Definition
A point-in-time copy is a copy of original data as it appeared at a point in time. In a conventional backup operation, users often create a PiT Copy, while an application is in quiescing, to make the PiT Copy a consistent copy of original data.
Key Points
There are two popular implementation techniques for creating PiT Copies inside a storage system: split mirror and copy on write.
Split mirror is a technique for replicating the original data at a point in time. In some implementations, a storage system replicates the original data, and when users create the PiT Copy, a storage system splits the replication. Copy on Write (CoW) is a technique for capturing data changes to storage and creating a PiT Copy after specifying the point in time. In some implementations, when users create the PiT Copy, a storage system creates its image with both the original data and the modified data.
Techniques for creating PiT Copies have a trade-off between occupied...
Recommended Reading
Alain Azagury, et al. Point-in-time copy: yesterday, today, and tomorrow. In: Proceedings of IEEE symposium confernce on mass storage systems and technologies. 2002.
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Fujimoto, K. (2016). Point-In-Time Copy. In: Liu, L., Özsu, M. (eds) Encyclopedia of Database Systems. Springer, New York, NY. https://doi.org/10.1007/978-1-4899-7993-3_1339-2
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DOI: https://doi.org/10.1007/978-1-4899-7993-3_1339-2
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