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|Revivio CPS appliance logical architecture|
The Revivio Continuous Protection System (CPS), a SAN-based appliance, creates an additional set of mirrored volumes that can be restored back to any point in time.
CDP products target different company needs. Some products are software-based, while others are appliances; solutions may operate at the application, file system or volume level; some are agentless, while others require host-based agents and/or drivers. The degree of recovery granularity can vary significantly among the products as well (see "CDP products"). Here are some examples of companies with CDP products:
Revivio Inc. The Revivio Continuous Protection System (CPS) is a storage area network (SAN)-based appliance designed to operate in parallel with an application's primary data storage. Designed to meet enterprise-class data requirements, it incorporates high levels of fault-tolerance, including redundant, hot-swappable components and fault tolerant cache. It also doesn't require software applications, agents or drivers to be installed on host servers. Instead, the Revivio appliance presents storage LUNs to host servers and leverages the (presumably) already existing host-based volume management software--such as Veritas Volume Manager--to operate as an additional set of mirrored volumes for an application (see "Revivio CPS appliance logical architecture").
Optimized to support a high I/O transaction rate, the Revivio CPS appears to the host as an additional write-only mirrored volume. However, as data is subsequently written to the CPS, the data that is replaced is maintained in a time-stamped log. The appliance then provides the ability to present to any host a virtual view, or TimeImage, of any set of protected volumes exactly as they appeared at a specific point in time. The disk storage that actually holds this data can be any SAN-based storage available in the environment. Depending on desired data protection policies, it can range from mirrored EMC Symmetrix volumes to low-cost JBOD.
In the event of data loss or corruption, recovery consists of "dialing back" in time to identify the point in time immediately prior to the loss, verifying the validity of the data and presenting this TimeImage volume back to the host.
The result is a solution that provides a level of protection similar to split mirror technology, but typically requires less storage while providing far more granularity and faster recovery times. Revivio is best suited for enterprise-class applications running on databases that have significant RPO and RTO restrictions.
FilesX Inc. FilesX Xpress Restore and Xchange Restore are two software products that address a different portion of the market. Technically, these could be considered next-generation snapshot products, rather than continuous backup, but they share many CDP-type characteristics.
Built upon snapshot technology, FilesX doesn't capture every change that takes place, but instead performs regularly scheduled snapshots sending changed data to a central repository. The granularity of these snapshots can range from a few minutes to hours, according to Jacob Herbst, CEO of FilesX, with the sweet spot being one to two hours. While FilesX is not a true continuous backup solution when compared to the other products, it offers a significantly improved level of granularity for Microsoft Exchange and Windows file server environments than is achieved by traditional backup means.
The real value is to be found in the product's recovery capability. FilesX captures block-level changes, transfers them to a repository and then can map those changes to a file-level view. This provides multiple generations of virtual images similar to a CDP application. Imagine being able to open an Explorer-like window showing one or more generations of Exchange Information Stores, and being able to quickly navigate through mailboxes and messages, select those to be recovered and drag and drop them to the current active information store. Or imagine an e-mail virus attack, where you are able to view the history of snapshots, locate the most recent prior to the attack and then right-click and restore the information store.
This was first published in June 2004