Prof. Eitan Bachmat

Continuous Data Protection or CDP is a method for capturing all changes occurring to a storage device, allowing fine granularity restore of objects from crash consistent images. In this paper we introduce a method for creating a virtual image of a block storage device,using a CDP journal log and an image of the device at one point in time. The creation of the disk image for any point in time is created on demand. The creation algorithm is very efficient and takes only a few minutes for multiple TeraBytes of changes. The algorithm for creating the image can be formalized as a map/reduce algorithm and can be parallelized easily over multiple machines to reduce the creation time. The creation on demand of the virtual image using journaling methods, minimizes the effect on the production volumes, allowing the use of CDPs for enterprise class applications.