- MDTs). This change enabled future support for multiple MDTs (introduced in
- Lustre software release 2.4) and ZFS (introduced in Lustre software release
- 2.4).</para>
- <para>Also introduced in release 2.0 is an ldiskfs feature named
- <emphasis role="italic">FID-in-dirent</emphasis>(also known as
- <emphasis role="italic">dirdata</emphasis>) in which the FID is stored as
- part of the name of the file in the parent directory. This feature
- significantly improves performance for
- <literal>ls</literal> command executions by reducing disk I/O. The
- FID-in-dirent is generated at the time the file is created.</para>
- <note>
- <para>The FID-in-dirent feature is not backward compatible with the
- release 1.8 ldiskfs disk format. Therefore, when an upgrade from
- release 1.8 to release 2.x is performed, the FID-in-dirent feature is
- not automatically enabled. For upgrades from release 1.8 to releases
- 2.0 through 2.3, FID-in-dirent can be enabled manually but only takes
- effect for new files.</para>
- <para>For more information about upgrading from Lustre software release
- 1.8 and enabling FID-in-dirent for existing files, see
- <xref xmlns:xlink="http://www.w3.org/1999/xlink"
- linkend="upgradinglustre" />Chapter 16 “Upgrading a Lustre File
- System”.</para>
- </note>
- <para condition="l24">The LFSCK file system consistency checking tool
- released with Lustre software release 2.4 provides functionality that
- enables FID-in-dirent for existing files. It includes the following
- functionality:
+ MDTs). This allows multiple MDTs and OSTs to uniquely identify objects
+ without depending on identifiers in the underlying filesystem (e.g. inode
+ numbers) that are likely to be duplicated between targets. The FID SEQ
+ number also allows mapping a FID to a particular MDT or OST.</para>
+ <para>The LFSCK file system consistency checking tool provides
+ functionality that enables FID-in-dirent for existing files. It
+ includes the following functionality: