Date: Fri, 25 Apr 2014 16:10:58 +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: r44664 - head/en_US.ISO8859-1/books/handbook/geom Message-ID: <201404251610.s3PGAwMV012721@svn.freebsd.org>
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Author: dru Date: Fri Apr 25 16:10:58 2014 New Revision: 44664 URL: http://svnweb.freebsd.org/changeset/doc/44664 Log: Editorial review of RAID3 chapter. 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 25 15:26:06 2014 (r44663) +++ head/en_US.ISO8859-1/books/handbook/geom/chapter.xml Fri Apr 25 16:10:58 2014 (r44664) @@ -895,8 +895,8 @@ mountroot></screen> In a <acronym>RAID</acronym>3 system, data is split up into a number of bytes that are written across all the drives in the array except for one disk which acts as a dedicated parity disk. - This means that reading 1024KB from a - <acronym>RAID</acronym>3 implementation will access all disks in + This means that disk reads from a + <acronym>RAID</acronym>3 implementation access all disks in the array. Performance can be enhanced by using multiple disk controllers. The <acronym>RAID</acronym>3 array provides a fault tolerance of 1 drive, while providing a capacity of 1 - @@ -907,10 +907,19 @@ mountroot></screen> <para>At least 3 physical hard drives are required to build a <acronym>RAID</acronym>3 array. Each disk must be of the same - size, since I/O requests are interleaved to read or write to + size, since <acronym>I/O</acronym> requests are interleaved to read or write to multiple disks in parallel. Also, due to the nature of <acronym>RAID</acronym>3, the number of drives must be equal to 3, 5, 9, 17, and so on, or 2^n + 1.</para> + + <para>This section demonstrates how to create a software + <acronym>RAID</acronym>3 on a &os; system.</para> + + <note> + <para>While it is theoretically possible to boot from a + <acronym>RAID</acronym>3 array on &os;, that configuration + is uncommon and is not advised.</para> + </note> <sect2> <title>Creating a Dedicated <acronym>RAID</acronym>3 @@ -922,30 +931,24 @@ mountroot></screen> <acronym>RAID</acronym>3 array on &os; requires the following steps.</para> - <note> - <para>While it is theoretically possible to boot from a - <acronym>RAID</acronym>3 array on &os;, that configuration - is uncommon and is not advised.</para> - </note> - <procedure> <step> <para>First, load the <filename>geom_raid3.ko</filename> - kernel module by issuing the following command:</para> + kernel module by issuing one of the following commands:</para> <screen>&prompt.root; <userinput>graid3 load</userinput></screen> - <para>Alternatively, it is possible to manually load the - <filename>geom_raid3.ko</filename> module:</para> + <para>or:</para> - <screen>&prompt.root; <userinput>kldload geom_raid3.ko</userinput></screen> + <screen>&prompt.root; <userinput>kldload geom_raid3</userinput></screen> </step> <step> - <para>Create or ensure that a suitable mount point - exists:</para> + <para>Ensure that a suitable mount point + exists. This command creates a new directory to use as + the mount point:</para> - <screen>&prompt.root; <userinput>mkdir <replaceable>/multimedia/</replaceable></userinput></screen> + <screen>&prompt.root; <userinput>mkdir <replaceable>/multimedia</replaceable></userinput></screen> </step> <step> @@ -971,7 +974,7 @@ Done.</screen> <step> <para>Partition the newly created - <filename>gr0</filename> device and put a UFS file + <filename>gr0</filename> device and put a <acronym>UFS</acronym> file system on it:</para> <screen>&prompt.root; <userinput>gpart create -s GPT /dev/raid3/gr0</userinput> @@ -989,7 +992,7 @@ Done.</screen> </step> </procedure> - <para>Additional configuration is needed to retain the above + <para>Additional configuration is needed to retain this setup across system reboots.</para> <procedure>
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