Attaching a Shared Disk

Scenarios

This section describes how to attach a shared EVS disk to a cloud server. Disks supporting this operation include:

• Separately created data disks
• Detached data disks

Prerequisites

• The shared disk status is In-use or Available.
• The statuses of servers are Running or Stopped.
• 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, you need to 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 of a region.
• A shared, In-use disk can only be attached to servers when the maximum number of servers that the disk can be attached to has not been reached.
• A shared disk can only be attached to servers running the same type of OS (either Windows or Linux).

  For example, if you attach a shared disk to multiple Windows servers and then detach it, the shared disk cannot be attached to Linux servers later. This is because Windows and Linux support different file systems. 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 frozen disk cannot be attached.
• A detached, yearly/monthly system disk purchased together with a server can be re-attached to be used as a data disk for any server. If you want to use it again as a system disk, you need to attach it to the original server.
• A detached, pay-per-use system disk purchased together with a server can be re-attached to be used as a data disk for any server. If you want to use it again as a system disk, you need to 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. In the disk list, locate the disk and click Attach.

   Shared disks support batch attachment, so you can attach a shared disk to multiple servers. In the Attach Disk dialog box, the left area 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 to attach the shared disk. Ensure that the disk and servers are in the same AZ. After you select 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 show up in the drop-down list and cannot be selected.

   Figure 1 Attach Disk
   

5. Click OK.

   A dialog box is displayed, showing "The disk has been attached but still needs to be initialized before it can be used".

6. Click OK to go back 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 ECS details page 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 information about it on the Disks tab.

Follow-Up Operations

• If you are attaching a new disk, you need then log in to the server and initialize the disk before it can be used. To learn how to initialize disks, see Initializing EVS Data Disks.
• If you are attaching an EVS disk with data on it, you do not need to initialize it because initializing the disk will erase the existing data.

  To mount a disk partition on a specific directory of the server, run the following command on the server:

  mount Disk partition Mount point

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?