| Summary: | 博士 === 國立交通大學 === 資訊科學學系 === 84 === Due to the increasing gap between CPU and disk I/O speeds, file
system is becoming the performance bottle-neck in computer
system design. There are two types of entities in a file
system: data and metadata. Data mean the actual contents of
files. Metadata include access control and other descriptive
about files. Previous research indicates that metadata writes
account for 38-40% of disk I/O operations. We propose the
design and implementation of a metadata ordering mechanism and
its corresponding asynchronous write facility. With such a
facility, we can eliminate large numbers of synchronous
metadata writes, and have the flexibility of choosing a better
way to these metadata modifications to disk asynchronously.
Extensive performance evaluation shows that substantial
performance improvement can be achieved under various
benchmarks. Delayed write is a technique to improve the file
system performance of UNIX operating systems. When write
operations are delayed, an update policy decides how and when
to write modified blocks to their assigned disk locations.
Recent results show that conventional update mechanisms neglect
the fact that different I/O requests naturally have different
It makes time critical interactive jobs endure large variations
response time. Update policy controls background write that are
less time critical and should be performed under that do not
violate the urgency of other time criti-cal jobs. In this
thesis we also propose an effective update scheme. suggest new
techniques : burst declustering and opportunistic asynchronous
write. Besides, we develop a system activity sensor called
SAPRO (system activity probe) that monitors the system
activities and disk queuing status to adjust the behavior of
our algorithm. Performance evaluation shows that our al-gorithm
can alleviate the lengthy queuing delay, reduce the variance
and case read response time significantly (40% and 90% The mean
read response time and total system performance are also
improved
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