General information about cloud server network disk backups
You can backup cloud server network disks in two ways:
- configure automatic scheduled backups. Create a backup plan, specify a backup schedule, and add network disks to the plan — see Configuring scheduled backups for details. You can configure scheduled full or incremental backups;
- manually — commit the system state and store the backup remotely from the disk. To create a backup manually, you do not need to configure the plan — see the Create a backup manually subsection for details. Only a full backup can be created manually.
The service is powered by OpenStack Karbor and Cinder components.
To see alternative ways to back up cloud servers, see the Backup Methods table.
Full backup
A full backup is a complete backup of the disk with all data.
Full backups can be created automatically on a schedule and manually.
You can configure a schedule for creating full backups by day of the week or via cron-expression. The plan settings specify how many recent backups to keep.
Incremental backup
An incremental backup is a copy of the changes between the current disk state and the previous backup created as planned. This backup is faster than a full backup and takes up less space because it stores only the changes on the disk.
Incremental backups can only be created automatically on a schedule.
Incremental backups are created daily at the time specified in the backup plan settings. A full backup is created first, and then it is created once a week. Incremental backups are created on the remaining days.
Creating backups
We guarantee the consistency of the copies at the crash-consistency level. At the moment of creation, the data that is on the disk is written to the backup. Also "dirty data", which appears when files on the disk are overwritten or deleted, can be written to the backup. Data in the cloud server's memory is not written to the backup. Because of "dirty data", the size of a full backup may exceed the actual amount of data and files on the disk; an incremental backup may exceed the difference between the current amount of data and the size of the previous backup.
Backup creation does not affect the performance of the cloud server — all operations take place on Selectel's computing power. When creating a full backup, an instantaneous snapshot of the disk is created, so there is no load growth on the cloud server. When creating an incremental backup, changes between the current disk state and the previous backup are calculated on the fly, and the difference between the states is transferred to the backup store.
Backup storage
Full and incremental backups are stored in Ceph storage — a cluster is deployed in each pool segment. Both backups and disks are stored in the same cluster, thus increasing the speed of backup creation and recovery from it.
The backups are stored on separate servers in three copies — this will preserve the data if there is a problem with the servers where the disks reside.
The backup cannot be downloaded, but you can recover the disk from it — a new disk of the same type and size as the original will be created.
Backups that are automatically created on a schedule are stored in chains of seven — one full backup and six subsequent incremental backups. The plan specifies how many full backups to store (at least two). For example, if the plan settings specify storing three full backups, the last three backup chains will be stored.
Backup storage limitations
If backups are created automatically on a schedule, the total number of backups in one project is unlimited. However, there is a limit of 90 backups for full backup plans and 14 full backups and 78 incremental backups for incremental plans.
A maximum of 1000 manually created backups can be stored in one project.
Automatic deletion of backups
Only for backups that are created automatically on a schedule.
In the plan settings, when you choose to store recent backups, you specify how many recent full backups or chains of incremental backups to store.When a new full backup is created for a disk, the service checks the total number of full backups of the disk within one plan.If this number is greater than the maximum number specified in the plan, the oldest full backups are deleted.
Incremental backups are stored in chains of seven backups — one full backup and six subsequent incremental backups.One week after the first full backup is created, the earliest incremental backup is merged with the earliest full backup.If you specify two full backups in your plan settings, the last two chains will be stored, if you specify three full backups, the last three chains will be stored, and so on.
All backups are retained if you delete a disk, cloud server, or backup plan.
Backups can be deleted manually.
Cost
Backup storage is paid for using the cloud platform payment model.
The cost of backup storage depends on the size of the backup and the pool segment in which it is stored. Only backups with AVAILABLE or RESTORING statuses are paid for, backups with other statuses are not paid for.
Each GB of backup storage is paid for. If the backup size is less than 1 GB, the paid amount is rounded up to 1 GB.
For example, you store a 512 MB backup in the ru-9a pool segment. The cost of storing the backup will be equal to the cost of storing 1 GB in this pool segment — 3.66 ₽ per month.
The cost per GB of backup storage can be viewed at selectel.ru.
To see the actual backup size, you can view the actual backup size in the control panel in the top menu, click Products and select Cloud Servers → Backups → Backups tab . To see the total amount of backups that are paid for, you can go to Cloud Platform → Platform Consumption → Current Cost tab.