Understanding Private Cloud Storage
Posted by
Howard Marks
November 30, 2009
This architecture provides two major benefits. First, storage administrators can configure and provision new storage nodes quickly and inexpensively. Second, administrators can add capacity only as demand requires, instead of purchasing additional disk space to meet anticipated future growth and then having that capacity sit idle in the present.
However, there are also trade-offs. Cloud storage is best suited to unstructured data, such as medical images, engineering drawings, and Office documents. For another, because each x86 server isn't as reliable as a high-end enterprise disk array, a private cloud must store copies of the data on multiple nodes. This requires more raw disk space than an enterprise disk array using a RAID-5 or 6 system. For example, if you set a policy for your private cloud to keep three copies of a 60-GB file for data protection, it would require 180 GB of disk, whereas a 6+2 RAID-6 system would need just 80 GB.
Beyond Low Cost
Several other vendors include location-aware policy engines that copy data to nodes in specific geographical locations. Data Direct Networks' Web Object Store, Bycast's StorageGrid, and EMC's Atmos systems can specify that two copies of each object in a folder should be stored in New York and Los Angeles, and that copies also should be stored in two other locations.
This not only protects data from data center failures but can also put objects on storage clusters close to the users who need them. Bycast's policy engine takes this notion one step further by including elements, such as storage tiering, that can migrate objects from more-expensive to less-expensive disk, and even to and from tape.
Organizations planning to offer private cloud storage services to internal departments may want to consider multitenant features that allow storage to be partitioned among different groups. For example, IT could carve out one section of the private cloud for HR and another for marketing, and then charge those departments based on usage. This means having delegated administration models and/or virtual servers that restrict each group's access and visibility to only their own data and the resources assigned to them. A multitenant storage system should also include accounting features that collect usage data, such as peak utilization, that will help IT in determining chargebacks.
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