- is the number of files to be stored in the file system. This determines
- the number of inodes needed, which drives the MDT sizing. To be on the
- safe side, plan for 2 KB per ldiskfs inode on the MDT, which is the
- default value. Attached storage required for Lustre file system metadata
- is typically 1-2 percent of the file system capacity depending upon
- file size.</para>
- <note condition='l24'><para>Starting in release 2.4, using the DNE
- remote directory feature it is possible to increase the metadata
- capacity of a single filesystem by configuring additional MDTs into
- the filesystem, see <xref linkend="dbdoclet.addingamdt"/> for details.
- </para></note>
- <para>For example, if the average file size is 5 MB and you have
- 100 TB of usable OST space, then you can calculate the minimum number
- of inodes as follows:</para>
+ is the number of files to be stored in the file system, which depends on
+ at least 4 KiB per inode of usable space on the MDT. Since MDTs typically
+ use RAID-1+0 mirroring, the total storage needed will be double this.
+ </para>
+ <para>Please note that the actual used space per MDT depends on the number
+ of files per directory, the number of stripes per file, whether files
+ have ACLs or user xattrs, and the number of hard links per file. The
+ storage required for Lustre file system metadata is typically 1-2
+ percent of the total file system capacity depending upon file size.</para>
+ <para>For example, if the average file size is 5 MiB and you have
+ 100 TiB of usable OST space, then you can calculate the minimum total
+ number of inodes each for MDTs and OSTs as follows:</para>