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University of Colorado at Boulder
Department of Computer Science
ECOT 717 Engineering Center
Campus Box 430
Boulder, Colorado 803090430
(303) 4927514, FAX: (303) 4922844

CS COLLOQUIUM
Improving the performance of storage servers
Yuanyuan Zhou
Princeton University
DATE
3:30  4:30 PM
Engineering Center Classroom 265

Refreshments will be served afterwards in ECOT 832

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. Forseveral 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 connecta 
databasesystem 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.
Host:  Dirk Grunwald
------------------------------
http://www.cs.colorado.edu/department/events/colloquia/colloquia.html

Sign Language Interpreters Available Upon Request.  Please contact Jane 
Obrecht, Department of
Computer Science, Engineering  ECOT 722, 303-492-6101, at least five days 
prior to the colloquium.

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