There are two fluffy clouds overlapping one another. One is smaller and sits against the larger one in a single image. It is found on the Windows SkyDrive application.
This OneDrive icon is made in Material Design style
developed by Google. This style is based on extremely simplified shapes, thin two-pixel lines, and is optimized for 24x24 px. Unlike other vector icon packs that have merely hundreds of icons, this icon pack contains 6,200 icons, all in the same style and quality.