Meaning and difference of AliCloud image and AliCloud snapshot

AliCloud image The service can install the operating system and data backup for Alibaba Cloud ECS servers. AliCloud Snapshot A service is a backup file of data status at a point in time of the ECS, which is used to back up data, create custom images, and apply disaster tolerance. AliCloud images and snapshots can both be used to back up server data, but they also have certain intersections. No matter novice, Xiaobai or veteran, it is easy to confuse these two concepts. Today, Lao Wei will explain them in detail.

AliCloud image service

Alibaba Cloud ECS images provide the information needed to create ECS servers. For example, the process of installing the operating system using the Windows installation file is similar to that of installing the operating system. When we are Create ECS server on AliCloud website To install the operating system from the image file, first select the image.

AliCloud images are divided into public images, custom images, shared images, and image market images according to their sources.

• Public image: A genuine licensed system image officially provided by Alibaba Cloud, which is highly secure and stable. The public images provided by AliCloud include mainstream Windows Server system images and Linux system images. For more details, see Public image ；
• Custom image: an image created using ECS or snapshots, or a custom image imported locally by users. This is where the snapshot intersects. For more details, see Custom Image 。 Custom images are applicable to many scenarios, such as multiple server operating systems with the same production environment need to be pre installed, disaster recovery across regional nodes, and snapshot batch deployment as a redundant backend. It is applied to the old and new servers to move;
• Shared image: the image shared to you by other AliCloud accounts. For more details, see Shared Image ；
• Image market image: according to different suppliers, the image of the image market includes images provided by Alibaba Cloud official accounts and images provided by third-party service providers authorized by Alibaba Cloud · Cloud Market. Images in the image market include operating systems and pre installed software, and are strictly tested to ensure the security of image content. However, in the actual use of Old Wei, there are many duplicate images. For example, the pagoda panel is provided by many different businesses, and there are many new and old versions. It is recommended to choose the version provided by the pagoda official. For more details, see Mirror market ；

Alibaba Cloud image application scenarios

Most are used for initial installation of the operating system after the creation of the ECS, or for rapid migration when the website moves.

Alibaba Cloud Snapshot Service

Snapshot is a backup service for data status at a certain point in time on Alibaba Cloud ECS servers. It is used to back up data, apply disaster recovery, and create custom images. As Lao Wei understands, AliCloud snapshots are equivalent to ghost backups we make for computers. Back up the state when the operating system was just installed (or the best state you think). After the system crashes, it can be quickly recovered without affecting the use.

AliCloud snapshots are the same as ghost backup packages. Multiple snapshots can be saved to facilitate later recovery of backup files by point in time. The first snapshot of cloud disk is a snapshot of all data actually used, but does not back up empty data blocks. Subsequent snapshots are incremental snapshots that only store changed data blocks.

Alibaba Cloud snapshot application scenarios

• Disaster recovery backup: backup data on a regular or temporary basis (daily, weekly, monthly, before installing system programs, and before expansion). To ensure the online rate of the system, create snapshots for the cloud disk to achieve local and remote disaster recovery;
• Environment replication: create a custom image when the application moves, store snapshots and replace data disks. Then create ECS instances on the new server using custom images to achieve rapid environment replication;
• Improve fault tolerance: including but not limited to timely rollback data in case of errors in the above operations, reduce operational risk, realize application version rollback, and ensure stable online application services;
• Snapshots are copied from one region to another region, and another region will create a snapshot copy;
• See more scenarios ECS Document>Snapshot

Differences between AliCloud images and AliCloud snapshots

• The image can directly create ECS servers, but not snapshots;
• The image can restore ECS data across regions by copying the image, and snapshots cannot cross regions;
• Snapshots can be data backups of ECS server system disks or data disks, while images are data of ECS server system disks;
• Snapshots are suitable for backing up cloud disk data, and images are suitable for creating one or more new ECS servers (such as the above mentioned batch initial installation of server systems using custom images);

Mr. Wei listed the application scenarios of AliCloud snapshots and custom images to further explain the differences between the two.

Alibaba Cloud snapshot application scenarios

• Regular data backup, which automatically executes the snapshot strategy daily, weekly or monthly to back up data according to the set cycle;
• Temporary data backup, such as system updates, application releases and other temporary changes to the system, manually create snapshots in advance to back up the system;
• Create snapshot backup data before system disk expansion;
• Disk data migration: create a snapshot for the disk, and use the disk as the basic data of another disk;

Custom image application scenarios

• Backup systems that will not be changed in the short term, such as application systems that have been released or updated;
• Use the installed and configured system as the template to create new ECS instances for batch deployment applications;
• System and data migration: migrate ECS servers from classic networks to VPC networks;
• Restore systems across zones and regions;

Association of snapshots and mirrors

• When you use the server to create a custom image, ECS creates a snapshot for each cloud disk of the ECS, that is, the custom image contains snapshots of all cloud disks of the ECS server. See Creating custom images using ECS servers ；
• Using system disk snapshots, you can also create custom images. See Create a custom image using snapshots ；

Lao Wei's comments

about AliCloud Snapshot and AliCloud image The meaning, usage scenarios, and differences are basically those mentioned above. To put it simply, if you want to toss the system around, use snapshots to back it up first; If you want to move, use a custom image. If you want to know how to use snapshots and custom images for system backup, you can check Alibaba Cloud official documents 。