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<div id="header"><h1 title="MidnightBSD Home"><a href="../" title="MidnightBSD Home">MidnightBSD: The BSD For Everyone</a></h1></div> |
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<h2><img src="../images/oxygen/doc32.png" alt="" /> ZFS Documentation</h2> |
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<h3>Contents</h3> |
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<ul> |
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<li><a href="#s1b">Introduction</a></li> |
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<li><a href="#s1c">Preparing</a></li> |
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<li><a href="#s1d">Examples</a></li> |
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<li><a href="#s1e">Recovery</a></li> |
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<li><a href="#s1f">Snapshots</a></li> |
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<li><a href="#s1g">Send/Receive</a></li> |
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<li><a href="index.html"><strong>Documentation</strong></a></li> |
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<h3 id="s1a">ZFS</h3> |
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<h4 id="s1b">Introduction</h4> |
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<p>ZFS is a file system developed for Oracle Solaris. It was released as open source under the CDDL |
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with OpenSolaris. FreeBSD created a port of the file system for FreeBSD 7.0-CURRENT. It was imported |
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into MidnightBSD with 0.3-CURRENT.</p> |
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|
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<p>ZFS is considered an alternative file system to UFS2 in MidnightBSD. It has independant RAID features |
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that are not tied to GEOM classes. It does not make use of the VFS cache and has some issues with |
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NFS. Advantages include support for very large file systems and large pools of disks. it supports |
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checksum data integrety checking and can repair bad data when raidz is used.</p> |
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|
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<p>MidnightBSD includes ZFS file system and storage pool version 6. You may access pools created |
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on other operating systems at or below this version. If you upgrade to version 6, you will no |
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longer be able to read them on older versions.</p> |
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|
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<h4 id="s1c">Prepairing</h4> |
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<p>ZFS can be used in two ways. You may either dedicate entire disks to ZFS (recommended) or use |
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GPT partitions (mnbsd-zfs in 0.4-CURRENT) to add to a pool. ZFS shines when used with RAID features. |
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</p> |
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|
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<p>If you're going to use RAID, determine how many disks you want to use. It's best to group them |
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in identical sizes. If possible, use the same brand and model of drives when using mirroring. |
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If you have two drives, use mirror. If you have more than two drives, consider using raidz. You |
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may add multiple mirror sets (2 at a time) to the pool.</p> |
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|
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<p>ZFS also supports adding spare drives to the pool. They will be used automatically when a drive fails.</p> |
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<p>It is strongly recommended to use ZFS only with amd64 MidnightBSD and only on systems with more |
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than 1GB of RAM. It will require tuning sysctl's to get the right balance of memory usage. Particularly, |
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you need to watch the ARC size as it can grow very large</p> |
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|
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<p>MidnightBSD does not support booting from ZFS at this time. It may be added in a future release. You need |
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a UFS/UFS2 partition for / including /boot, but /var, /tmp, /usr and /home can be on ZFS.</p> |
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|
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<h4 id="s1d">Examples</h4> |
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<p>In these examples, mpool and tank are used as pool names. You can pick any name for the pool, but tank is very |
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common. After creating a pool named tank, you'll see /tank</p> |
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|
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<p>You will most likely want to add zfs_enable="YES" into /etc/rc.conf so that ZFS is loaded on system startup</p> |
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<p>Create a mirror</p> |
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<code>zpool create mpool mirror /dev/ad0 /dev/ad1</code> |
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|
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<p>Add a spare drive</p> |
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<code> zpool add mpool spare /dev/ad3</code> |
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|
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<p>Check status</p> |
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<code>zpool status</code> |
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|
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<p>Listing information about pools</p> |
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<code>zpool list</code> |
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<code>zfs list</code> |
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|
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<p>Create file systems</p> |
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<code>zfs create mpool/data</code> |
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|
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<p>Use raidz instead (raid 5 like mode)</p> |
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<code>zpool add tank raidz /dev/ad0 /dev/ad1 /dev/ad2</code> |
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|
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<p>Scrub data (check for errors)</p> |
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<code>zpool scrub tank</code> |
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|
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<h4 id="s1e">Recovery</h4> |
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<p>During a hardware upgrade such as moving to a new motherboard or controller, |
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one might find their zpool damaged. Usually the cause is that the device name has |
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changed. For instance, a recent upgrade moved ad6 to ad12.</p> |
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<p>To fix this problem, |
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several steps are required. |
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<ul><li><code>rm /boot/zfs/zpool.cache & shutdown -r now</code></li> |
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<li> |
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<code>zpool list</code>. This should not show the pool. |
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</li> |
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<li><code>zpool import</code>. It should show you possible pools to recover.</li> |
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<li> |
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Finally, try <code>zpool import <em>name of pool</em></code>. |
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</li> |
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</ul> |
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|
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<p>To verify it worked, run <code>zpool list</code></p> |
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<h4 id="s1f">Snapshots</h4> |
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<p>A ZFS snapshot, is a point in time copy or bookmark of your data. You can use |
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it to compare changes made to a file system or to backup a file system. This allows |
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you to get your data back after trying an upgrade, etc. It can be a handy trick |
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to make copies of jails easily. |
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</p> |
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<p>You can create a snapshot named 1 using the following:</p> |
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<code>zfs snapshot tank/test@1</code> |
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<p>You can also apply a snapshot recursively to all file systems in a pool |
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with the r flag</p> |
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<code>zfs snapshot -r tank/home@now</code> |
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<p>As more changes occur to a file system, the amount of disk space a snapshot |
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takes increases. You will want to purge old snapshots to free up disk space |
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when they are no longer needed.</p> |
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<code>zfs destroy tank/home@now</code> |
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<p>You can use the rename command to rename a snapshot, the hold command to |
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prevent removal of a snapshot, and many more options. Consult the |
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relevant man pages for more information.</p> |
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<p>Finally, you can list snapshots</p> |
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<code>zfs list -t snapshot</code> |
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<p>You can also make zfs list show snapshots by default by changing this setting |
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<code>zpool set listsnapshots=on tank</code></p> |
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<h4 id="s1g">Using Send and Receive</h4> |
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<p>You can use zfs to send a snapshot to the same or another pool with the |
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zfs send and receive commands. This can be used to backup ZFS file systems |
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to another location such as an external disk.</p> |
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|
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<p>To backup the snapshot named 1 from file system test: |
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<code> |
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zfs send tank/test@1 | zfs receive tank/testback |
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</code> |
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</p> |
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|
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<h4 id="s1h">Advanced format hard drives (4k sector)</h4> |
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|
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<p>Many 4k sector drives do not report their size properly in a bad attempt |
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at backward compatibility. ZFS works fine with drives that report |
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properly, but for the rest of them the following workaround is |
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recommended. |
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</p> |
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<p> |
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<code> |
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gpart create -s gpt ada0 |
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|
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# create partitions |
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gpart add -a 1m -t mnbsd-zfs -l drive0 ada0 |
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gpart add -a 1m -t mnbsd-zfs -l drive1 ada1 |
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|
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# use gnop to make 4k friendly devices |
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gnop create -S 4k gpt/drive0 |
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gnop create -S 4k gpt/drive1 |
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|
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# make a mirror |
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zpool create mpool mirror /dev/gpt/drive0.nop /dev/gpt/drive1.nop |
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# export pool and remove virtual devices |
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zpool export mpool |
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gnop destroy gpt/drive0.nop |
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gnop destroy gpt/drive1.nop |
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# import and keep labels (via -d flag) |
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zpool import -d /dev/gpt mpool |
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</code> |
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