glossary.html

这是NTFS文件0.5版本技术文件

      <dd><a name="sdh"></a></dd>
      <dt>$SDH</dt>
        <dd>
        This is one of the named indexes belonging to $Secure.
        <br>See also:
        <a href="#index">Index</a>,
        <a href="#sii">$SII</a> and
        <a href="#secure">$Secure</a>.
        </dd>

      <dd><a name="sds"></a></dd>
      <dt>$SDS</dt>
        <dd>
        This is the named data stream belonging to $Secure.
        <br>See also:
        <a href="#secure">$Secure</a> and
        <a href="#stream">Stream</a>
        </dd>

      <dd><a name="sector"></a></dd>
      <dt>Sector</dt>
        <dd>
        Unit of data on the physical storage unit. The storage controller
        can only access data in multiples of this unit. A sector is usually 512
        bytes, but can be 1 KB on certain Asian hard disks.
        </dd>

      <dd><a name="secure"></a></dd>
      <dt>$Secure <a href="../files/secure.html">(More...) </a></dt>
        <dd>
        This <a href="#metadata">metadata</a> file stores a table of security
        descriptors used by the volume.
        </dd>

      <dd><a name="security"></a></dd>
      <dt>Security</dt>
        <dd>
        There are two levels of security in NTFS.
        There are the DOS File Permissions, such as <q>Read Only</q> and <q>Hidden</q>
        and an ACL model which grants specific permissions to specific users.
        <br>See also:
        <a href="#ace">ACE</a>,
        <a href="#acl">ACL</a>,
        <a href="#permissions">Permissions</a>,
        <a href="#security_descriptor">$SECURITY_DESCRIPTOR</a> and
        <a href="#sid">SID</a>.
        </dd>

      <dd><a name="security_descriptor"></a></dd>
      <dt>$SECURITY_DESCRIPTOR <a href="../attributes/security_descriptor.html">(More...) </a></dt>
        <dd>
        This attribute stores all the security information about a file or
        directory.  It contains an ACL for auditing, an ACL for permissions and
        a SID to show the user and group of the owner.
        <br>See also:
        <a href="#attribute">Attribute</a>,
        <a href="#acl">ACL</a>,
        <a href="#ace">ACE</a> and
        <a href="#sid">SID</a>.
        </dd>

      <dd><a name="sid"></a></dd>
      <dt>Security Identifier (SID)</dt>
        <dd>
        This variable-length identifier uniquely identifies a user
        or a group on an NT domain.  It is used in the security permissions.
        <br>See also:
        <a href="#ace">ACE</a>,
        <a href="#acl">ACL</a> and
        <a href="#security_descriptor">$SECURITY_DESCRIPTOR</a>.
        </dd>

      <dd><a name="sequence_array"></a></dd>
      <dt>Sequence Array <a href="#sid">(See Update Sequence)</a></dt>

      <dt>SID <a href="#sid">(See Security Identifier)</a></dt>

      <dd><a name="sii"></a></dd>
      <dt>$SII</dt>
        <dd>
        This is one of the named indexes belonging to $Secure.
        <br>See also:
        <a href="#index">Index</a>,
        <a href="#sdh">$SDH</a> and
        <a href="#secure">$Secure</a>.
        </dd>

      <dd><a name="sparse_file"></a></dd>
      <dt>Sparse File</dt>
        <dd>
        NTFS supports sparse files.  If a file contains large, contiguous,
        blocks of zeros, then NTFS can choose to not waste any space storing
        these portions on disk.  They are represented as data runs containing
        nothing.  When read from disk, NTFS simply substitutes zeros.
        <br>See also:
        <a href="#data_runs">Data Runs</a>.
        </dd>

      <dd><a name="standard_information"></a></dd>
      <dt>$STANDARD_INFORMATION <a href="../attributes/standard_information.html">(More...) </a></dt>
        <dd>
        This <a href="#attribute">attribute</a> contains information about a file,
        such as its file permissions and when it was created.
        </dd>

      <dd><a name="stream"></a></dd>
      <dt>Stream</dt>
        <dd>
        All data on NTFS is stored in streams, which can have names.
        A file can have more than one data streams,
        but exactly one must have no name.
        The <q>size</q> of a file is the size of its unnamed data attribute.
        </dd>

      <dd><a name="symbolic_link"></a></dd>
      <dt>$SYMBOLIC_LINK</dt>
        <dd>
        This <a href="#attribute">attribute</a>
        This attribute, like <a href="#volume_version">$VOLUME_VERSION</a>
        existed in NTFS v1.2, but wasn't used.
        It does not longer exist in NTFS v3.0+.
        </dd>
    </dl>

    <hr>

    <dl>
      <dd><a name="t"></a></dd>

      <dd><a name="tb"></a></dd>
      <dt>TB <a href="#units">(See Units)</a></dt>

      <dd><a name="time_stamp"></a></dd>
      <dt>Time Stamp</dt>
        <dd>
        NTFS stores four significant times referring to files and directories.
        They are: File creation time; Last modification time; Last modification
        of the MFT record; Last access time.  NTFS stores dates as the number
        of 100ns units since Jan&nbsp;1<sup>st</sup>&nbsp;1601.
        Unix, stores dates as the number of seconds since Jan&nbsp;1<sup>st</sup>&nbsp;1970.
        <pre>
	standardise 4 time fields name &amp; description concept page?
	refer to 4 times as:
	  C creation
	  A alter (modification)
	  M mft (mft changed) 
	  R read (last access)
		  
        FIXME:
        NOTE: There is conflicting information about the meaning of each of the time
        fields but the meaning as defined below has been verified to be
        correct by practical experimentation on Windows NT4 SP6a and is hence
        assumed to be the one and only correct interpretation.

        creation_time
	Time file was created. Updated when a filename is changed(?).

        last_data_change_time
	Time the data attribute was last modified.

        last_mft_change_time
	Time this mft record was last modified.

        last_access_time
	Approximate time when the file was last accessed (obviously this is not
	updated on read-only volumes). In Windows this is only updated when
	accessed if some time delta has passed since the last update.
        </pre>
	<pre>
	N.B. There is conflicting information about the meaning of each of the time
	fields but the meaning as defined below has been verified to be
	correct by practical experimentation on Windows NT4 SP6a and is hence
	assumed to be the one and only correct interpretation.
	</pre>

        <br>See also:
        <a href="#file_record">File Record</a>
        </dd>

      <dd><a name="transaction"></a></dd>
      <dt>Transaction</dt>
        <dd>
        A transaction on a system is a set of operations (on that
        system) that constitutes a unit. This unit can't be divided.  Before the
        transaction, the state of the system is well defined. During the
        transaction, it is undefined. After the transaction, it is well defined
        again. A transaction can't be half-realized: if no operation fails, the
        transaction is realized. If on the contrary an error occurs in one or
        more of the operations, the transaction is not realized. A set of (even
        atomic) operations is not atomic by definition. A transaction is a model
        that provides a kind of atomicity to this set of operations.
        </dd>
    </dl>

    <hr>

    <dl>
      <dd><a name="u"></a></dd>

      <dd><a name="unfragmented"></a></dd>
      <dt>Unfragmented <a href="#fragmented">(see Fragmented)</a></dt>

      <dd><a name="unicode"></a></dd>
      <dt>Unicode</dt>
        <dd>
        International character set coded on 16 bits (ASCII is coded on
        7 bits and Latin-1 coded on 8 bits). Unicode can represent every symbol
        of almost every language in the world.
        </dd>

      <dd><a name="units"></a></dd>
      <dt>Units</dt>
        <dd>
        Every size in this document is measured in bytes (unless clearly marked).
        The abbreviations for sizes are:
        <br><br>

        <table border="1" summary="" cellspacing="0">
          <tr>
            <th>Abbr.</th>
            <th>Name</th>
            <th class="numeric">Exactly</th>
            <th class="numeric">Approx.</th>
          </tr>
          <tr>
            <td>KB</td>
            <td>Kilobyte</td>
            <td class="numeric">2<sup>10</sup></td>
            <td class="numeric">10<sup>3</sup></td>
          </tr>
          <tr>
            <td>MB</td>
            <td>Megabyte</td>
            <td class="numeric">2<sup>20</sup></td>
            <td class="numeric">10<sup>6</sup></td>
          </tr>
          <tr>
            <td>GB</td>
            <td>Gigabyte</td>
            <td class="numeric">2<sup>30</sup></td>
            <td class="numeric">10<sup>9</sup></td>
          </tr>
          <tr>
            <td>TB</td>
            <td>Terabyte</td>
            <td class="numeric">2<sup>40</sup></td>
            <td class="numeric">10<sup>12</sup></td>
          </tr>
        </table>

        <br>
	<pre>see also Binary, Decimal, Hexadecimal</pre>

        N.B. Technically, the correct abbreviation for 1024 bytes
        is KiB, which stands for kilobinary bytes.
        </dd>

      <dd><a name="upcase"></a></dd>
      <dt>$UpCase <a href="../files/upcase.html">(More...) </a></dt>
        <dd>
        This <a href="#metadata">metadata</a> file contains 128KB of capital
        letters. For each character in the Unicode alphabet, there
        is an entry in this file. It is used to compare and sort filenames.
        </dd>

      <dd><a name="update_sequence"></a></dd>
      <dt>Update Sequence</dt>
        <dd>
        Several structures in NTFS have sequence numbers in them
        to check for consistancy errors.  They are FILE, INDX, RCRD
        and RSTR records.  Before the record is written to disk,
        the last two bytes of each sector are copied to an array
        in the header.  The update sequence number is then
        incremented and written to the end of each sector.  If
        any disk corruption occurs, this technique could detect it.

        <pre>
        The Update Sequence Array (usa) is an array of the __u16 values which belong
        to the end of each sector protected by the update sequence record in which
        this array is contained. Note that the first entry is the Update Sequence
        Number (usn), a cyclic counter of how many times the protected record has
        been written to disk. The values 0 and -1 (ie. 0xffff) are not used. All
        last __u16's of each sector have to be equal to the usn (during reading) or
        are set to it (during writing). If they are not, an incomplete multi sector
        transfer has occured when the data was written.
        The maximum size for the update sequence array is fixed to:
                maximum size = usa_ofs + (usa_count * 2) = 510 bytes
        The 510 bytes comes from the fact that the last __u16 in the array has to
        (obviously) finish before the last __u16 of the first 512-byte sector.
        This formula can be used as a consistency check in that usa_ofs +
        (usa_count * 2) has to be less than or equal to 510.
        </pre>

        <br>See also:
        <a href="#file_record">FILE Record</a>
        <a href="#indx_record">INDX Record</a>
        <a href="#rcrd_record">RCRD Record</a>
        <a href="#rstr_record">RSTR Record</a>
        </dd>

      <dd><a name="usnjrnl"></a></dd>
      <dt>$UsnJrnl <a href="../files/usnjrnl.html">(More...) </a></dt>
        <dd>
	<pre>used for logging</pre>
        </dd>
    </dl>

    <hr>

    <dl>
      <dd><a name="v"></a></dd>

      <dd><a name="vcn"></a></dd>
      <dt>VCN <a href="#vcn">(See Virtual Cluster Number)</a></dt>

      <dt>Virtual Cluster Number (VCN)</dt>
        <dd>
        When representing the data runs of a file, the clusters
        are given virtual cluster numbers.  Cluster zero refers
        to the first cluster of the file.  The data runs map the
        VCNs to LCNs so that the file can be located on the volume.
        <br>See also:
        <a href="#cluster">Cluster</a>,
        <a href="#lcn">LCN</a> and
        <a href="#volume">Volume</a>.
        </dd>

      <dd><a name="volume"></a></dd>
      <dt>Volume</dt>
        <dd>
        (=drive=partition) (extended, striped, mirrored (not supported))
        A logical NTFS partition. It is a group of physical partitions
        (see the fdisk utility, you can set up mirroring and stripping) that act
        as one (somewhat like the Linux md block devices).
        </dd>

      <dt>$Volume <a href="../files/volume.html">(More...) </a></dt>
        <dd>
        This <a href="#metadata">metadata</a> file contains information
        such as the name, serial number and whether the volume needs
        checking for errors.
        </dd>

      <dd><a name="volume_information"></a></dd>
      <dt>$VOLUME_INFORMATION <a href="../attributes/volume_information.html">(More...) </a></dt>
        <dd>
        This <a href="#attribute">attribute</a> contains information
        such as the serial number, creation time and whether the volume
        needs checking for errors.
        </dd>

      <dd><a name="volume_name"></a></dd>
      <dt>$VOLUME_NAME <a href="../attributes/volume_name.html">(More...) </a></dt>
        <dd>
        This <a href="#attribute">attribute</a> stores the name of the
        volume in Unicode.
        </dd>

      <dd><a name="volume_version"></a></dd>
      <dt>$VOLUME_VERSION</dt>
        <dd>
        This <a href="#attribute">attribute</a>
        This attribute, like <a href="#symbolic_link">$SYMBOLIC_LINK</a>
        existed in NTFS v1.2, but wasn't used.
        It does not longer exist in NTFS v3.0+.
        </dd>

      <dd><a name="w"></a></dd>
      <dd><a name="x"></a></dd>
      <dd><a name="y"></a></dd>
      <dd><a name="z"></a></dd>
    </dl>

    <br>
    <a class="contact" href="http://linux-ntfs.sourceforge.net/ntfs/help/glossary.html">Online</a>
    <!-- The two validators will only work if this page is visible on the web -->
    <a class="contact" href="http://validator.w3.org/check/referer">Validate HTML</a>
    <a class="contact" href="http://jigsaw.w3.org/css-validator/check/referer">Validate CSS</a>
    <a class="contact" href="mailto:[e-mail]">$Id: glossary.html,v 1.13 2001/07/11 17:09:23 flatcap Exp $</a>
  </body>
</html>