System and data disks for cloud servers

Different flavors of cloud servers are allocated different sizes and numbers of system and data disks.

To see what disk configuration is associated with each flavor, use the Cloud Control Panel to display the options available to you when you create a server.

For example, compare the disk configuration offered for a server with 60 GB of RAM in two different flavor classes:

  • In the I/O flavor class, the configuration for this server includes a 40-GB system disk and 600-GB data disk (addressable as two disks).

  • In the Compute flavor class, the configuration for this server includes a 50-GB system disk and no data disk.

System disk

The system disk, also called the boot disk, is the first disk from which the server will attempt to access and boot, much like the first physical hard drive plugged into a physical computer. Operating systems are installed on this disk by default. Data can be stored on a system disk, although it might have less capacity than any attached data disks.


To make a backup copy of a system disk, use Cloud Images to create a bootable backup.

Data disks

Data disk space is in addition to the system disk. Some Cloud Servers flavors do not have data disks assigned to them. If your server has a data disk, it is available to use for your application data, caching, or other purposes.

Data disks are provided as empty or raw disks in some cases, to provide you maximum flexibility in how you use them. Before you can use a data disk, you might need to format it, partition it, or group it into a software RAID group.

To prepare a data disk for use on a cloud server, follow the steps appropriate for that server’s operating system:


To make a backup copy of a data disk, use one of the following services:

  • Cloud Backup for incremental backups, such as for disaster recovery

  • Cloud Block Storage for portable backups, such as for relocation to new servers