14-07-2012, 10:06 AM
Cloud storage
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Cloud storage is a model of networked online storage where data is stored on virtualized pools of storage which are generally hosted by third parties. Hosting companies operate large data centers; and people who require their data to be hosted buy or lease storage capacity from them and use it for their storage needs. The data center operators, in the background,virtualize the resources according to the requirements of the customer and expose them as storage pools, which the customers can themselves use to store files or data objects. Physically, the resource may span across multiple servers.
Cloud storage services may be accessed through a web service application programming interface (API), or through a Web-based user interface.
[edit]Cloud storage architecture
Cloud storage has the same characteristics as cloud computing in terms of agility, scalability, elasticity and multi-tenancy. According to Mary-Ann Baldwin[1], it was invented by NC State University in 2003. [2] [3] [4] Although the foundation may be comprised of block storage or file storage, cloud storage is typically exposed to consumers as files or objects. In practice, as demonstrated by Amazon S3, objects have proven to be a highly scalable, available and reliable layer of abstraction that also minimizes some of the common limitations of file systems, such as maximum file system size. For example, a single ext3 file system is limited to 32TB. Scaling to typical capacity requirements would require multiple file systems. Managing multiple file systems independently, while accounting for optimal utilization, provisioning, de-provisioning, clean-up and other optimizations would require significant overhead.
It is difficult to pin down a canonical definition of cloud storage architecture, but object storage is reasonably analogous. Cloud storage services like Amazon S3, cloud storage products like EMC Atmos, and distributed storage research projects like OceanStore[5] are all examples of object storage and infer the following guidelines.
Cloud storage is:[5]
comprised of many distributed resources, but still acts as one
highly fault tolerant through redundancy and distribution of data
highly durable through the creation of versioned copies
typically eventually consistent in regards to data replicas
[edit]Cloud storage advantages
Companies need only pay for the storage they actually use.[6]
Private Cloud Computing
Public Cloud Computing
Companies do not need to install physical storage devices in their own datacenter or offices, which reduces IT and hosting costs.[6]
Storage maintenance tasks, such as backup, data replication, and purchasing additional storage devices are offloaded to the responsibility of a service provider, allowing organizations to focus on their core business [6]