Frequently Asked Questions: Cloud Storage
By SNIA Cloud Storage Initiative

What is Cloud Storage?

Cloud storage is not a new technology in itself – it is a new business model wrapped around technologies, such as virtualization, to reduce the cost of using information technology resources. Cloud storage takes advantage of Web-based technologies to allow scalable, virtualized IT resources to be provided as a service over the network.

What is Cloud Storage used for?

Cloud storage can be implemented in many different ways. For example: local data (such as on a laptop) can be backed up to cloud storage; a virtual disk can be “synched” to the cloud and distributed to other computers; and the cloud can be used as an archive to retain (under policy) data for regulatory or other purposes.

How does SNIA define Cloud Storage?

SNIA defines Cloud Storage as Data Storage as a Service (DaaS) encompassing all these approachs. DaaS is defined as the delivery of virtualized storage on demand over a network appropriately configured (with virtual storage and related data services), based on a request for a given service level. By abstracting data storage behind a set of service interfaces and delivering it on demand, a wide range of actual offerings and implementations are possible.

How is SNIA addressing the Need for Standardization?

This need is addressed by the SNIA in its new Cloud Data Management Interface (CDMI). Designed to enable interoperable cloud storage and data management, the CDMI specification is aggressively addressing a total cloud storage solution – helping users avoid the chaos of proprietary advances and partial solution APIs that would erode the integrity of the cloud model.

Easy to implement, CDMI integrates and is interoperable with various types of client applications and is compatible with current public cloud storage offerings like Amazon, Iron Mountain, Nirvanix, etc. CDMI offers standard approaches to data portability, compliance and security, as well as the ability to connect one cloud provider to another, enabling compatibility among cloud vendors.

How does CDMI work?

Providing both a data path for the cloud and a management path for the cloud data, CDMI is the functional interface that applications will use to Create, Retrieve, Update and Delete (CRUD semantics) data elements in the cloud. As part of this interface, the client will be able to discover the capabilities of the cloud storage offering and use this interface to manage containers and the data that is placed in them.

What about Other Legacy Interfaces?

CDMI provides not only a data object interface, it also can be used to manage containers exported for use by cloud computing infrastructures. The notion of a container is used in CDMI as an abstraction of the underlying storage space in a cloud. This is not only a useful abstraction to represent storage space, but a container also serves to represent a grouping of the data stored in it, and a point of control for applying data services in the aggregate. This is accomplished in CDMI through an “export” function that enable various protocols to access a CDMI container. The access controls for these protocols are part of the CDMI interface to ensure secure, protected access. Typically the container is thin provisioned at an “advertized” size the applications see through these protocols (i.e. LUN size). This size can be arbitrarily large in order to not run out of space during normal operations. CDMI accounting shows the actual usage within this size that is part of the actual bill.

How does CDMI address Data Security?

Authorization and authentication in the data path of CDMI is done using the same mechanism as in NFS, a secure standard in wide use where the threat models are well known. CDMI also allows control over the access control of legacy interface used when containers are exported via those protocols. CDMI also has Data System Metadata that allows the data to be encrypted when stored on the underlying infrastructure – an important capapbility in multi-tenant situations such as public clouds. Lastly CDMI provides for a secure delete mechanism (with various algorithyms) for data that has expired

What other Metadata does CDMI Standardize?

CDMI uses many different types of metadata, including HTTP metadata, data system metadata, user metadata, and storage system metadata. To address the requirements of enterprise applications and the data managed by them, this use of metadata allows CDMI to deliver simplicity through a standard interface.

How does the Metadata Approch work?

CDMI’s use of metadata extends from individual data elements and can apply to containers of data, as well. Thus, any data placed into a container essentially inherits the data system metadata of the container into which it was placed. When creating a new container within an existing container, the new container would similarly inherit the metadata settings of its parent container. Of course, the data system metadata can be overridden at the container or individual data element level, as desired.

The extension of metadata to managing containers, not just data, enables a reduction in the number of paradigms for managing the components of storage – a significant cost savings. By supporting metadata in a cloud storage interface standard and proscribing how the storage and data system metadata is interpreted to meet the requirements of the data, the simplicity required by the cloud storage paradigm is maintained, while still addressing the requirements of enterprise applications and their data.

What will initial CDMI Implementations look like?

Since CDMI can be used as both a Data Path and a Management Path, there are several ways to roll out an implementation of CDMI for a public cloud. First of all, CDMI can be deployed side by side with existing proprietary interfaces. This allows existing applications to move over to the standard interface as they desire to take advantage of the features. The side-by-side deployment allows the dame data to be accessed via either interface and no movement of data is required. As the cloud provider adds additional data services and capabilities to their service, the CDMI interface can be used by the application to ensure that the existing data’s requirements are being met using those new services. If the cloud provider implements the CDMI accounting, that can be used by the customer to administer the security and programmatically access their bill.

CDMI has many capabilities and not all will be implemented by every cloud offering. CDMI has capability resources that let a client application programticaly find out which capabilities are actually implemented before tryng to use them. This also allows new cloud offerings to use CDMI as the initial interface for their service, expanding the implementation of CDMI as their offering increases in capabilities. CDMI is also extensible to accommodate services and features that are not yet standardized, obviating the need for a separate proprietary interfaces for those functions.

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