Which of the following is a common characteristic of ephemeral storage?

Ephemeral storage is characterized primarily by its temporary nature; it exists only during the runtime of an instance or application. This type of storage is typically used in cloud environments where resources can be started and stopped dynamically. When an instance that utilizes ephemeral storage is terminated, all data stored in that ephemeral storage is lost.

This characteristic is particularly useful for transient workloads, such as processing data for a short time or caching outputs where long-term data persistence is not necessary. The focus on efficiency and speed—relying on fast access and lower costs—aligns well with the nature of ephemeral storage, which is designed to be temporary.

In contrast, the other options do not accurately reflect the nature of ephemeral storage. It is not always available, as it depends on the state of the instance. It also doesn't retain data after a shutdown; once the runtime environment ceases, the data is non-recoverable. Lastly, ephemeral storage does not inherently include backup capabilities, since its design does not support data longevity.