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CDS

  • API Reference
    • Disk Related Interfaces
  • Dedicated Cluster Operation Guide
    • Charge
    • Create a dedicated cluster
    • Create Cloud Disk Server in Dedicated Cluster
    • Expand Dedicated Cluster
    • View Dedicated Cluster Information
    • What Is a Dedicated Cluster
  • Disk Operation Guide
    • Basic Operations
      • Create cloud disks
      • Disk encryption
        • Encrypt Data Disk and Snapshot
        • Encrypt System Disk and Image
        • Encryption Overview
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        • Format Disk Partition on Linux System
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      • Monitor alarm
      • mount Cloud Disk Server
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        • Use Performance Pre-Configuration
        • What Is Performance Pre-Configuration
      • Resize cloud disks
        • Expansion Overview
        • Extend Disk Partition on Linux Data Disk
        • Extend Disk Partition on Linux System Disk
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Table of contents on this page
  • How to resolve the drive letter drift issue of a CDS cloud disk?
  • How to conduct regular and comprehensive checks on the configuration and usage status of a CDS cloud disk?
  • A new CDS cloud disk has been purchased, but it cannot be seen in the server. What should I do?
  • I selected the wrong disk type and want to upgrade the current general-purpose HDD to a high-performance cloud disk. How to operate?
  • Can data from a general-purpose HDD be migrated to a high-performance cloud disk?
  • How to migrate data in a CDS cloud disk?
  • How to expand the capacity of a local disk?
  • How to properly take a CDS cloud disk offline?
  • How to mount and use a CDS cloud disk in a Windows system?
  • Can a snapshot exist independently of a CDS cloud disk?
  • Is it necessary to unmount a disk before creating a disk snapshot?
  • When a separately purchased CDS cloud disk is mounted to a virtual machine with a Windows operating system, can it have an independent drive letter in the system? Is the usage method of the disk in the Windows system exactly the same as that of a local disk?
  • Can a CDS cloud disk already mounted to a virtual machine be unmounted and then mounted to another virtual machine? Can it be unmounted again later and mounted back to the original virtual machine? Can data be imported from one virtual machine to another through the “unmount and remount” method?
  • Can a CDS cloud disk be mounted shared among multiple BCC cloud servers?
  • In a Linux server, how to install a website on a data disk?

Configuration-related questions

Updated at：2025-11-03

How to resolve the drive letter drift issue of a CDS cloud disk?

After mounting/unmounting operations, CDS cloud disks often experience drive letter drift. You can query the disk’s drive letter using the command: grep . /sys/block/vd*/serial. The drive letter obtained via this command is not affected by disk mounting/unmounting operations and remains fixed.

How to conduct regular and comprehensive checks on the configuration and usage status of a CDS cloud disk?

You can activate the "Cloud Advisor" service to regularly receive inspection reports on the security, availability, performance and cost of cloud resources. The report includes several CDS-related check items, such as: CDS - Cloud disk deactivated, CDS - Low utilization rate, CDS - Abnormal throughput, CDS - Unmounted cloud disks, CDS - Snapshot validity, CDS - Automatic snapshot policy, CDS - High utilization rate, etc. Please visit Cloud Advisor Homepage to learn about or activate the Cloud Advisor service.

A new CDS cloud disk has been purchased, but it cannot be seen in the server. What should I do?

If a newly purchased BCC disk is mounted via the console but not visible in the virtual machine, the issue arises because the CDS cloud disk has not been formatted. After purchasing a new CDS cloud disk, you first need to perform the [mounting operation](CDS/Disk Operation Guide/Basic Operations/mount Cloud Disk Server.md) on the disk. After mounting, you must also complete the disk formatting process before the disk can be used normally. For details, refer to Format Disk.

Note: Formatting will erase all data. If the CDS contains important data, please ensure to back it up beforehand.

I selected the wrong disk type and want to upgrade the current general-purpose HDD to a high-performance cloud disk. How to operate?

You can perform “capacity expansion and reconfiguration” operations on purchased disks via the console or API. Currently, capacity expansion is supported for both prepaid and postpaid CDS cloud disks that have been purchased. Additionally, for purchased prepaid cloud disks, type upgrades are supported; for purchased postpaid cloud disks, both type upgrades and downgrades are supported. For details, please refer to Online CDS Disk Type Change.

Can data from a general-purpose HDD be migrated to a high-performance cloud disk?

Yes. You can migrate data in two ways. Create a snapshot of the data in the general-purpose HDD, then create a new CDS cloud disk from this snapshot. When creating the new disk from the snapshot, you can configure the new disk’s type as a high-performance cloud disk. Or, directly change the disk type from general-purpose HDD to high-performance cloud disk via the console or API. For details, please refer to Online CDS Disk Type Change.

How to migrate data in a CDS cloud disk?

If the disk data you want to migrate is under the same account:

  • If you want to migrate system disk data, for servers in the same region (e.g., both in North China - Beijing / South China - Guangzhou regions), data can be transferred by creating a custom image and selecting the previously created custom image when installing the system on the new server;
  • To migrate data disk data to the same availability zone in the same region (e.g., the current disk is in availability zone A of North China - Beijing, and you want to migrate it to the same availability zone in the same region): You can directly mount the cloud disk to be migrated to the new server. (Alternatively, you can create a snapshot of the disk and then create a new CDS cloud disk from the snapshot to complete the migration.) To migrate to another availability zone in the same region, you can copy the data by creating a snapshot of the CDS disk. Then, create a new CDS cloud disk from this snapshot in the target availability zone and mount it to the new server for use. To migrate data disk data to another region, you can complete the migration using the Cross-Region Snapshot Replication feature;

If the disk data you want to migrate is under different accounts:

  • If you want to migrate system disk data: You can use Shared Images to achieve fast migration of system disk data for BCC cloud servers and environment deployment across accounts in the same region;
  • Other migrations, such as CDS data cross-account/cross-region (e.g., Beijing - Guangzhou region) migration, temporary data disk data migration, and system disk data cross-region (e.g., Beijing - Guangzhou region) migration, can currently only be performed manually through offline data copying;

How to expand the capacity of a local disk?

BCC servers allow capacity expansion for system disks and data disks of the CDS cloud disk type. At present, expansion of non-CDS disks (including local disks) is not supported. If you're planning to extend the capacity of a disk, it’s strongly recommended to create a snapshot in advance to protect against data loss caused by errors.

Note: Currently, CDS cloud disks support online capacity expansion. After completing the expansion, you also need to reconfigure the file system of the expanded cloud disk. For detailed operations, please refer to CDS Disk Capacity Expansion.

How to properly take a CDS cloud disk offline?

First unmount it from the server internally. For Linux systems: Execute the umount command for the disk; For Windows systems: Set the disk to offline mode. Then, unmount it via the console page. For specific operations, please refer to [Detach CDS Disk](CDS/Disk Operation Guide/Basic Operations/Unmount Cloud Disk Server.md).

How to mount and use a CDS cloud disk in a Windows system?

On Windows servers, the data disk is offline by default and needs to be manually brought online before use.

  • For Windows 2012: Go to Server Manager > File and Storage Services > Volumes > Disks, then set the offline disk to online mode;
  • For Windows 2008: Go to Server Manager > Storage > Disk Management, then set the offline disk to online mode;

Can a snapshot exist independently of a CDS cloud disk?

A snapshot is generated based on the data of a specific disk, so creating a snapshot requires the presence of a disk first. However, when releasing a CDS cloud disk, you can opt to retain the snapshot data created from the disk. This way, although a disk is necessary for snapshot creation, the snapshot can be preserved even after the disk is released.

Is it necessary to unmount a disk before creating a disk snapshot?

No, it's not mandatory. Snapshots can be created for a disk in “Mounted,” “Unmounted,” or “Detached” status. However, for a complete snapshot of the disk's data, it is recommended to unmount the CDS cloud disk first or ensure that no data-writing operations occur during the snapshot creation process.

When a separately purchased CDS cloud disk is mounted to a virtual machine with a Windows operating system, can it have an independent drive letter in the system? Is the usage method of the disk in the Windows system exactly the same as that of a local disk?

Yes.

Can a CDS cloud disk already mounted to a virtual machine be unmounted and then mounted to another virtual machine? Can it be unmounted again later and mounted back to the original virtual machine? Can data be imported from one virtual machine to another through the “unmount and remount” method?

All of the listed scenarios are supported.

Can a CDS cloud disk be mounted shared among multiple BCC cloud servers?

A single CDS cloud disk can only be mounted to one BCC cloud server at a time and cannot be shared with multiple BCC servers simultaneously.

In a Linux server, how to install a website on a data disk?

The website directory is the custom path you initially define, which varies based on your web configuration. You need to set it up according to the specific configuration file of the relevant web service.

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