Date: Fri, 11 Apr 2014 15:47:38 +0000 (UTC) From: Dru Lavigne <dru@FreeBSD.org> To: doc-committers@freebsd.org, svn-doc-all@freebsd.org, svn-doc-head@freebsd.org Subject: svn commit: r44531 - head/en_US.ISO8859-1/books/handbook/geom Message-ID: <201404111547.s3BFlccV011871@svn.freebsd.org>
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Author: dru Date: Fri Apr 11 15:47:38 2014 New Revision: 44531 URL: http://svnweb.freebsd.org/changeset/doc/44531 Log: Editorial review of Synopsis/Introduction and RAID0 sections. Sponsored by: iXsystems Modified: head/en_US.ISO8859-1/books/handbook/geom/chapter.xml Modified: head/en_US.ISO8859-1/books/handbook/geom/chapter.xml ============================================================================== --- head/en_US.ISO8859-1/books/handbook/geom/chapter.xml Fri Apr 11 14:00:48 2014 (r44530) +++ head/en_US.ISO8859-1/books/handbook/geom/chapter.xml Fri Apr 11 15:47:38 2014 (r44531) @@ -26,31 +26,34 @@ <title>Synopsis</title> <indexterm> - <primary>GEOM</primary> + <primary><acronym>GEOM</acronym></primary> </indexterm> <indexterm> - <primary>GEOM Disk Framework</primary> - <see>GEOM</see> + <primary><acronym>GEOM</acronym> Disk Framework</primary> + <see><acronym>GEOM</acronym></see> </indexterm> - <para>This chapter covers the use of disks under the GEOM - framework in &os;. This includes the major <acronym - role="Redundant Array of Inexpensive Disks">RAID</acronym> + <para>In &os;, the <acronym>GEOM</acronym> framework permits access and control to classes, such as Master + Boot Records and <acronym>BSD</acronym> labels, through the use + of providers, or the disk devices in <filename>/dev</filename>. + By supporting various software <acronym>RAID</acronym> + configurations, <acronym>GEOM</acronym> transparently provides access to the + operating system and operating system utilities.</para> + + <para>This chapter covers the use of disks under the <acronym>GEOM</acronym> + framework in &os;. This includes the major <acronym>RAID</acronym> control utilities which use the framework for configuration. - This chapter will not go into in depth discussion on how GEOM - handles or controls I/O, the underlying subsystem, or code. - This information is provided in &man.geom.4; and its various - <literal>SEE ALSO</literal> references. This chapter is also + This chapter is not a definitive guide to <acronym>RAID</acronym> configurations - and only GEOM-supported <acronym>RAID</acronym> classifications - will be discussed.</para> + and only <acronym>GEOM</acronym>-supported <acronym>RAID</acronym> classifications + are discussed.</para> <para>After reading this chapter, you will know:</para> <itemizedlist> <listitem> <para>What type of <acronym>RAID</acronym> support is - available through GEOM.</para> + available through <acronym>GEOM</acronym>.</para> </listitem> <listitem> @@ -61,11 +64,11 @@ <listitem> <para>How to mirror, stripe, encrypt, and remotely connect - disk devices through GEOM.</para> + disk devices through <acronym>GEOM</acronym>.</para> </listitem> <listitem> - <para>How to troubleshoot disks attached to the GEOM + <para>How to troubleshoot disks attached to the <acronym>GEOM</acronym> framework.</para> </listitem> </itemizedlist> @@ -74,28 +77,17 @@ <itemizedlist> <listitem> - <para>Understand how &os; treats <link linkend="disks">disk - devices</link>.</para> + <para>Understand how &os; treats disk devices (<xref + linkend="disks"/>).</para> </listitem> <listitem> - <para>Know how to configure and install a new - <link linkend="kernelconfig">&os; kernel</link>.</para> + <para>Know how to configure and install a new kernel + (<xref linkend="kernelconfig"/>.</para> </listitem> </itemizedlist> </sect1> - <sect1 xml:id="geom-intro"> - <title>GEOM Introduction</title> - - <para>GEOM permits access and control to classes, such as Master - Boot Records and <acronym>BSD</acronym> labels, through the use - of providers, or the special files in <filename>/dev</filename>. - By supporting various software <acronym>RAID</acronym> - configurations, GEOM transparently provides access to the - operating system and operating system utilities.</para> - </sect1> - <sect1 xml:id="geom-striping"> <info> <title>RAID0 - Striping</title> @@ -119,30 +111,29 @@ </info> <indexterm> - <primary>GEOM</primary> + <primary><acronym>GEOM</acronym></primary> </indexterm> <indexterm> <primary>Striping</primary> </indexterm> - <para>Striping combine several disk drives into a single volume. - In many cases, this is done through the use of hardware - controllers. The GEOM disk subsystem provides software support - for <acronym>RAID</acronym>0, also known as disk - striping.</para> - - <para>In a <acronym>RAID</acronym>0 system, data is split into - blocks that get written across all the drives in the array. - Instead of having to wait on the system to write 256k to one - disk, a <acronym>RAID</acronym>0 system can simultaneously write - 64k to each of four different disks, offering superior I/O + <para>Striping combines several disk drives into a single volume. + Striping can be performed through the use of hardware + <acronym>RAID</acronym> controllers. The + <acronym>GEOM</acronym> disk subsystem provides software support + for disk striping, also known as <acronym>RAID0</acronym>, + without the need for a <acronym>RAID</acronym> disk + controller.</para> + + <para>In <acronym>RAID0</acronym>, data is split into + blocks that are written across all the drives in the array. As + seen in the following illustration, + instead of having to wait on the system to write 256k to one + disk, <acronym>RAID0</acronym> can simultaneously write + 64k to each of the four disks in the array, offering superior <acronym>I/O</acronym> performance. This performance can be enhanced further by using multiple disk controllers.</para> - - <para>Each disk in a <acronym>RAID</acronym>0 stripe must be of - the same size, since I/O requests are interleaved to read or - write to multiple disks in parallel.</para> - + <mediaobject> <imageobject> <imagedata fileref="geom/striping" align="center"/> @@ -153,8 +144,26 @@ </textobject> </mediaobject> + <para>Each disk in a <acronym>RAID0</acronym> stripe must be of + the same size, since <acronym>I/O</acronym> requests are interleaved to read or + write to multiple disks in parallel.</para> + + <note> + <para><acronym>RAID0</acronym> does <emphasis>not</emphasis> + provide any redundancy. This means that if one disk in the + array fails, all of the data on the disks is lost. If the + data is important, implement a backup strategy that regularly + saves backups to a remote system or device.</para> + </note> + + <para>The process for creating a software, + <acronym>GEOM</acronym>-based <acronym>RAID0</acronym> on a &os; + system using commodity disks is as follows. Once the stripe is + created, refer to &man.gstripe..8; for more information on how + to control an existing stripe.</para> + <procedure> - <title>Creating a Stripe of Unformatted ATA Disks</title> + <title>Creating a Stripe of Unformatted <acronym>ATA</acronym> Disks</title> <step> <para>Load the <filename>geom_stripe.ko</filename> @@ -167,9 +176,7 @@ <para>Ensure that a suitable mount point exists. If this volume will become a root partition, then temporarily use another mount point such as - <filename>/mnt</filename>:</para> - - <screen>&prompt.root; <userinput>mkdir /mnt</userinput></screen> + <filename>/mnt</filename>.</para> </step> <step> @@ -199,8 +206,8 @@ Done.</screen> <filename>/dev/stripe</filename> in addition to <filename>st0</filename>. Those include <filename>st0a</filename> and - <filename>st0c</filename>. At this point, a file system - may be created on <filename>st0a</filename> using + <filename>st0c</filename>. At this point, a <acronym>UFS</acronym> file system + can be created on <filename>st0a</filename> using <command>newfs</command>:</para> <screen>&prompt.root; <userinput>newfs -U /dev/stripe/st0a</userinput></screen> @@ -209,12 +216,14 @@ Done.</screen> few seconds, the process will be complete. The volume has been created and is ready to be mounted.</para> </step> - </procedure> + <step> <para>To manually mount the created disk stripe:</para> <screen>&prompt.root; <userinput>mount /dev/stripe/st0a /mnt</userinput></screen> + </step> + <step> <para>To mount this striped file system automatically during the boot process, place the volume information in <filename>/etc/fstab</filename>. In this example, a permanent @@ -224,19 +233,23 @@ Done.</screen> <screen>&prompt.root; <userinput>mkdir /stripe</userinput> &prompt.root; <userinput>echo "/dev/stripe/st0a /stripe ufs rw 2 2" \</userinput> <userinput>>> /etc/fstab</userinput></screen> + </step> + <step> <para>The <filename>geom_stripe.ko</filename> module must also be automatically loaded during system initialization, by adding a line to <filename>/boot/loader.conf</filename>:</para> <screen>&prompt.root; <userinput>echo 'geom_stripe_load="YES"' >> /boot/loader.conf</userinput></screen> + </step> + </procedure> </sect1> <sect1 xml:id="geom-mirror"> <title>RAID1 - Mirroring</title> <indexterm> - <primary>GEOM</primary> + <primary><acronym>GEOM</acronym></primary> </indexterm> <indexterm> <primary>Disk Mirroring</primary> @@ -856,7 +869,7 @@ mountroot></screen> </info> <indexterm> - <primary>GEOM</primary> + <primary><acronym>GEOM</acronym></primary> </indexterm> <indexterm> <primary>Software RAID Devices</primary> @@ -1193,7 +1206,7 @@ raid/r0 OPTIMAL ada0 (ACTIVE (ACTIVE)) </info> <indexterm> - <primary>GEOM</primary> + <primary><acronym>GEOM</acronym></primary> </indexterm> <indexterm> <primary>RAID3</primary> @@ -1325,9 +1338,9 @@ Done.</screen> </sect1> <sect1 xml:id="geom-ggate"> - <title>GEOM Gate Network Devices</title> + <title><acronym>GEOM</acronym> Gate Network Devices</title> - <para>GEOM supports the remote use of devices, such as disks, + <para><acronym>GEOM</acronym> supports the remote use of devices, such as disks, CD-ROMs, and files through the use of the gate utilities. This is similar to <acronym>NFS</acronym>.</para> @@ -1373,7 +1386,7 @@ ggate0 <title>Labeling Disk Devices</title> <indexterm> - <primary>GEOM</primary> + <primary><acronym>GEOM</acronym></primary> </indexterm> <indexterm> <primary>Disk Labels</primary> @@ -1579,10 +1592,10 @@ ufsid/486b6fc16926168e N/A ad4s1f</ </sect1> <sect1 xml:id="geom-gjournal"> - <title>UFS Journaling Through GEOM</title> + <title>UFS Journaling Through <acronym>GEOM</acronym></title> <indexterm> - <primary>GEOM</primary> + <primary><acronym>GEOM</acronym></primary> </indexterm> <indexterm> <primary>Journaling</primary>
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