Date: Tue, 29 Oct 2013 05:25:32 +0000 (UTC) From: Warren Block <wblock@FreeBSD.org> To: doc-committers@freebsd.org, svn-doc-projects@freebsd.org Subject: svn commit: r43070 - projects/zfsupdate-201307/en_US.ISO8859-1/books/handbook/zfs Message-ID: <201310290525.r9T5PWHH007869@svn.freebsd.org>
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Author: wblock Date: Tue Oct 29 05:25:31 2013 New Revision: 43070 URL: http://svnweb.freebsd.org/changeset/doc/43070 Log: Apply the latest patch from Allan Jude. Submitted by: Allan Jude <freebsd@allanjude.com> Modified: projects/zfsupdate-201307/en_US.ISO8859-1/books/handbook/zfs/chapter.xml Modified: projects/zfsupdate-201307/en_US.ISO8859-1/books/handbook/zfs/chapter.xml ============================================================================== --- projects/zfsupdate-201307/en_US.ISO8859-1/books/handbook/zfs/chapter.xml Tue Oct 29 02:03:09 2013 (r43069) +++ projects/zfsupdate-201307/en_US.ISO8859-1/books/handbook/zfs/chapter.xml Tue Oct 29 05:25:31 2013 (r43070) @@ -12,6 +12,16 @@ <surname>Rhodes</surname> <contrib>Written by </contrib> </author> + <author> + <firstname>Allan</firstname> + <surname>Jude</surname> + <contrib>Written by </contrib> + </author> + <author> + <firstname>Benedict</firstname> + <surname>Reuschling</surname> + <contrib>Written by </contrib> + </author> </authorgroup> </chapterinfo> @@ -470,12 +480,52 @@ errors: No known data errors</screen> <sect2 id="zfs-zpool-create"> <title>Creating & Destroying Storage Pools</title> + <para>Creating a ZFS Storage Pool (<acronym>zpool</acronym>) + involves making a number of decisions that are relatively + permanent because the structure of the pool cannot be + changed after the pool has been created. The most important + decision is what type(s) of vdevs to group the physical disks + into. See the list of <link + linkend="zfs-term-vdev">vdev types</link> for details about + the possible options. Once the pool has been created, most + vdev types do not allow additional disks to be added to the + vdev. The exceptions are mirrors, which allow additional + disks to be added to the vdev, and stripes, which can be + upgraded to mirrors by attaching an additional to the vdev. + Although additional vdevs can be added to a pool, the layout + of the pool cannot be changed once the pool has been created, + instead the data must be backed up and the pool + recreated.</para> + <para></para> </sect2> <sect2 id="zfs-zpool-attach"> <title>Adding & Removing Devices</title> + <para>Adding additional disks to a zpool can be broken down into + two separate cases, attaching an additional disk to an + existing vdev with the <literal>zpool attach</literal> + command, or adding additional vdevs to the pool with the + <literal>zpool add</literal> command. Only some + <link linkend="zfs-term-vdev">vdev types</link> allow disks to + be added to the vdev after the fact.</para> + + <para>When adding additional disks to the existing vdev is not + an option, such as in the case of RAID-Z, the other option is + to add an additional vdev to the pool. It is possible, but + discouraged, to mix vdev types. ZFS stripes data across each + of the vdevs, for example if there are two mirror vdevs, then + this is effectively a RAID 10, striping the writes across the + two sets of mirrors. Because of the way that space is + allocated in ZFS in order to attempt to have each vdev reach + 100% full at the same time, there is a performance penalty if + the vdevs have different amounts of free space.</para> + + <para>Currently, vdevs cannot be removed from a zpool, and disks + can only be removed from a mirror if there is enough remaining + redundancy.</para> + <para>Creating a ZFS Storage Pool (<acronym>zpool</acronym>) involves making a number of decisions that are relatively permanent. Although additional vdevs can be added to a pool, @@ -485,22 +535,84 @@ errors: No known data errors</screen> zpool.</para> </sect2> + <sect2 id="zfs-zpool-replace"> + <title>Replacing a Working Devices</title> + + <para>There are a number of situations in which it may be + desirable to replacing a disk with a different disk. This + process requires connecting the new disk at the same time as + the disk to be replaced. The + <literal>zpool replace</literal> command will copy all of the + data from the old disk to the new one. Once this operation + completes, the old disk is disconnected from the vdev. If the + newer disk is larger this may allow your zpool to grow, see + the <link linkend="zfs-zpool-online">Growing a Pool</link> + section.</para> + </sect2> + <sect2 id="zfs-zpool-resilver"> <title>Dealing with Failed Devices</title> - <para></para> + <para>When a disk fails and the physical device is replaced, ZFS + needs to be told to begin the <link + linkend="zfs-term-resilver">resilver</link> operation, where + the data that was on the failed device will be recalculated + from the available redundancy and written to the new + device.</para> + </sect2> + + <sect2 id="zfs-zpool-online"> + <title>Growing a Pool</title> + + <para>The usable size of a redundant ZFS pool is limited by the + size of the smallest device in the vdev. If you sequentially + replace each device in the vdev then when the smallest device + has completed the replace or resilver operation, the pool + can then grow based on the size of the new smallest device. + This expansion can be triggered with the + <literal>zpool online</literal> command with the -e flag on + each device. Once the expansion of each device is complete, + the additional space will be available in the pool.</para> </sect2> <sect2 id="zfs-zpool-import"> <title>Importing & Exporting Pools</title> - <para></para> + <para>Pools can be exported in preperation for moving them to + another system. All datasets are unmounted, and each device + is marked as exported but still locked so it cannot be used + by other disk subsystems. This allows pools to be imported on + other machines, other operating systems that support ZFS, and + even different hardware architectures (with some caveats, see + the zpool man page). The -f flag can be used to force + exporting a pool, in cases such as when a dataset has open + files. If you force an export, the datasets will be forcibly + unmounted such can have unexpected side effects.</para> + + <para>Importing a pool will automatically mount the datasets, + which may not be the desired behavior. The -N command line + param will skip mounting. The command line parameter -o sets + temporary properties for this import only. The altroot= + property allows you to import a zpool with a base of some + mount point, instead of the root of the file system. If the + pool was last used on a different system and was not properly + exported, you may have to force an import with the -f flag. + The -a flag will import all pools that do not appear to be + in use by another system.</para> </sect2> <sect2 id="zfs-zpool-upgrade"> <title>Upgrading a Storage Pool</title> - <para></para> + <para>After FreeBSD has been upgraded, or if a pool has been + imported from a system using an older verison of ZFS, the pool + must be manually upgraded to the latest version of ZFS. This + process is unreversable, so consider if the pool may ever need + to be imported on an older system before upgrading. Onle once + the <literal>zpool upgrade</literal> command has completed + will the newer features of ZFS be available. An upgrade + cannot be undone. The -v flag can be used to see what new + features will be supported by upgrading.</para> </sect2> <sect2 id="zfs-zpool-status"> @@ -556,7 +668,7 @@ data 288G 1.53T ada1 - - 0 4 5.61K 61.7K ada2 - - 1 4 5.04K 61.7K ----------------------- ----- ----- ----- ----- ----- -----</screen> -</sect2> + </sect2> <sect2 id="zfs-zpool-split"> <title>Splitting a Storage Pool</title> @@ -1389,7 +1501,8 @@ vfs.zfs.vdev.cache.size="5M"</programlis <entry id="zfs-term-snapshot">Snapshot</entry> <entry>The <link - linkend="zfs-term-cow">copy-on-write</link> (<acronym>COW</acronym>) design of + linkend="zfs-term-cow">copy-on-write</link> + (<acronym>COW</acronym>) design of <acronym>ZFS</acronym> allows for nearly instantaneous consistent snapshots with arbitrary names. After taking a snapshot of a dataset (or a recursive snapshot of a
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