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キーワード:
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要旨:
Many wide-area storage systems replicate data for durability. A common way of
maintaining the replicas is to detect node failures
and respond by creating additional copies of objects that were stored on failed
nodes and hence suffered a loss of redundancy. Reactive techniques can minimize
total bytes sent since they only create replicas as needed; however, they can
create spikes in network use after a failure. These spikes may overwhelm
application traffic and can make it difficult to provision bandwidth.
This paper explores a proactive approach that creates additional copies not in
response to failures, but periodically at a fixed low rate. We introduce Tempo,
a distributed hash table that allows each user to specify a maximum maintenance
bandwidth and uses it to perform proactive replication. Results from a
simulation study suggest that Tempo can deliver high durability despite only
using several kilobytes per second of bandwidth, comparable to state-of-the-
art reactive systems.
