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Difference between the disk value and the ephemeral value

Question & Answer


Question

What is the difference between the disk value and the ephemeral value as it is defined by openstack and pertains to IBM SmartCloud Orchestrator?

Answer

The following descriptions explain the difference:

  • Disk:
    The value of virtual root disk size is in gigabytes. It is an ephemeral disk into which the base image is copied. When you boot from a persistent volume, it is not used. The "0" size is a special case that uses the native base image size as the size of the ephemeral root volume.
  • Ephemeral:
    The value specifies the size of a secondary ephemeral data disk. It is an empty, unformatted disk and it exists only for the life of the instance.

The disk must be specified as it is the primary disk and the image is copied to that disk. The ephemeral value is a secondary disk that is optional and used as additional disk space. For example, it might be used if the user wants to separate image data and business data. It might also be used if the user temporarily needs more disk space without losing the image data on the primary disk.

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Document Information

Modified date:
17 June 2018

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swg21646032