svn commit: r44770 - head/en_US.ISO8859-1/books/handbook/config

Gavin Atkinson gavin at FreeBSD.org
Sat May 17 19:52:19 UTC 2014


On Tue, 6 May 2014, Dru Lavigne wrote:
> Author: dru
> Date: Tue May  6 14:18:28 2014
> New Revision: 44770
> URL: http://svnweb.freebsd.org/changeset/doc/44770
> 
> Log:
>   Editorial review of Swap Space section.
>   This really belongs in the Storage chapter and should have a reference for ZFS swap.

We generally recommend against using swap on ZFS, as it can currently be 
unstable under low-memory or high-activity situations.  This will likely 
be fixed in the future though.

Generally, I'll create a separate gmirror partition or similar for swap, 
and use the rest of the disks for the ZFS partiton.

Gavin

>   
>   Sponsored by:	iXsystems
> 
> Modified:
>   head/en_US.ISO8859-1/books/handbook/config/chapter.xml
> 
> Modified: head/en_US.ISO8859-1/books/handbook/config/chapter.xml
> ==============================================================================
> --- head/en_US.ISO8859-1/books/handbook/config/chapter.xml	Tue May  6 13:38:06 2014	(r44769)
> +++ head/en_US.ISO8859-1/books/handbook/config/chapter.xml	Tue May  6 14:18:28 2014	(r44770)
> @@ -2703,9 +2703,9 @@ kern.maxvnodes: 100000</screen>
>    <sect1 xml:id="adding-swap-space">
>      <title>Adding Swap Space</title>
>  
> -    <para>Sometimes a system requires more swap space.  There are
> -      three ways to increase swap space: add a new hard drive,
> -      enable swap over <literal>NFS</literal>, or create a swap file
> +    <para>Sometimes a system requires more swap space.  This section
> +      describes two methods to increase swap space: adding swap to an
> +      existing partition or new hard drive, and creating a swap file
>        on an existing partition.</para>
>  
>      <para>For information on how to encrypt swap space, which options
> @@ -2713,16 +2713,16 @@ kern.maxvnodes: 100000</screen>
>        <xref linkend="swap-encrypting"/>.</para>
>  
>      <sect2 xml:id="new-drive-swap">
> -      <title>Swap on a New or Existing Hard Drive</title>
> +      <title>Swap on a New Hard Drive or Existing Partition</title>
>  
>        <para>Adding a new hard drive for swap gives better performance
> -	than adding a partition on an existing drive.  Setting up
> +	than using a partition on an existing drive.  Setting up
>  	partitions and hard drives is explained in
>  	<xref linkend="disks-adding"/> while
>  	<xref linkend="configtuning-initial"/> discusses partition
>  	layouts and swap partition size considerations.</para>
>  
> -      <para>Use &man.swapon.8; to add a swap partition to the system.
> +      <para>Use <command>swapon</command> to add a swap partition to the system.
>  	For example:</para>
>  
>        <screen>&prompt.root; <userinput>swapon <replaceable>/dev/ada1s1b</replaceable></userinput></screen>
> @@ -2730,10 +2730,10 @@ kern.maxvnodes: 100000</screen>
>        <warning>
>  	<para>It is possible to use any partition not currently
>  	  mounted, even if it already contains data.  Using
> -	  &man.swapon.8; on a partition that contains data will
> +	  <command>swapon</command> on a partition that contains data will
>  	  overwrite and destroy that data.  Make sure that the
>  	  partition to be added as swap is really the intended
> -	  partition before running &man.swapon.8;.</para>
> +	  partition before running <command>swapon</command>.</para>
>        </warning>
>  
>        <para>To automatically add this swap partition on boot, add an
> @@ -2742,34 +2742,26 @@ kern.maxvnodes: 100000</screen>
>        <programlisting><replaceable>/dev/ada1s1b</replaceable>	none	swap	sw	0	0</programlisting>
>  
>        <para>See &man.fstab.5; for an explanation of the entries in
> -	<filename>/etc/fstab</filename>.</para>
> -    </sect2>
> -
> -    <sect2 xml:id="nfs-swap">
> -      <title>Swapping over <literal>NFS</literal></title>
> -
> -      <para>Swapping over <literal>NFS</literal> is only recommended
> -	when there is no local hard disk to swap to.
> -	<literal>NFS</literal> swapping will be limited by the
> -	available network bandwidth and puts an additional burden
> -	on &man.nfsd.8;.</para>
> +	<filename>/etc/fstab</filename>.  More information about
> +	<command>swapon</command> can be found in
> +	&man.swapon.8;.</para>
>      </sect2>
>  
>      <sect2 xml:id="create-swapfile">
> -      <title>Swapfiles</title>
> +      <title>Creating a Swap File</title>
>  
> -      <para>To create a swap file, specify its size.  The following
> +      <para>To instead create a swap file, specify its size.  The following
>  	example creates a 64MB file named
>  	<filename>/usr/swap0</filename>.</para>
>  
>        <example>
> -	<title>Creating a Swapfile on &os;</title>
> +	<title>Creating a Swap File on &os;</title>
>  
>  	<orderedlist>
>  	  <listitem>
>  	    <para>The <filename>GENERIC</filename> kernel already
> -	      includes the memory disk driver (&man.md.4;) required
> -	      for this operation.  When building a custom kernel,
> +	      includes the required memory disk driver.
> +	      When building a custom kernel,
>  	      make sure to include the following line in the custom
>  	      configuration file:</para>
>  
> @@ -2780,31 +2772,33 @@ kern.maxvnodes: 100000</screen>
>  	  </listitem>
>  
>  	  <listitem>
> -	    <para>First, create the swapfile
> +	    <para>Create the swap file,
>  	      <filename>/usr/swap0</filename>:</para>
>  
> -	    <screen>&prompt.root; <userinput>dd if=/dev/zero of=/usr/swap0 bs=1024k count=64</userinput></screen>
> +	    <screen>&prompt.root; <userinput>dd if=/dev/zero of=<replaceable>/usr/swap0</replaceable> bs=1024k count=<replaceable>64</replaceable></userinput></screen>
>  	  </listitem>
>  
>  	  <listitem>
>  	    <para>Then, set proper permissions on
>  	      <filename>/usr/swap0</filename>:</para>
>  
> -	    <screen>&prompt.root; <userinput>chmod 0600 /usr/swap0</userinput></screen>
> +	    <screen>&prompt.root; <userinput>chmod 0600 <replaceable>/usr/swap0</replaceable></userinput></screen>
>  	  </listitem>
>  
>  	  <listitem>
>  	    <para>Enable the swap file in
>  	      <filename>/etc/rc.conf</filename>:</para>
>  
> -	    <programlisting>swapfile="/usr/swap0"   # Set to name of swapfile if aux swapfile desired.</programlisting>
> +	    <programlisting>swapfile="<replaceable>/usr/swap0</replaceable>"   # Set to name of swap file</programlisting>
>  	  </listitem>
>  
>  	  <listitem>
> -	    <para>Reboot the machine or, to enable the swap file
> -	      immediately, type:</para>
> +	    <para>To enable the swap file
> +	      immediately, specify a free memory device.  Refer to
> +	      <xref linkend="disks-virtual"/> for more information
> +	      about memory devices.</para>
>  
> -	    <screen>&prompt.root; <userinput>mdconfig -a -t vnode -f /usr/swap0 -u 0 && swapon /dev/md0</userinput></screen>
> +	    <screen>&prompt.root; <userinput>mdconfig -a -t vnode -f <replaceable>/usr/swap0</replaceable> -u <replaceable>0</replaceable> && swapon /dev/md<replaceable>0</replaceable></userinput></screen>
>  	  </listitem>
>  	</orderedlist>
>        </example>
> 
> 


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