Clotho: Transparent Data Versioning at the Block I/O Level Michail D. Flouris Angelos Bilas1 Department of Computer Science, Institute of Computer Science University of Toronto, Foundation for Research and Technology - Hellas 10 King’s College Road, Vassilika Vouton, P.O.Box 1385, Toronto, Ontario M5S 3G4, Canada GR 711 10 Heraklion, Greece Tel: +1-416-978-6610, Fax: +1-416-978-1931 Tel: +30-281-039-1600, Fax: +30-281-039-1601 e-mail: fl
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[email protected] Abstract cessing, and network transfer capacity in a cost-efficient manner and they will be able to process and store ever in- Recently storage management has emerged as one of the main creasing amounts of data. The cost of managing these large problems in building cost effective storage infrastructures. One amounts of stored data becomes the dominant complex- of the issues that contribute to management complexity of stor- ity and cost factor for building, using, and operating mod- age systems is maintaining previous versions of data. Up till now ern storage systems. Recent studies [10] show that stor- such functionality has been implemented by high-level applica- age expenditures represent more than 50% of the typical tions or at the filesystem level. However, many modern systems server purchase price for applications such as OLTP (On- aim at higher scalability and do not employ such management entities as filesystems. Line Transaction Processing) or ERP (Enterprise Resource Planning) and these percentages will keep growing. Fur- In this paper we propose pushing the versioning functionality thermore, the cost of storage administration is estimated at closer to the disk by taking advantage of modern, block-level several times the purchase price of the storage hardware storage devices.