Usage FAQs

Last updated: 2021-04-19 17:21:13

    What scenarios are cloud disks ideal for?

    • You can purchase and mount elastic cloud disks to use them as data disks when the disk space on your CVM is insufficient.
    • You can purchase and mount elastic cloud disks to use them as data disks when you purchase a CVM without additional data disks.
    • When you have 10 GB of important data stored in an elastic cloud disk on CVM A and need to share the data with CVM B. You can directly unmount the disk from CVM A, and then mount it to CVM B.
    • When a single maximum-sized cloud disk cannot meet your storage requirements, you can purchase multiple cloud disks with equal capacity and configure LVM logical volumes to provide a larger disk capacity.
    • When I/O performance of a single disk cannot meet your business requirements, you can purchase multiple cloud disks and configure RAID 0, RIAD 10, etc., to enhance I/O performance.

    For more information, see Use Cases.

    How do I select a cloud disk?

    Determine your use cases before selecting a disk type.

    • For general use cases including Web/APP applications, logical processing, and small and medium-sized sites, we recommend that you select Premium Cloud Storage as a more cost-efficient solution.
    • For medium-sized databases and image processing users, we recommend SSD for a better performance.
    • For use cases with high requirements for workloads and performance, including large databases, video business, NoSQL, and Elasticsearch, we recommend that you select Enhanced SSD for optimal performance and minimum storage latency.

    What are items I should look out for when using a cloud disk?

    • For an independently purchased cloud disk, use the file system’s UUID or label as the file system ID when configuring the fstab static file system information. This will ensure kernel name consistency of the disk on CVM when any cloud disk is unmounted and remounted.
    • If the cloud disk expires before CVM, the cloud disk will be restricted, unmounted, or even repossessed within a certain period. To prevent business interruption, please take note of the cloud disk’s expiration date and renew it promptly.
    • Consider using the nofail option when configuring fstab if unmounting a cloud disk from your CVM does not severely impact your core business. This prevents the CVM from reporting an error when it restarts after the cloud disk is unmounted.
    • We recommend that you run san policy=OnlineAll in diskpart before using the cloud disk in Windows.
    • When unmounting a cloud disk from Windows, we recommend that you first interrupt all read/write operations on the disk, and perform the offline operation.

    If a custom image and a data disk snapshot is used, how do I automatically mount the data disk when starting a new instance?

    For more information, see the “Automatic Mounting” section in Mounting Cloud Disks.

    How do I purchase a cloud disk?

    You can purchase a cloud disk by creating one via the console or an API. For more information, see Creating Cloud Disks.

    How do I view cloud disk details?

    1. Log in to the CBS console.
    2. At the top of the Cloud Block Storage page, select the region where the disk you want to view resides.
    3. Locate the disk in the list, and view disk information.
      To view more information, click the ID/Name of the disk to enter the details page.

    How do I view the cloud disk usage on the console?

    Cloud Monitor will automatically be enabled once a CVM instance is created. You can view the usage of an initialized cloud disk that is mounted to CVMs by following the steps below:

    1. Log in to the CVM console and access the Instances page.
    2. Select the ID/Name of the target instance to access the details page.
    3. Click on the Monitoring tab to view the instance disk usage.

    What are the most common cloud disk operations?

    For more information, see Operation Overview.

    Why can’t I locate the CVM to which I want to mount a cloud disk?

    Cloud disks cannot be mounted across availability zones. Ensure that the CVM instance you want to use has not been released and that it is in the same region and availability zone as your cloud disk.

    Why am I unable to view the new cloud disk capacity that I mounted to a CVM instance?

    Some Linux CVMs may not recognize an elastic cloud disk. You must first enable the disk hot swapping function in the CVM. For more information, see Enabling the disk hot swapping function.

    After manually mounting a cloud disk, you must perform subsequent operations shown below to make it usable.

    Creation mode Cloud disk capacity Subsequent operations
    Create directly Cloud disk capacity < 2 TB Initializing cloud disks (< 2 TB)
    Cloud disk capacity ≥ 2 TB Initializing cloud disks (≥ 2 TB)
    Create from a snapshot Cloud disk capacity = Snapshot capacity
    • Mounting to a Windows CVM: after logging in to the instance, make the disk online through **Server Management** > **Storage** > **Disk Management**.
    • Mounting to a Linux CVM: after logging in to the instance, run the mount command, such as mount /dev/vdb /mnt.
    Snapshot capacity < Cloud disk capacity ≤ 2 TB
    or
    2 TB < Snapshot capacity < Cloud disk capacity
    Snapshot capacity ≤ 2 TB < Cloud disk capacity

    How do I partition and format a mounted cloud disks?

    For more information, see Initializing Cloud Disks (Smaller than 2TB) or Initializing Cloud Disks (Larger than 2TB).

    What is the relationship between data writing and partition formatting?

    A new data disk or data disk partition must be formatted before use. The disk should also be recorded with the data structure. Formatting the disk establishes a file system on the data disk for data writing. The write-in data size varies by the file systems:

    • For Windows:
      • Quick formatting: assigns the file system only to partitions and rewrites the directory table with little use of your disk capacity.
      • Standard formatting: in addition to the quick formatting tasks, normal formatting scans the partitions sector by sector to identify and mark bad sectors, and fills empty blocks in the cloud disk, which means it essentially writes data to the entire disk. Hence, the capacity of the first snapshot approximates that of the cloud disk.
    • For Linux: after the cloud disk is formatted and before the instance is written with data, the capacity of the first snapshot depends on the format of the disk file system.

    Can the data disk capacity and the system disk capacity be aggregated?

    No. To increase the storage capacity, you need to expand data disk or system disk.

    After expanding my cloud disk, do I need to unmount existing partitions when creating a new independent partition on Linux?

    Yes. To do this, please follow the steps below:

    1. Run the following command to unmount the data disk.
      umount <Mount point>
      
      If the mount point is /data, then run the following command:
      umount /data
      
    2. Unmount the file systems from all partitions on the cloud disk, and perform the subsequent operations. You can run the command again to confirm that the unmounting operation is successful.
      mount | grep '<Disk path>'
      
      If the return is null, then all file systems have been unmounted from partitions on the cloud disk.

    Can multiple CVMs access a cloud disk?

    No. You can mount up to 20 cloud disks to the same CVM, but you cannot mount the same cloud disk to multiple CVMs. You can only share data by unmounting the data disk from CVM A and then mounting it to CVM B.

    How do I identify cloud disks of the same size and type mounted to the same CVM?

    • In Linux, you can view the relationship between the elastic cloud disks and the device name by running the following command:
      ls -l /dev/disk/by-id
      
    • In Windows, you can view the relationship by running the following command:
      wmic diskdrive get caption,deviceid,serialnumber
      
      Or
      wmic path win32_physicalmedia get SerialNumber,Tag
      

    Can I change a CVM system disk from a local disk to a cloud disk?

    Yes. To do this, follow the steps below:

    Note:

    Refer to Creating Custom Images and Creating Snapshots to back up data before performing operations to ensure data security.

    1. Log in to the CVM console and access the Instances page.
    2. Locate the instance of which you want to change the disk, select More > Instance Status > Shutdown under the Operation column to shut down the selected instance.
    3. After the instance is shut down, select More > Resource Adjustment > Change Disk Media Type.
    4. In the pop-up window, select a target cloud disk type, check I have read and agreed to Rules for Changing Disk Media Type, and click Change Now.
    5. Double-check the information, make a payment if applicable, and wait for the process to complete.

      Note:

    Can I unmount the data disk that came with the CVM?

    Since November 2017, data disks purchased with CVMs can be unmounted and remounted. Data disks remounted to CVMs with differing expiration dates might result in lifecycle management issues. We provide various options such as expiration date alignment and auto-renewal configuration for you to better manage data disk lifecycle issues. We recommend you carefully select the appropriate option to avoid data loss caused by disk expiration.

    Why is the separate cloud disk I created released together with my instance?

    When mounting a cloud disk, you can decide if it should be released with the instance automatically. This can be configured via the CBS console or ModifyDiskAttributes API.

    What should I do if I lost my data after restarting my Linux instance?

    Follow the steps below if you lost all data in a directory (such as /data) after restart due to unmount data disk partitions:

    1. Run the fdisk -l command to view the unmounted partitions.
    2. Run the mount /dev/vdb /data command to mount partitions.
    3. Run the df -h command to see if they are mounted successfully.
    4. Complete your automatic mounting configurations. Then cloud disk will be automatically mounted when you start the Linux instance.

    When I unmount a cloud disk, will its data be lost?

    Data in cloud disks will not be modified during mounting or unmounting. To ensure data consistency, we strongly recommend that you follow the steps below:

    • In Linux, log in to the CVM instance and run the umount command on the cloud disk. After the command is executed, log in to the CVM console to unmount the cloud disk.
    • In Windows, stop all read and write operations on all file systems of the cloud disk before unmounting. Otherwise, the data that has not finished being read or written will be lost.

    How do I unmount an elastic cloud disk?

    For more information, see Unmounting Cloud Disks.

    What happens to the system after my cloud disk expires?

    The following instructions are only applicable to elastic cloud disks that support unmounting. Non-elastic cloud disks that do not support unmounting have the same lifecycle as CVMs. For more information, see Overdue Payment.

    • Pay-as-you-go cloud disks:
    • You can continue to use the pay-as-you-go cloud disk for 2 hours from the moment your account balance becomes negative. You will be billed for this period. After 2 hours, the services will be suspended and cloud disk will only store data. Until data is completely deleted, you will still be billed according to the billing standard even if the account balance is negative.
    • If your Tencent Cloud account is topped up to a positive balance within 15 days after the cloud disk has its services suspended, the disk can be restored.
    • If the account balance remains negative for more than 15 days after the cloud disk services are suspended, the pay-as-you-go disk will be repossessed. All data will be erased and cannot be recovered. When your cloud disk is repossessed, the Tencent Cloud account creator and all collaborators will receive a notification via email, SMS, and the console Message Center.

    Please call 4009100100 if you need further information.

    Can I change the cloud disk type after a successful purchase?

    No. However, you can create a snapshot for data backup and then use the snapshot to create a cloud disk of your needed type.

    Can I adjust the cloud disk capacity after a successful purchase?

    Yes. Cloud disks support capacity adjustment. Cloud disk capacity can be expanded, but not reduced.

    Do I have to shut down the CVM instance before a cloud disk expansion?

    No. Please note that you need to assign the expanded capacity to an existing partition, or format it into an independent new partition. Directions on the operating system of the CVM: Extending Partitions and File Systems (Windows) or Extending Partitions and File Systems (Linux).

    What are the requirements for extending the file system?

    Only cloud disks support expansion. Local disks cannot be expanded. For more information, see Cloud Disk Expansion Scenarios.

    Note:

    • We strongly recommend that you create a snapshot before expansion to ensure data security.
    • If the maximum capacity of the cloud disk cannot meet your business needs, please try building up RAID groups or building LVM logical volumes with multiple elastic cloud disks.
    • MBR partition supports disk with a maximum capacity of 2 TB. When you partition disk with a capacity greater than 2 TB, we recommend that you create and mount a new data disk and use the GPT partition format to copy data.

    How do I expand a cloud disk?

    For more information about expansion operations, see Cloud Disk Expansion Scenarios.

    Why does the capacity seem unchanged after I expanded my data disk?

    The expansion on the console only increases the storage capacity of the data disk. You also need to log in to your CVM instance and extend the partitions and file systems. For more information, see:

    Do CVMs support CPU/memory expansion?

    If the system disk of the CVM is a cloud disk, you can adjust its CPU and memory.

    What should I do if the cloud disk is partitioned in MBR format and cannot be expanded?

    MBR partition supports disk with a maximum capacity of 2 TB. When you partition disk with a capacity greater than 2 TB, we recommend that you create and mount a new data disk and use the GPT partition format to copy data.

    What should I do if a cloud disk cannot meet my business requirements even at its maximum capacity?

    We recommend you build up RAID groups or build LVM logical volumes with multiple elastic cloud disks.

    How do I build up a RAID group by using multiple elastic cloud disks?

    For more information, see Building Up RAID Groups.

    How do I build LVM logical volumes by using multiple elastic cloud disks?

    For more information, see Building LVM Logic Volumes with Multiple Elastic Cloud Disks.

    How do I export the data from a cloud disk?

    You can use FTP to upload and download data. For more information, see Building the FTP Service (Windows) and Building the FTP Service (Linux).

    What happens to the data when a CVM is terminated?

    • The lifecycle of a system disk is the same as that of the CVM. When the CVM is terminated, the data stored in the system disk will also be terminated.
    • The lifecycle of a data disk (that is, an elastic cloud disk) is independent from that of a CVM. You can decide if an elastic cloud disk and its data will be retained after a CVM expires.

    Therefore, we recommend that you use elastic cloud disks to store data that needs to be saved for a long term.

    How can cloud disks be recovered after being formatted?

    Cloud disks cannot be recovered after being formatted. We recommend that you create a snapshot before formatting.

    How do I delete a cloud disk?

    • The lifecycle of a system disk is the same as the CVM. It can only be deleted when the CVM instance is terminated.
    • The lifecycle of a data disk (that is, an elastic cloud disk) is independent from that of the CVM. It can be deleted separately. For more information, see Terminating cloud disks.

    Can my system disk be partitioned?

    No.

    How do I update the mounting information at the mount point?

    LinuxOS supports the systemd mount command which will generate a mounting configuration file on top of the existing .mount file. Mounting to the same directory /run/systemd/generator/ will be affected by this command.

    Issue

    Assume you have mounted the data disk vdb to the directory /opt/apps (run the mount -a command on the fstab file based on disk uuid). Now, you want to mount a new data disk vdc to the same directory and replace the old one. If you directly mount vdc to the directory, you will not be able to read the data.

    Solution

    1. Delete the configuration of the corresponding mount point (for example, run the rm /run/systemd/generator/opt-apps.mount command).
    2. Run the reload command (for example, use systemctl daemon-reload).
    3. Mount the data disk (for example, run the mount /dev/vdc /opt/apps command).