General information about cloud server network volume backups
You can create backups of network volumes of cloud servers in two ways:
- configure automatic scheduled backups. Create a backup plan, specify a backup schedule, and add network volumes to the plan — see Configuring scheduled backups. You can configure scheduled full or incremental backups;
- manually — record the system state and store the backup remotely from the volume. You do not need to configure a plan to create a manual backup — see Create backup manually. Only a full backup can be created manually.
The service is powered by OpenStack Karbor and Cinder components.
Records of network volume backup operations are saved in audit logs.
Alternative ways to create cloud server backups can be found in the Backup methods table.
Full backup
A full backup is a complete backup of a volume 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 volume state and the previous backup created as planned. 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 created once a week. Incremental backups are created on the remaining days.
Creating backups
We ensure crash-consistency of copies. At the time of creation, the data present on the volume is written to the backup. "Dirty data" that appears when files are overwritten or deleted on the volume may also be written to the backup. Data in the cloud server memory is not written to the backup. Due to "dirty data," the size of a full backup may exceed the actual volume of data and files on the disk; an incremental one 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 are performed on Selectel's computing resources. When a full backup is created, an instant disk snapshot is taken, and no load increase occurs on the cloud server. When creating an incremental backup, the changes between the current volume state 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 equipment cluster:
- in single-AZ pools, an isolated data storage cluster is deployed in each pool segment. Backups and volumes are stored there — this increases the speed of creating backups and restoring from them;
- in multi-AZ pools ru-6, a data storage cluster common to all pool segments is used. This allows restoring a volume from a backup in any pool segment and with any disk type.
This type of storage ensures data safety even in case of failures on the servers where the volumes are located.
Backups cannot be downloaded, but you can restore the volume — a new volume of the same type and size as the original one 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 (minimum — two). For example, if the plan settings specify keeping three full backups, the three most recent backup chains will be kept.
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 limitation on creation within a single plan: for plans with full backups — 90 backups; for plans with incremental ones — 14 full backups and 78 incremental ones.
A maximum of 1,000 manually created backups can be stored per project.
Automatic backup deletion
Only for backups created automatically on a schedule.
In the plan settings, when selecting the retention of the latest backups, you specify how many 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 the volume's full backups within a single 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 — one full and six subsequent incremental ones. One week after the first full backup is created, the earliest incremental backup is merged with the earliest full backup. If you specified keeping two full backups in the plan settings, 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 for according to the cloud platform payment model.
The cost of backup storage depends on the backup size and the pool segment where it is stored. Only backups with statuses AVAILABLE or RESTORING are charged; backups in other statuses are not charged.
Each GB of backup storage is charged. If the backup size is less than 1 GB, the volume is rounded up to 1 GB.
For example, you store a 512 MB backup in the ru-9a pool segment. The storage cost for the backup will equal the cost of storing 1 GB in this pool segment — 4.02 ₽ per month.
The cost per 1 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 volume of chargeable backups in the Control panel: in the top menu, click Products → Cloud servers → section Platform consumption → tab Current cost.