Attachment 59777 Details for Bug 89900 – file.diff

[patch] file.diff

file.diff (text/plain), 3.69 KB, created by Lowell Gilbert on 2005-12-03 22:20:02 UTC

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Creator: Lowell Gilbert

Created: 2005-12-03 22:20:02 UTC

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>--- en_US.ISO8859-1/books/handbook/disks/chapter.sgml.ORIG	Fri Aug  5 15:06:20 2005
>+++ en_US.ISO8859-1/books/handbook/disks/chapter.sgml	Sat Dec  3 16:03:31 2005
>@@ -2269,8 +2269,103 @@
> 	restore it, even if you have not asked it to!</para>
>     </sect2>
>   </sect1>
> 
>+  <sect1 id="backup-strategies">
>+    <title>Backup Strategies</title>
>+
>+        <para>  
>+	The first requirement in devising a backup plan is to make sure that all of the
>+	following problems are covered:
>+	<itemizedlist>
>+	  <listitem>
>+	    <para>
>+	      disk failure
>+	    </para>
>+	  </listitem>
>+	  <listitem>
>+	    <para>
>+	      accidental file deletion
>+	    </para>
>+	  </listitem>
>+	  <listitem>
>+	    <para>
>+	      random file corruption
>+	    </para>
>+	  </listitem>
>+	  <listitem>
>+	    <para>
>+  	      complete machine destruction (e.g., fire) including destruction of any on-site backups
>+	    </para>
>+	  </listitem>
>+	</itemizedlist></para>
>+
>+	<para>It is perfectly possible that some systems will be best served by
>+	having each of these problems covered by a completely different
>+	technique.  Except for strictly personal systems with very low-value
>+	data, it is unlikely that one technique would cover all of them.</para>
>+
>+	<para>Some of the techniques in the toolbox are:</para>
>+	  <itemizedlist>
>+	    <listitem>
>+	      <para>archives of the whole system, backed up onto permanent media
>+		offsite.  This actually provides protection against all of the
>+		possible problems listed above, but is slow and inconvenient to
>+		restore from.  You can keep copies of the backups onsite and/or
>+		online, but there will still be inconveniences in restoring files,
>+		especially for non-privileged users.</para>
>+	    </listitem>
>+
>+	    <listitem>
>+	      <para>filesystem snapshots.  This is really only helpful in the
>+	        accidental file deletion scenario, but it can be
>+		<emphasis>very</emphasis> helpful
>+	        in that case, and is quick and easy to deal with.</para>
>+	    </listitem>
>+
>+	    <listitem>
>+
>+	      <para> copies of whole filesystems and/or disks.  [for example,
>+	      	periodic rsync of the whole machine] This is generally most
>+	      	useful in networks with unique requirements.  For general
>+	      	protection against disk failure, it is usually inferior to
>+	      	<acronym>RAID</acronym>.  For restoring accidentally deleted
>+	      	files, it can be comparable to <acronym>UFS</acronym>
>+	      	snapshots, but that depends on your preferences.</para>
>+
>+	    </listitem>
>+
>+	    <listitem>
>+
>+	      <para><acronym>RAID</acronym>.  Minimizes or avoids downtime
>+	        when a disk fails.  At the expense of having to deal with disk
>+	        failures more often (because you have more disks), albeit at a
>+	        much lower urgency.</para>
>+
>+	    </listitem>
>+
>+	    <listitem>
>+
>+	      <para>checking fingerprints of files.  The
>+	        &man.mtree.8;
>+		program is very useful for this.  Although it is not a backup
>+		technique, it helps guarantee that you will notice when you need
>+		to resort to your backups.  This is particularly important for
>+		offline backups, and should be checked periodically.
>+
>+	    </listitem>
>+    	  </itemizedlist>
>+
>+	<para>It is quite easy to come up with even more techniques, many of them
>+	  variations on the ones listed above.  Specialized requirements will
>+	  usually lead to specialized techniques (for example, backing up a live
>+	  database usually requires a method particular to the database
>+	  software as an intermediate step).  The important thing is to know
>+	  what dangers you want to protect against, and how you will handle
>+	  each.</para>
>+
>+  </sect1>
>+
>   <sect1 id="backup-basics">
>     <title>Backup Basics</title>
> 
>     <para>The three major backup programs are

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