Snapshots

Last updated: 2020-06-28 10:22:11

    Is snapshot available in all availability zones?

    Yes.

    Will creating a snapshot affect the disk performance?

    Creating a snapshot will occupy a small amount of the cloud disk I/O. We recommend creating snapshots when business is slow.

    How long does it take to create a snapshot?

    The time it takes to create a snapshot is influenced by factors such as the number of disk writes and the underlying read-write operations. Creating a snapshot will not affect your disk use.

    Do I need to shut down the CVM to roll back snapshots?

    • For a cloud disk that has been mounted to a CVM, you have to shut down the CVM to roll back snapshots.
    • For a cloud disk that has not been mounted, you can directly roll back snapshots.

    How is the size of the first full snapshot of a cloud disk calculated?

    The first snapshot created on a cloud disk is a full snapshot that copies all the data of the cloud disk at a point in time. The snapshot size equals the used capacity of the cloud disk. For example, if the total capacity of a cloud disk is 200 GB and 122 GB have been used, the size of the first full snapshot is 122 GB.

    Can I download or export CVM instance snapshots to a local device?

    No. Snapshots cannot be downloaded or exported to local devices. You need to create a custom image from a snapshot and then export the image.

    Do automatic snapshots differ from or conflict with manual snapshots?

    No. You can use both of them at the same time. However, you cannot create manual snapshots while automatic snapshots are being created.

    • You cannot create a custom disk snapshot until the automatic disk snapshot has finished being created, and vice versa.
    • If one snapshot created from a large disk lasts longer than the interval between two automatic snapshots, the next automatic snapshot will be skipped. For example, if you configure the automatic snapshots to be created at 9:00, 10:00, and 11:00 and the automatic snapshot created at 9:00 lasts for 70 minutes and ends at 10:10, the next automatic snapshot will be created at 11:00 and not at 10:00.

    Can I create snapshots for local disks?

    No. We recommend that you use data redundancy at the application layer or create deployment sets for clusters to improve the availability of applications.

    After I release the cloud disk, will local snapshots be deleted?

    No. You need to delete snapshots via the Console or APIs. For more information, see Deleting Snapshots.

    Why does the used disk capacity displayed in the file system differ from the snapshot size?

    A cloud disk snapshot is a block-level clone or backup. In general, the snapshot capacity will be larger than the data capacity displayed in the file system because:

    • The underlying data block stores the metadata of the file system.
    • Some data are deleted. Deleting data modifies the written-in data block, which will be backed up to snapshots.

    How can I prevent snapshots from being deleted by Tencent Cloud?

    • Manual snapshots: Tencent Cloud will never delete them, regardless of whether their corresponding disk or instance has been released.
    • Scheduled snapshots: you can set the retention period of scheduled snapshots to long-term retention to prevent them from being deleted. This way, only the snapshot created earliest will be deleted when the snapshot quota is reached. For detailed directions, see Use Limits.

    How can I delete snapshots to reduce backup costs?

    • For cloud disk snapshots, you can delete them directly via the Console or APIs. For more information, see Deleting Snapshots.
    • For snapshots associated with custom images, you must first delete the custom images and then delete the snapshots.

    Will automatic snapshots be deleted after the instance expires or the cloud disk is released?

    No. Automatic snapshots will not be deleted after the instance expires or the cloud disk is released because they are retained based on the retention period policies of scheduled snapshots.

    How can I delete snapshots from which an image or cloud disk was created?

    • Snapshots from which a cloud disk was created: you can delete the snapshots separately. After you delete a snapshot, you will not be able to operate a business that depends on the original snapshot data.
    • Snapshots from which a custom image was created: you have to first delete the image and then delete the snapshots.
    • Snapshots from which an instance was created: you can delete the snapshots separately. After you delete a snapshot, you will not be able to operate a business that depends on the original snapshot data.

    Will the snapshot policy fail to be executed if I create a custom image or cloud disk based on the scheduled snapshot?

    No.

    Can a cloud disk have multiple automatic snapshot policies?

    No.

    How can I prevent data loss caused by incorrect operations?

    You can create snapshots to back up data before you perform risky operations. For example, you can create a snapshot before you modify critical system files, migrate instances from a classic network to a VPC, back up data, restore an instance that was released accidentally, prevent network attacks, change operating systems, or provide data support for a production environment. For more information, see Creating Snapshots. If an error occurs, you can roll back snapshots to reduce risks.

    I created an instance in the Guangzhou region and created snapshots for the data disks of the instance. After the instance expired and was released, I purchased another instance in the Guangzhou region. Can I roll back the snapshots on the new instance to restore the original instance?

    No. Snapshots can only be rolled back to the cloud disk in which they are created. You can use the snapshots of the previous data disk to create a cloud disk and mount the cloud disk to the new instance. For more information, see Creating Cloud Disks Using Snapshots and Mounting Cloud Disks.

    What are the differences between snapshots and images?

    If no data disk is mounted to an instance and all data is written on the system disk, the data on the system disk cannot be protected by creating an image. Images cannot be scheduled for continuous backup. Once the system disk data is damaged, you can only recover the data to the state when the image was initially created. Therefore, images are not suitable for data protection. Specific differences are as follows:

    Name Snapshots Images
    Characteristics Backup data of a cloud disk at a certain point in time CVM software configuration template, which contains information about the operating system and pre-installed programs
    Use Cases
    • Regularly back up important business data
    • Back up data before major operations
    • Produce multiple copies of data
    • Back up systems that will remain unchanged in the short term
    • Deploy applications in batches
    • Migrate the system

    How can I migrate snapshot data from account A to account B?

    Snapshots cannot be migrated. Instead, you can create an image from the snapshot that you want to migrate and share the image with another account.

    Can I create a custom image from data disk snapshots?

    No. You can only create a custom image from system disk snapshots.

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