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                   B O S T O N   U N I V E R S I T Y
                                       
                      Computer Science Department
                                       
                          C O L L O Q U I U M
                                       
            Architecting for earthquakes: fault tolerant storage

			   Elizabeth Borowski

			 Storage Systems Program

		          Hewlett Packard Labs


			 Wednesday, March 10th 
                                       
                                11:00am
                       (Coffee served at 10:45am)

                                       
                         Seminar Room / MCS 135
                                       

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In today's information-centric global marketplace, business critical
data must be available all the time. Rain or shine, earthquake in
California or tornado in Kansas, the data center needs to be on-line
meeting quality of service guarantees twenty-four hours a day, seven
days a week, with no exceptions. This dire need for continual high
performance and high availability is best met by an active system that
can monitor, diagnose, and repair itself on the fly.  Key design
features are on-line load balancing, fluid scalability, and automatic
recovery from failure.

In the Palladio project at HP Labs we are designing a fault tolerant
distributed storage system to meet these goals.  The advent of high
speed back-end storage networks enables distributed storage to
be accessed as quickly as a local disk. These SANs (storage attached
networks) facilitate access to large pools of heterogeneous storage by
multiple hosts.  In order to achieve automatic load balancing and
fault tolerance, our approach is to hide the details of the underlying
data placement from the hosts.  The upper layers of the system see
only a virtual store abstraction of the data.  Maintaining this
abstraction, while still providing quality of service guarantees and
data coherency, is not trivial. This is especially true in the face of
network partitions, device crashes, and failures in the storage
management system.  In this talk I will discuss the architectural
choices we've made in designing the storage management system, and
present in detail our solution to disaster recovery. I will prove the
liveness and safety properties of the recovery protocol. Namely, I
will show the system eventually recovers from the failure (if at all
possible) and that data coherency is guaranteed throughout. 


Host: Azer Bestavros (best@cs.bu.edu)

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For colloquium info, including directions, see http://cs-www.bu.edu/colloquium
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