You can mount an elastic cloud disk (used as a data disk for the CVM) to any CVM in the same availability zone. Each CVM can have up to 20 data disks mounted to it. You can use the following methods to mount a cloud disk.

• When launching a new CVM, specify the corresponding custom image and data disk snapshot.
  After automatic mounting, reads and writes on the data disk can be directly performed without disk initialization operations such as partitioning and formatting.

• For an independently purchased cloud disk, the elastic cloud disk can be manually mounted to an existing CVM instance in the same availability zone through the console or API.

  • Directly created cloud disks
    After manual mounting, you need to perform initialization operations on the disk such as partitioning and formatting. For more information, see Initializing cloud disks (smaller than 2TB) or Initializing cloud disks (larger than or equal to 2TB).
  • Creating a cloud disk from a snapshot
    If the capacity of the cloud disk is equal to the capacity of the snapshot, reads and writes on the data disk can be directly performed without disk initialization operations such as partitioning and formatting.
    If the capacity of the cloud disk is larger than the snapshot capacity, you need to extend the file system or convert the partition format.

  Some Linux CVMs may not recognize elastic cloud disks. You can first enable the disk hot swapping function on the CVM. For details, see Enable disk hot swapping function.

Automatic Mounting

Mounting data disks (Windows)

If you use a custom image to create a Windows CVM instance, the cloud disk created from the corresponding data disk snapshot will be automatically mounted. The custom image in use and the data disk snapshot must meet the following requirements:

• The data disk must be formatted as ntfs or fat32 before you create a snapshot.
• The SAN policy in the custom image is onlineAll.

  Public images for Windows that are currently provided by Tencent Cloud have been configured by default, but we still recommend that you check the configuration before creating any custom images by following the steps below:
  

Mounting data disks (Linux)

If you use a custom image to create a Linux CVM instance, the cloud disk created from the corresponding data disk snapshot will be automatically mounted. The custom image in use and the data disk snapshot must meet the following requirements:

• The data disk must be formatted before the snapshot is created. That is, the data disk has been successfully mounted to the original CVM.
• For the system disk to create a custom image, you need to add the following commands to the file /etc/rc.local to write the data disk mounting point to the file.

  mkdir -p <mount-point>
  mount <device-id> <mount-point>

  The parameter descriptions for these commands are as follows:
  • <mount-point> must be set to the mounting point of the file system, such as /mydata.
  • <device-id> must be set to the actual file partition location. For example, enter /dev/vdb when there is no partition in the file system, and /dev/vdb1 when there is a partition in the file system.

Mounting Manually

Using the console to mount cloud disks

1. Log in to the CBS Console.
2. On the cloud disk list page, you can mount cloud disks using the following methods:
   a. Click More>Mount in the row of the cloud disk with the status To Be Mounted.
   b. Select the cloud disks with the status To Be Mounted, and click Mount at the top of the cloud disk list to perform batch mounting.
3. In the pop-up box, click OK.
4. Refresh the cloud disk list.
   If the status of the cloud disk changes to Mounted, this indicates that mounting is successful.
5. Depending on the cloud disks, you need to choose to perform the corresponding subsequent operations to make the cloud disk available.

   Creation Mode	Cloud disk capacity	Subsequent Operations
   Create directly	Cloud disk capacity< 2TB	Initializing cloud disks (smaller than 2TB)
   	Cloud disk capacity ≥ 2TB	Initializing cloud disks (larger than or equal to 2TB)
   Create from a snapshot	Cloud disk capacity = snapshot capacity	Mounting to a Windows CVM: log in to the instance and choose **Server Management** -> **Storage** -> **Disk Management** to associate it with a CVM. Mounting to a Linux CVM: log in to the CVM instance and run the `mount ` command, such as `mount /dev/vdb /mnt`.
   	Snapshot capacity < cloud disk capacity ≤ 2TB or 2TB < snapshot capacity < cloud disk capacity	Mounting to a Windows CVM: Expanding partitions and file systems (Windows) Mounting to a Linux CVM: Expanding partitions and file systems (Linux)
   	Snapshot capacity ≤ 2TB < cloud disk capacity	If MBR partition format is used in the snapshot: Refer to Initializing cloud disks (larger than or equal to 2TB)Using GPT to re-partition:This operation will delete the original data If GPT partition format is used in the snapshot: Mounting to a Windows CVM: Expanding partitions and file systems (Windows) Mounting to a Linux CVM: Expanding partitions and file systems (Linux)

Using the API to mount cloud disks

You can use the AttachDisks API to mount a cloud disk. For more information, see Mounting cloud disks.

Enabling the disk hot swapping function

All images that are currently provided already support the mounting and unmounting operations of elastic cloud disks. To unmount a cloud disk, you must first execute the umount (Linux) or offline (Windows) operations. Otherwise, the CVM may not recognize the elastic cloud disk next time it is mounted.
However, if you have previously purchased a CVM with one of the following operating systems and plan to mount it with elastic cloud disks, we recommend that you first add the related driver to the CVM to get the hot swapping function:

1. As the root user, Log In to the Linux CVM.
2. Execute the following command to add the driver.

   modprobe acpiphp

   If you need to load the acpiphp module when shutting down or re-starting the CVM, we recommend you execute Step 3 to set the acpiphp module to load automatically when starting up.
   

3. (Optional) According to the different operating systems, select the related operation method to set the acpiphp module to load automatically when starting up:
   • CentOS 5 Series
     a. Execute the following command to create and open an acpiphp.modulesfile.

     vi /etc/sysconfig/modules/acpiphp.modules

     b. Add the following content to the file, and save.

     #!/bin/bash
     modprobe acpiphp >& /dev/null

     c. Execute the following command to add execution permissions.

     chmod a+x /etc/sysconfig/modules/acpiphp.modules

   • Debian 6 Series, Ubuntu 10.04 Series
     a. Execute the following command to modify the file.

     vi /etc/modules

     b. Add the following content to the file, and save.

     acpiphp

   • openSUSE 12.3 Series
     a. Execute the following command to modify the file.

     vi /etc/sysconfig/kernel

     b. Add the following content to the file, and save.

     MODULES_LOADED_ON_BOOT="acpiphp"