Browse Prior Art Database

Tool to Examine the Efficiency of File Placement On Disk

IP.com Disclosure Number: IPCOM000122020D
Original Publication Date: 1991-Oct-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 2 page(s) / 82K

Publishing Venue

IBM

Related People

Smith, MG: AUTHOR

Abstract

Disclosed is a program which displays the placement of a data file's blocks on disk storage and measures the efficiency of that placement. Variable-size data files in AIX* and other UNIX** operating systems are stored as a sequence of blocks. (The last block may only be partially filled.) Even though the sequence of blocks represents a logically contiguous data space, the blocks may not necessarily be stored contiguously on disk. The mapping of the logically contiguous file space to disk is usually hidden from users.

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Tool to Examine the Efficiency of File Placement On Disk

      Disclosed is a program which displays the placement of a
data file's blocks on disk storage and measures the efficiency of
that placement.  Variable-size data files in AIX* and other UNIX**
operating systems are stored as a sequence of blocks.  (The last
block may only be partially filled.)  Even though the sequence of
blocks represents a logically contiguous data space, the blocks may
not necessarily be stored contiguously on disk.  The mapping of the
logically contiguous file space to disk is usually hidden from users.

      When retrieving data from the file, the physical placement of
the file blocks will determine the efficiency (performance) of the
retrieval. The disclosed program (called "fileplace") discovers and
displays the mapping  of the file to physical disk blocks and
computes one or more measures of efficiency for the file's placement.
The tool can be used to explain current access performance to a file
and provides insight on how the file placement might be changed for
better retrieval performance.
 PROGRAM FEATURES

      This program has the following unique features.  We are not
aware of any tools for UNIX operating systems which have these
features.
     1) The program displays (in either tabular or graphical form)
the placement of file blocks at each level of storage abstraction.
For example, if a file system is stored on a logical "disk" which is
distributed among one or more physical disks, the program will
display the placement of file blocks within the logical disk and
display the placement of file blocks among the physical disks which
implement the logical disk.
     2) The program displays the placement of each copy of the file,
if the file system stores multiple copies of each file for improved
data availability.
     3) The program displays the placement of any "meta data" (e.g.,
storage maps) associated with the file which may be accessed along
with the file data blocks.
     4) The program calculates a...