- <section xml:id="dbdoclet.50438207_56395">
- <title>
- <indexterm><primary>backup</primary></indexterm>
- <indexterm><primary>restoring</primary><see>backup</see></indexterm>
- <indexterm><primary>LVM</primary><see>backup</see></indexterm>
- <indexterm><primary>rsync</primary><see>backup</see></indexterm>
- Backing up a File System</title>
- <para>Backing up a complete file system gives you full control over the files to back up, and
- allows restoration of individual files as needed. File system-level backups are also the
- easiest to integrate into existing backup solutions.</para>
- <para>File system backups are performed from a Lustre client (or many clients working parallel in different directories) rather than on individual server nodes; this is no different than backing up any other file system.</para>
- <para>However, due to the large size of most Lustre file systems, it is not always possible to get a complete backup. We recommend that you back up subsets of a file system. This includes subdirectories of the entire file system, filesets for a single user, files incremented by date, and so on.</para>
+ <para>It is <emphasis>strongly</emphasis> recommended that sites perform
+ periodic device-level backup of the MDT(s)
+ (<xref linkend="backup_device"/>),
+ for example twice a week with alternate backups going to a separate
+ device, even if there is not enough capacity to do a full backup of all
+ of the filesystem data. Even if there are separate file-level backups of
+ some or all files in the filesystem, having a device-level backup of the
+ MDT can be very useful in case of MDT failure or corruption. Being able to
+ restore a device-level MDT backup can avoid the significantly longer process
+ of restoring the entire filesystem from backup. Since the MDT is required
+ for access to all files, its loss would otherwise force full restore of the
+ filesystem (if that is even possible) even if the OSTs are still OK.</para>
+ <para>Performing a periodic device-level MDT backup can be done relatively
+ inexpensively because the storage need only be connected to the primary
+ MDS (it can be manually connected to the backup MDS in the rare case
+ it is needed), and only needs good linear read/write performance. While
+ the device-level MDT backup is not useful for restoring individual files,
+ it is most efficient to handle the case of MDT failure or corruption.</para>
+ <section xml:id="backup_file">
+ <title>
+ <indexterm>
+ <primary>backup</primary>
+ </indexterm>
+ <indexterm>
+ <primary>restoring</primary>
+ <see>backup</see>
+ </indexterm>
+ <indexterm>
+ <primary>LVM</primary>
+ <see>backup</see>
+ </indexterm>
+ <indexterm>
+ <primary>rsync</primary>
+ <see>backup</see>
+ </indexterm>Backing up a File System</title>
+ <para>Backing up a complete file system gives you full control over the
+ files to back up, and allows restoration of individual files as needed.
+ File system-level backups are also the easiest to integrate into existing
+ backup solutions.</para>
+ <para>File system backups are performed from a Lustre client (or many
+ clients working parallel in different directories) rather than on
+ individual server nodes; this is no different than backing up any other
+ file system.</para>
+ <para>However, due to the large size of most Lustre file systems, it is
+ not always possible to get a complete backup. We recommend that you back
+ up subsets of a file system. This includes subdirectories of the entire
+ file system, filesets for a single user, files incremented by date, and
+ so on, so that restores can be done more efficiently.</para>