# Constraints

#### General

- A vault can be associated with only one backup policy.
- A vault can be associated with a maximum of 256 resources.
- A maximum of 32 backup policies can be created.
- Only the backups in a vault whose status is Available or Locked can be used for data restoration.
- Backups in a vault whose status is Deleting cannot be deleted.
- When Storage Disaster Recovery Service (SDRS) is used to set up disaster recovery for cloud servers, restorations can be performed at the disaster recovery site only after protection is disabled.
- Backups cannot be downloaded to a local PC or uploaded to OBS.
- A vault and its associated servers or disks must be in the same region.

#### Cloud Disk Backup

- Only disks in the Available or In-use state can be backed up.
- A new disk must be at least as large as the backup's source disk.

#### Cloud Server Backup

- Shared disks on a server can be backed up, but there can be no more than 10 shared disks.
- Only backups in a vault whose status is Available or Locked can be used to create images.

- You can choose to back up only specified disks on a server but such a backup of disks must be restored as a whole. File- or directory-level restoration is not supported.
- When SDRS is used to set up disaster recovery for cloud servers, restorations can be performed at the disaster recovery site only after protection is disabled.
- You are advised not to back up a server whose disk size exceeds 4 TB.

Parent topic: Service Overview