Help Center/ Elastic Volume Service/ User Guide/ Managing EVS Snapshots/ Using EVS Snapshots/ Creating a Disk from a Snapshot
Updated on 2026-09-23 GMT+08:00
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Creating a Disk from a Snapshot

Scenarios

When you create a disk from a snapshot, the new disk contains the same data as the snapshot. This enables you to copy data between disks within the same AZ or across AZs for purposes such as environment cloning or data backup. This section describes how to create a new data disk from a snapshot.

Background

Disks created from snapshots use lazy loading. They can be attached and used immediately after creation without waiting for all snapshot data to finish loading. Snapshot data is loaded into the new disk in the background as needed. After loading is complete, the disk delivers the same performance as a newly purchased disk of the same type.

Customer impact during lazy loading:

  • Read/write performance impact

    First read (data not yet loaded): When data is accessed for the first time, the system reads it directly from snapshot storage, which results in higher latency than the disk's rated performance. Subsequent reads of the same data blocks return to normal performance.

    First write (data not yet loaded): When writing to an unloaded data block, the system must first load the corresponding snapshot data before completing the write, which may increase initial write latency. Write performance for already loaded or previously written data blocks is not affected.

    Data loading completed: The disk provides the same read/write performance as a newly purchased disk of the same type. Lazy loading does not affect the disk's final performance or capacity.

  • Typical impact scenarios

    During data loading, workloads involving large-scale random first-time reads or writes, such as full database scans, batch file copies, or batch data loading during application cold starts, may experience higher I/O latency and lower throughput, resulting in slower response times.

    Before loading completes, measured disk performance may be lower than the IOPS and throughput limits displayed on the purchase page. Performance benchmarking is not recommended during this period because results may not reflect steady-state performance.

    Lazy loading does not affect data integrity or correctness, and does not prevent operations such as disk attachment, partition creation, or file system mounting.

Usage recommendations:

  • For performance-sensitive workloads, perform a full read after disk creation to trigger data loading before using the disk in production. For example, run dd if=/dev/vdX of=/dev/null bs=1M to sequentially read the entire disk.
  • For workloads that need to go into production immediately, create disks from snapshots during off-peak hours and allow sufficient time for data loading to complete.
  • Do not interpret higher read/write latency during lazy loading as a disk failure or a performance issue. If performance problems persist after loading completes, contact technical support.

Constraints

Table 1 Constraints

Item

Description

Legacy snapshots
  • Batch disk creation from a snapshot is not supported.
  • A disk created from a snapshot has the same device type (SCSI or VBD), encryption attribute, AZ, region, and disk type as the snapshot's source disk.
  • A snapshot whose name starts with autobk_snapshot_vbs_, manualbk_snapshot_vbs_, autobk_snapshot_csbs_, or manualbk_snapshot_csbs_ is automatically generated during backup. Such a snapshot can only be viewed. It cannot be used to create new disks.

Standard snapshots
  • A standard snapshot with Instant Snapshot Restore disabled can only be used to create disks when the snapshot status is Available.
  • If Instant Snapshot Restore is enabled for a standard snapshot, when its upload is in progress, you can use it to create a disk but cannot change the device type (SCSI or VBD), encryption attribute, AZ, and type of the new disk. They are kept the same as those of the snapshot's source disk.
  • You can use a standard snapshot to batch create disks after its data upload is complete.
  • After a standard snapshot has been uploaded, you can change the device type (SCSI or VBD), encryption attribute, AZ, or type of the disks when using this snapshot to create disks on the console or through the V5 version API. Snapshots created using the V2 version API cannot be used across AZs.

General constraints
  • When you create a disk from a snapshot, the disk capacity must be greater than or equal to the snapshot size. If you do not specify a disk capacity, the default capacity of 10 GiB is used when the snapshot size is smaller than 10 GiB. If the snapshot size exceeds 10 GiB, the snapshot size is used as the disk capacity.

You can view the snapshot upload progress in the status column. If there is a progress bar, the upload is still in progress. After the progress bar disappears, the upload is complete.

Creating a Disk from a Snapshot on the Snapshots Page

  1. Sign in to the EVS console.
  2. Click in the upper left corner and select a region.
  3. In the navigation pane on the left, choose Elastic Volume Service > Snapshots.

    The Snapshots page is displayed.

  4. In the snapshot list, locate the target snapshot and click Create Disk in the Operation column.
  5. Configure the disk parameters. For details, see parameter descriptions and operations provided in Purchasing an EVS Disk.

    To specify a disk capacity larger than the snapshot size, simply enter your desired capacity in the Disk Specifications area.

  6. Click Next.
  7. Confirm the configuration and click Submit.
  8. If you are buying a yearly/monthly disk, make the payment and click OK.

    The disk list page is displayed.

  9. After the disk is purchased, view the new disk in the disk list.

    When the disk status changes to Available, the disk is successfully created.

When a disk status changes to Available, the disk can be attached and used normally. However, snapshot data may still be loading in the background due to lazy loading. Available does not mean that all data has been loaded. Before all data is loaded, first-time access to unloaded data blocks will experience higher read/write latency than the disk's rated performance. For details, see Lazy Loading Impact.

Creating a Disk from a Snapshot When Purchasing the Disk

When purchasing a disk, you can select Snapshot for Data Source Type and select a source snapshot. For details, see Purchasing an EVS Disk.

Figure 1 Creating disks from a snapshot

Follow-Up Operations

A disk created from a snapshot already has partitions and file systems. You need to attach the disk to an ECS and then mount the partitions before you can use the disk.
  • If you choose not to attach the disk to a server during creation, attach it to an ECS by referring to Attaching an EVS Disk before using it.
  • If you choose to use existing partitions instead of re-initializing the disk, mount the partitions in the OS.
  • If you choose to re-initialize the disk, do as follows:

    Note that re-partitioning a disk will erase all the existing data on the disk, so you are advised to use snapshots to back up the disk data first.

    • In Linux, unmount the partitions, delete them (by running fdisk <disk-name>, entering d and the partition number, and entering w), and then re-initialize the disk.
    • In Windows, delete the partitions (using the volume deletion tool) and then re-initialize the disk.

    For details about how to initialize a disk, see Initializing EVS Data Disks.

    File system mounting, partition checks, and other operations are not affected by lazy loading. However, the first access to file data triggers on-demand snapshot loading, which may temporarily increase application response times after mounting. Performance returns to normal once loading completes.

Helpful Links

Parent Topic: Using EVS Snapshots