4/18/2002
3:30pm-4:30pm
ECCR 265
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Improving the Performance of Storage Servers
Department of Computer Science, Princeton University
Current technology trends indicate a widening gap between processor speed and
disk access time. As a result, storage I/O has become a very serious bottleneck
for many I/O-intensive applications such as databases. In this talk, I will
present two solutions to improve the storage server performance: effective
storage server caching; and minimizing I/O-related host overheads.
Effective caching is an important method to reduce the latency and improve the
throughput of I/O operations of a storage server. Although the file caching and
database caching have been studied extensively during the past decades, it is
not well understood how to effectively manage the cache memory of a storage
server in a multi-tier storage infrastructure where there are three levels of
caches: client cache, file or database cache and storage server cache. Our
research studied the access patterns to storage server caches with several
commercial workloads. Based on our analysis of access patterns, we derived a
multi-queue algorithm for storage server caching. Our experimental results with
simulation and implementation show that this algorithm is quite effective. For
several OLTP database workloads, this method can achieve the same hit ratios as
the commonly-used LRU algorithm with a twice large storage cache.
Minimizing I/O-related host overheads is a key to improve the performance of a
network attached storage server. Recent studies have shown that storage I/Os
have very high overheads on database servers, especially for OLTP workloads. To
alleviate these overheads, we have studied the effects and design issues of
using user-level communication to connect a database system with a storage
server. Our results with OLTP workloads show that substantial enhancements are
required to effectively use user level communication as a storage area network.
We have developed a direct storage access API to fully exploit the benefits of
user level communication. This method can reduce the I/O related overheads by
40% and improve the database transaction rate by 18% for OLTP workloads.
Hosted by Dirk Grunwald.
Refreshments will be served immediately following the talk in ECOT 831.
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