Cloud the bottom of the hierarchy. Clouds in the troposphere assume five physical forms based on structure and process of formation. These forms are commonly used for the purpose of satellite analysis. They are given below in approximate ascending order of instability or convective activity. "Non-convective" stratiform clouds appear in "stable" airmass conditions and, in general, have flat sheet-like structures that can form at any altitude in the troposphere. The stratiform group is divided by altitude range into the genera cirrostratus (high-level), altostratus (mid-level), stratus (low-level), and nimbostratus (multi-level). Fog is commonly considered a surface-based cloud layer. The fog may form
Rackspace Cloud supported standard such as WebDAV. There are no concepts of "appending" or "locking" data within Cloud Files (which may affect some disk mirroring or backup solutions), nor support for permissions or transcoding. Data is organised into "containers" but it is not possible to create nested folders without a translation layer. Cloud Servers is a cloud infrastructure service that allows users to deploy "one to hundreds of cloud servers instantly" and create "advanced, high availability architectures" similar to the Amazon Elastic Compute Cloud. The "cloud servers" are virtual machines running on the Xen hypervisor for Linux-based instances, and Citrix XenServer for