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Disk management for a hard real-time file system Cheng , Raymond Man Kit
Abstract
The problem of scheduling disk requests in a personal hard real-time read/write file system is examined. It is shown that any optimal algorithm for a simplified disk scheduling can be forced to thrash very badly. To avoid thrashing, we propose a fixed-period scan (FSCAN), approach for disk scheduling in our file system. The idea is to use the CSCAN policy to pick up the data blocks requested by a periodic preemptive schedule. The approach trades disk block size and memory buffer size for higher performance. We derive the worst case seek and rotational overhead for the FSCAN algorithm, and we show that the worst-case seek overhead can be measured empirically for a large class of seek functions. Using this approach and utilizing measured seek functions from real disk drives, we show that these policies can transfer data at 40-70% of the maximum transfer rate of modern disk drives, depending on the file system parameters. A configuration program is developed to automatically test and configure the FSCAN algorithm for modern hard disks. The design, implementation and testing of this program are described.
Item Metadata
Title |
Disk management for a hard real-time file system
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Creator | |
Publisher |
University of British Columbia
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Date Issued |
1995
|
Description |
The problem of scheduling disk requests in a personal hard real-time
read/write file system is examined. It is shown that any optimal algorithm for a
simplified disk scheduling can be forced to thrash very badly. To avoid
thrashing, we propose a fixed-period scan (FSCAN), approach for disk scheduling
in our file system. The idea is to use the CSCAN policy to pick up the data
blocks requested by a periodic preemptive schedule. The approach trades disk
block size and memory buffer size for higher performance. We derive the worst case
seek and rotational overhead for the FSCAN algorithm, and we show that
the worst-case seek overhead can be measured empirically for a large class of
seek functions. Using this approach and utilizing measured seek functions from
real disk drives, we show that these policies can transfer data at 40-70% of the
maximum transfer rate of modern disk drives, depending on the file system
parameters. A configuration program is developed to automatically test and
configure the FSCAN algorithm for modern hard disks. The design,
implementation and testing of this program are described.
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Extent |
3751826 bytes
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Genre | |
Type | |
File Format |
application/pdf
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Language |
eng
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Date Available |
2009-01-31
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Provider |
Vancouver : University of British Columbia Library
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Rights |
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.
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DOI |
10.14288/1.0065189
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URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
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Graduation Date |
1995-11
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Campus | |
Scholarly Level |
Graduate
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Aggregated Source Repository |
DSpace
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Item Media
Item Citations and Data
Rights
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.