DATE: Thursday, January 25 , 2007
TIME: 12:00 pm - 1:00 pm
PLACE: Wean Hall 8220

Liuba Shrira
Brandeis University - CSD

Split Snapshots: A New Approach to Old State Storage

Kurzweil says, computers will enable people to live forever and doctors will be doing backup of your memories by late 2030. This talk is not about that, yet. Instead, the remarkable drop in disk costs makes it possible and attractive to retain past application states and store them for a long time for mining or auditing. A still open question is how to best organize the past state storage? Split snapshots are a recent approach to past state storage that is attractive for several reasons. Split snapshots are persistent, can be taken with high-frequency, and they are transactionally consistent. Unmodified database code can run against them. Like no other past state storage approach, they provide low-cost discriminated garbage collection of snapshots, a useful feature in long-lived systems.

A number of novel techniques underly split snapshots. A new in-memory data-structure creates consistent copy-on-write snapshots without blocking, a new persistent data structure provides high performance versioned meta-data, and a new snapshot storage organization allows to gradually garbage collect selected copy-on-write snapshots without copying and without creating disk-fragmentation. Measurements of a split snapshot prototype system indicate that the new techniques are efficient and scalable, imposing minimal 4% performance penalty on a storage system, on expected common workloads. (Joint work with Ross Shaull and Hao Xu)


Liuba Shrira is an associate Professor in the Computer Science Department at Brandeis University, and is affiliated with the Computer Science and Artificial Intelligence Laboratory at MIT. She received her PhD from Technion (Israel) what feels like yesterday, working with Nissim Francez, Michael Rodeh and Oded Goldreich on theoretical aspects of distributed algorithms. From 1986 to 1997 she was a researcher in the MIT Programming Methodology Group with Barbara Liskov. She joined Brandeis in 1997. In 2004-2005 she was a visiting researcher at Microsoft Research, Cambridge, UK.

Her research interests span aspects of design and implementation of distributed systems and especially storage systems. This includes fault-tolerance, availability and performance issues. Her recent focus is on long-lived transactional storage, time travel (in storage), software upgrades, byzantine faults, and support for collaborative access to long-lived objects.

Visitor Host:
Garth Gibson

Visitor Coordinator:
Angela Miller, 8-6645,

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