Difference between pages "DiskExplorer" and "HFS+"

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HFS+, or Hierarchical File System Plus, is the file system designed by Apple Computer[http://www.apple.com] to supersede HFS. First introduced with Mac OS 8.1, one of the biggest differences was the lower allocation block size of 4kb, thereby increasing performance and lowering fragmentation [http://developer.apple.com/technotes/tn/tn1121.html#HFSPlus].
 +
 
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There are structurally many differences between HFS and HFS+, which are listed below[http://developer.apple.com/technotes/tn/tn1150.html#HFSPlusBasics]:
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<CENTER><TABLE Border=1 cellpadding=2 cellspacing=0>
 +
            <TR>
 +
              <TD>
 +
                  <P><B>Feature</B></p>
 +
 
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              </TD><TD>
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                  <P><B>HFS</B></p>
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              </TD><TD>
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                  <P><B>HFS Plus</B></p>
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              </TD><TD>
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                  <P><B>Benefit/Comment</B></p>
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              </TD></TR>
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 +
            <TR>
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              <TD>
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                  <P>User visible name</p>
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              </TD><TD>
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                  <P>Mac OS Standard</p>
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              </TD><TD>
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                  <P>Mac OS Extended</p>
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              </TD><TD>
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                  <P></p>
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              </TD></TR>
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            <TR>
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              <TD>
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                  <P>Number of allocation blocks</p>
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              </TD><TD>
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                  <P>16 bits worth</p>
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              </TD><TD>
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                  <P>32 bits worth</p>
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              </TD><TD>
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                  <P>Radical decrease in disk space used on large
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                  volumes, and a larger number of files per volume.</p>
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              </TD></TR>
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            <TR>
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              <TD>
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                  <P>Long file names</p>
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              </TD><TD>
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                  <P>31 characters</p>
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              </TD><TD>
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                  <P>255 characters</p>
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              </TD><TD>
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                  <P>Obvious user benefit; also improves
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                  cross-platform compatibility</p>
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              </TD></TR>
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            <TR>
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              <TD>
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                  <P>File name encoding</p>
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              </TD><TD>
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                  <P>MacRoman</p>
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              </TD><TD>
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                  <P>Unicode</p>
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              </TD><TD>
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                  <P>Allows for international-friendly file names,
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                  including mixed script names</p>
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              </TD></TR>
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            <TR>
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              <TD>
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                  <P>File/folder attributes</p>
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              </TD><TD>
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                  <P>Support for fixed size attributes (FileInfo and
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                  ExtendedFileInfo)</p>
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              </TD><TD>
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                  <P>Allows for future meta-data extensions</p>
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              </TD><TD>
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                  <P>Future systems may use metadata for a richer
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                  Finder experience</p>
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              </TD></TR>
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            <TR>
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              <TD>
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                  <P>OS startup support</p>
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              </TD><TD>
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                  <P>System Folder ID</p>
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              </TD><TD>
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                  <P>Also supports a dedicated startup file</p>
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              </TD><TD>
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                  <P>May help non-Mac OS systems to boot from HFS
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                  Plus volumes</p>
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              </TD></TR>
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            <TR>
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              <TD>
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                  <P>catalog node size</p>
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              </TD><TD>
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                  <P>512 bytes</p>
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              </TD><TD>
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                  <P>4 KB</p>
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 +
              </TD><TD>
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                  <P>Maintains efficiency in the face of the other
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                  changes. (This larger catalog node size is due to
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                  the much longer file names [512 bytes as opposed to
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                  32 bytes], and larger catalog records (because of
 +
                  more/larger fields)).</p>
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              </TD></TR>
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            <TR>
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              <TD>
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                  <P>Maximum file size</p>
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              </TD><TD>
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                  <P>2<SUP>31</SUP> bytes</p>
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              </TD><TD>
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                  <P>2<SUP>63</SUP> bytes</p>
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              </TD><TD>
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                  <P>Obvious user benefit, especially for multimedia
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                  content creators.</p></td>
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                  </tr>
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</table></CENTER>
 +
<br>
 +
An HFS+ volume contains five special files that are necessary to the file system:
 +
<nl>
 +
<li>
 +
Catalog file
 +
</li>
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<li>Extents overflow file
 +
</li>
 +
<li>
 +
Allocation file
 +
</li>
 +
<li>Attributes file
 +
</li>
 +
<li>
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Startup file
 +
</li>
 +
</nl>

Revision as of 18:37, 28 November 2006

HFS+, or Hierarchical File System Plus, is the file system designed by Apple Computer[1] to supersede HFS. First introduced with Mac OS 8.1, one of the biggest differences was the lower allocation block size of 4kb, thereby increasing performance and lowering fragmentation [2].

There are structurally many differences between HFS and HFS+, which are listed below[3]:

Feature

HFS

HFS Plus

Benefit/Comment

User visible name

Mac OS Standard

Mac OS Extended

Number of allocation blocks

16 bits worth

32 bits worth

Radical decrease in disk space used on large volumes, and a larger number of files per volume.

Long file names

31 characters

255 characters

Obvious user benefit; also improves cross-platform compatibility

File name encoding

MacRoman

Unicode

Allows for international-friendly file names, including mixed script names

File/folder attributes

Support for fixed size attributes (FileInfo and ExtendedFileInfo)

Allows for future meta-data extensions

Future systems may use metadata for a richer Finder experience

OS startup support

System Folder ID

Also supports a dedicated startup file

May help non-Mac OS systems to boot from HFS Plus volumes

catalog node size

512 bytes

4 KB

Maintains efficiency in the face of the other changes. (This larger catalog node size is due to the much longer file names [512 bytes as opposed to 32 bytes], and larger catalog records (because of more/larger fields)).

Maximum file size

231 bytes

263 bytes

Obvious user benefit, especially for multimedia content creators.


An HFS+ volume contains five special files that are necessary to the file system: <nl>

  • Catalog file
  • Extents overflow file
  • Allocation file
  • Attributes file
  • Startup file
  • </nl>