General information about cloud server network volume backups
You can create backups of network volumes for cloud servers in two ways:
- configure automatic scheduled backups. Create a backup plan, specify a backup schedule, and add network volumes to the plan — for more details, see the subsection Configure scheduled backups. You can configure scheduled creation of full or incremental backups;
- manually — to freeze the system state and store the backup remotely from the volume. You do not need to configure a plan to create a manual backup — for more details, see the subsection Create backup manually. You can only create a full backup manually.
The service is powered by OpenStack Karbor and Cinder components.
Records of network volume backup operations are saved in audit logs.
You can view alternative ways of creating cloud server backups in the Backup methods table.
Full backup
A full backup is a complete reserve copy of a volume with all data.
Full backups can be created automatically on a schedule or manually.
You can configure a schedule for creating full backups by day of the week or via a 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 state of the volume and the previous planned backup. This backup is created faster than a full backup and takes up less space because it stores only the changes on the volume.
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 performed once a week. On the remaining days, incremental backups are created.
Creating backups
We guarantee copy consistency at the crash-consistency level. At the time of creation, the data present on the volume is recorded into the backup. "Dirty data" that appears when files are overwritten or deleted on the volume may also be recorded in the backup. Data in the cloud server memory is not recorded into the backup. Due to "dirty data," the size of a full backup may exceed the actual volume of data and files on the volume; an incremental backup may exceed the difference between the current data volume and the size of the previous backup.
Creating a backup does not affect cloud server performance—all operations take place on Selectel's computing resources. When creating a full backup, an instant snapshot of the volume is created; there is no increase in load on the cloud server. When creating an incremental backup, changes between the current state of the volume and the previous backup are calculated on the fly, and the difference between states is transferred to the backup storage.
Backup storage
Full and incremental backups are stored in three copies on a dedicated group of hardware:
- in single-availability zone pools in each pool segment an isolated storage cluster is deployed. It stores backups and volumes—this increases the speed of creating backups and restoring from them;
- in the multi-availability zone pool ru-6, a shared storage cluster is used for all pool segments. This allows you to restore a volume from a backup in any pool segment and with any volume type.
This storage method ensures data integrity even if the servers on which the volumes are located fail.
A backup cannot be downloaded, but you can restore the volume from it — a new volume of the same type and size as the original will be created.
Backups created automatically on a schedule are stored in chains of seven: one full and six subsequent incremental ones. The plan specifies how many full backups to keep (at least two). For example, if the plan settings specify storage for three full backups, the three most recent backup chains will be kept.
Backup storage limitations
If backups are created automatically according to a schedule, the total number of backups in one project is unlimited. However, there are limits on creation within a single plan: 90 backups for plans with full backups, and 14 full and 78 incremental backups for plans with incremental ones.
You can store no more than 1 000 manually created backups in a single project.
Automatic backup deletion
Only for backups created automatically on a schedule.
In the plan settings, when choosing to store the latest backups, you specify how many of the latest full backups or incremental backup chains to keep. When a new full backup is created for a volume, the service checks the total number of full backups for the volume under 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 and six subsequent incremental ones. A week after the first full backup is created, the earliest incremental backup is merged with the earliest full backup. If you specified in the plan settings to keep two full backups, the two latest chains will be kept; if three full backups, the three latest chains, and so on.
All backups will be saved if you delete the volume, cloud server, or backup plan.
Backups can be deleted manually.
Cost
Backup storage is paid based on the cloud platform's payment model.
The cost of backup storage depends on the backup size and the pool segment where it is stored. Only backup storage with statuses AVAILABLE or RESTORING is charged; backups in other statuses are not charged.
Every GB of backup storage is charged. If a backup size is less than 1 GB, the billable volume is rounded up to 1 GB.
For example, you store a 512 MB backup in the pool segment ru-9a. The storage cost for the backup will be equal to the cost of storing 1 GB in this pool segment—4.02 ₽ per month.
The cost of one GB of backup storage can be viewed at selectel.ru.
You can view the actual size of a backup in the Control panel: in the top menu, click Products and select Cloud servers → section Backups → tab Backups. You can also view the total billable volume of backups in the Control panel: in the top menu, click Products → Cloud servers → section Platform consumption → tab Current cost.