account is not in arrears.

Notes and Constraints

If you simply attach a shared disk to multiple servers, files cannot be shared among them. Because there are no mutually agreed data read/write rules among servers, read and write operations from them may interfere with each other, or unpredictable errors may occur. To share files between servers, set up a shared file system or a clustered management system first.

• A shared disk can be attached to a maximum of 16 servers. These servers and the shared disk must be in the same AZ within a region.
• A shared, In-use disk can be attached to other servers only when the maximum number of servers that the disk can be attached to has not been reached.
• All the servers attached with a shared disk must run either Windows or Linux.

  For example, if you attach a shared disk to multiple Windows servers and then detach it from these servers, the shared disk cannot be attached to Linux servers later. This is because Windows and Linux support different file systems and cannot identify the original file system on the disk. Improper operations may damage the original file system.

• A shared disk can only be used as a data disk. It cannot be used as a system disk.
• Cloud servers created from ISO images are only used for OS installation. They have limited functions and cannot have EVS disks attached.
• A shared disk can be attached only when the servers' statuses are Running or Stopped.
• A frozen disk cannot be attached.
• A detached, yearly/monthly system disk purchased together with a server can be re-attached and used as a data disk for any server. If you want to use it again as a system disk, you must attach it to the original server.
• A detached, pay-per-use system disk purchased together with a server can be re-attached and used as a data disk for any server. If you want to use it again as a system disk, you must attach it to a server that uses the same image as the original server.

Attaching the Disk on the EVS Console

1. Log in to the management console.
2. Click in the upper left corner and choose Storage > Elastic Volume Service.

   The Elastic Volume Service page is displayed.

3. Locate the target disk in the list and click Attach.

   Shared disks support batch attachment, so you can attach a shared disk to multiple servers. The left area in the Attach Disk dialog box shows the server list. After you select the target servers, the selected servers will be displayed in the right area.

4. Select the target servers you want to attach the shared disk. Ensure that the disk and servers are in the same AZ. After you select the servers, Data disk is automatically entered as the disk function for each server.

   One device name can be used for one disk only. If a device name has been used, it will no longer be displayed in the drop-down list and cannot be selected.

   Figure 1 Attach Disk
   

5. Click OK.

   A dialog box is displayed, showing "The attaching process is NOT completed yet. You must initialize the disk before using it."

6. Click OK to return to the disk list page.

   The status of the disk is Attaching, indicating that the disk is being attached to the servers. When the disk status changes to In-use, the disk is successfully attached.

Attaching the Disk on the ECS Console

1. Log in to the management console.
2. Click in the upper left corner and select the desired region and project.
3. Choose Compute > Elastic Cloud Server.
4. In the search box above the upper right corner of the ECS list, enter the ECS name, IP address, or ID for search.
5. Click the name of the target ECS.

   The page providing details about the ECS is displayed.

6. Click the Disks tab. Then, click Attach Disk.

   The Attach Disk page is displayed.

7. Select the target disk and specify it as the system disk or a data disk.
   • For Xen ECSs, you can specify a specific device name, such as /dev/sdb.
   • For KVM ECSs, you can specify the disk as the system disk or a data disk but cannot specify a specific device name.
   

   • If no disks are available, click Create Disk in the lower part of the list.
   • For the restrictions on attaching disks, see What Are the Requirements for Attaching an EVS Disk to an ECS?
8. Click OK.

   After the disk is attached, you can view the information about it on the Disks tab.

Follow-Up Operations

If you are attaching a new disk, you must then log in to the server and initialize the disk before it can be used. To learn how to initialize disks, see Initialization Overview.

Helpful Links

If your disk cannot be attached to a server, see Why Can't I Attach My Disk to a Server?

If the attached data disk is not showing up, see Why Can't I View the Attached Data Disk on the Server?