Network disk backups
You can create backups network disks cloud servers in two ways:
- configure automatic scheduled backups. Create a backup plan, specify backup schedule and add network disks to the plan — more details in subsection Configure scheduled backups. Scheduled creation can be configured complete 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 — more details in subsection Create backup manually. You can only create manually complete backup.
The service is based on OpenStack Karbor and Cinder components.
To see alternative ways of backing up cloud servers, see the following table Backup methods.
Full backup
A full backup is a complete backup of a disk with all data.
Full backups can be created automatically by 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 according to the plan. 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 be created only automatically by schedule.
Incremental backups are created daily at the time specified in the backup plan settings. A full backup is created first, then it is created once a week. Incremental backups are created on all other days.
Creating backups
We guarantee consistency of copies at the level of crash-consistency. At the moment of creation, the data that is on the disk is written to the backup. Also in the backup can be written "dirty data", which appear when overwriting or deleting files on disk. 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.
Storage of backups
Full and incremental backups are stored in the Ceph repository — in each pool segment a cluster is deployed. 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.
You can't download the backup, but you can use it. disk recovery — a new disk of the same type and size as the original disk 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 not limited. At the same time, there is a limit on creation within one plan: for plans with full backups — 90 backups, for plans with incremental backups — 14 full backups and 78 incremental backups.
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 incremental backup chains 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 specified two full backups in the plan settings, the last two chains will be stored, if you specified 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 manual deletion.
Cost
Storage of backups is charged at cloud platform payment models.
The cost of backup storage depends on the size of the backup and pool segment where it is stored. Backup storage is paid for only from statuses AVAILABLE or RESTORINGBackups in 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 size of the backup, go to control panels from the top menu, press Products and select Cloud servers → Backups → tab Backups. To see the total amount of backups that are paid for, see Cloud platform → Platform consumption → tab Present value.