FAST '08 – Abstract
Pp. 1–16 of the Proceedings
Pergamum: Replacing Tape with Energy Efficient, Reliable, Disk-Based
Archival Storage
Mark W. Storer, Kevin M. Greenan, and Ethan L. Miller, University of California, Santa Cruz;
Kaladhar Voruganti, Network Appliance
Abstract
As the world moves to digital storage for archival purposes, there
is an increasing demand for reliable, low-power, cost-effective,
easy-to-maintain storage that can still provide adequate performance
for information retrieval and auditing purposes. Unfortunately, no
current archival system adequately fulfills all of these
requirements. Tape-based archival systems suffer from poor random
access performance, which prevents the use of inter-media redundancy
techniques and auditing, and requires the preservation of legacy
hardware. Many disk-based systems are ill-suited for long-term
storage because their high energy demands and management
requirements make them cost-ineffective for archival purposes. Our solution, Pergamum, is a distributed network of
intelligent, disk-based, storage appliances that stores data
reliably and energy-efficiently. While existing MAID systems keep
disks idle to save energy, Pergamum adds NVRAM at each node to
store data signatures, metadata, and other small items, allowing
deferred writes, metadata requests and inter-disk data verification
to be performed while the disk is powered off. Pergamum uses
both intra-disk and inter-disk redundancy to guard against data
loss, relying on hash tree-like structures of algebraic signatures
to efficiently verify the correctness of stored data. If failures
occur, Pergamum uses staggered rebuild to reduce peak energy
usage while rebuilding large redundancy stripes. We show that our
approach is comparable in both startup and ongoing costs to other
archival technologies and provides very high reliability. An
evaluation of our implementation of Pergamum shows that it
provides adequate performance.
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