Difference between revisions of "ZFS"
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It should not have to be stated, but be careful with this command! | It should not have to be stated, but be careful with this command! | ||
− | Once you have the list of drives, it is now time to get the id's of the drives you will be using. The [http://zfsonlinux.org/faq.html#WhatDevNamesShouldIUseWhenCreatingMyPool zfs on | + | Once you have the list of drives, it is now time to get the id's of the drives you will be using. The [http://zfsonlinux.org/faq.html#WhatDevNamesShouldIUseWhenCreatingMyPool zfs on Linux developers recommend] using device ids when creating ZFS storage pools of less than 10 devices. To find the id's for your device, simply: |
$ ls -lah /dev/disk/by-id/ | $ ls -lah /dev/disk/by-id/ | ||
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lrwxrwxrwx 1 root root 9 Aug 12 16:26 ata-ST3000DM001-9YN166_S1F0KDGY -> ../../sdb | lrwxrwxrwx 1 root root 9 Aug 12 16:26 ata-ST3000DM001-9YN166_S1F0KDGY -> ../../sdb | ||
− | Now finally, create the ZFS pool: | + | Now, finally, create the ZFS pool: |
# zpool create -f -m <mount> <pool> raidz <ids> | # zpool create -f -m <mount> <pool> raidz <ids> |
Revision as of 22:51, 29 March 2013
Template:Article summary start Template:Article summary text Template:Article summary heading Template:Article summary wiki Template:Article summary wiki Template:Article summary end
ZFS is an advanced filesystem created by Sun Microsystems (now owned by Oracle) and released for OpenSolaris in November 2005. Features of ZFS include: pooled storage (integrated volume management -- zpool), Copy-on-write, snapshots, data integrity verification and automatic repair (scrubbing), RAID-Z, and a maximum 16 Exabyte volume size. ZFS is licensed under the Common Development and Distribution License (CDDL).
Described as "The last word in filesystems" ZFS is stable, fast, secure, and future-proof. Being licensed under the GPL incompatible CDDL, it is not possible for ZFS to be distributed along with the Linux Kernel. This requirement, however, does not prevent a native Linux kernel module from being developed and distributed by a third party, as is the case with zfsonlinux.org (ZOL).
Contents
Installation
The ZFS kernel module is available in the AUR via zfsAUR.
Unofficial repository
For fast and effortless installation and updates, the "archzfs" signed repository is available to add to your pacman.conf
:
/etc/pacman.conf
[archzfs] Server = http://demizerone.com/$repo/core/$arch
The repository and packages are signed with the maintainer's PGP key which is verifiable here: http://demizerone.com. This key is not trusted by any of the Arch Linux master keys, so it will need to be locally signed before use. See pacman-key.
Add the maintainer's key,
# pacman-key -r 0EE7A126
and locally sign to add it to the system's trust database,
# pacman-key --lsign-key 0EE7A126
Once the key has been signed, it is now possible to update the package database,
# pacman -Syy
and install ZFS packages:
# pacman -S archzfs
Archzfs testing repository
If you have the testing repository active in pacman.conf
then it is possible to use the archzfs repository that tracks the testing kernel.
# /etc/pacman.conf
[archzfs] Server = http://demizerone.com/$repo/testing/$arch
Archiso tracking repository
ZFS can easily be used from within the archiso live environment by using the special archiso tracking repository for ZFS. This repository makes it easy to install Arch Linux on a root ZFS filesystem, or to mount ZFS pools from within an archiso live environment using an up-to-date live medium. To use this repository from the live environment, add the following server line to pacman.conf:
/etc/pacman.conf
[archzfs] Server = http://demizerone.com/$repo/archiso/$arch
This repository and packages are also signed, so the key must be locally signed following the steps listed in the previous section before use. For a guide on how to install Arch Linux on to a root ZFS filesystem, see Installing Arch Linux on ZFS.
Configuration
ZFS is considered a "zero administration" filesystem by its creators, therefore configuring ZFS is very straight forward. Configuration is done primarily with two commands, zfs
and zpool
.
mkinitramfs hook
If you are using ZFS on your root filesystem, then you will need to add the ZFS hook to mkinitcpio.conf. If you are not using ZFS for your root filesystem, then you do not need to add the ZFS hook.
You will need to change your kernel parameters to include the dataset you want to boot. You can use zfs=bootfs
to use the ZFS bootfs (set via zpool set bootfs=rpool/ROOT/arch rpool
) or you can set the kernel parameters to zfs=<pool>/<dataset>
to boot directly from a ZFS dataset.
To see all available options for the ZFS hook:
$ mkinitcpio -H zfs
To use the mkinitcpio hook, you will need to add zfs
to your HOOKS
in /etc/mkinitcpio.conf
:
/etc/mkinitcpio.conf
... HOOKS="base udev autodetect modconf encrypt zfs filesystems usbinput" ...
It is important to place this after any hooks which are needed to prepare the drive before it is mounted. For example, if your ZFS volume is encrypted, then you will need to place encrypt before the zfs hook to unlock it first.
Recreate the ramdisk:
# mkinitcpio -p linux
Automatic Start
For ZFS to live by its "zero administration" namesake, the zfs daemon must be loaded at startup. A benefit to this is that it is not necessary to mount your zpool in /etc/fstab
; the zfs daemon imports and mounts one zfs pool automatically. The daemon mounts a zfs pool reading the file /etc/zfs/zpool.cache
, so the zfs pool that you want to automatically mounted must write the file there.
Set a pool as to be automatically mounted by the zfs daemon:
# zpool set cachefile=/etc/zfs/zpool.cache <pool>
Systemd
Enable the service so it is automatically started at boot time:
# systemctl enable zfs.service
To manually start the daemon:
# systemctl start zfs.service
Create a storage pool
Use # parted --list
to see a list of all available drives. It is not necessary to partition your drives before creating the zfs filesystem, this will be done automatically. However, if you feel the need to completely wipe your drive before creating the filesystem, this can be easily done with the dd command.
# dd if=/dev/zero of=/dev/<device>
It should not have to be stated, but be careful with this command!
Once you have the list of drives, it is now time to get the id's of the drives you will be using. The zfs on Linux developers recommend using device ids when creating ZFS storage pools of less than 10 devices. To find the id's for your device, simply:
$ ls -lah /dev/disk/by-id/
The ids should look similar to the following:
lrwxrwxrwx 1 root root 9 Aug 12 16:26 ata-ST3000DM001-9YN166_S1F0JKRR -> ../../sdc lrwxrwxrwx 1 root root 9 Aug 12 16:26 ata-ST3000DM001-9YN166_S1F0JTM1 -> ../../sde lrwxrwxrwx 1 root root 9 Aug 12 16:26 ata-ST3000DM001-9YN166_S1F0KBP8 -> ../../sdd lrwxrwxrwx 1 root root 9 Aug 12 16:26 ata-ST3000DM001-9YN166_S1F0KDGY -> ../../sdb
Now, finally, create the ZFS pool:
# zpool create -f -m <mount> <pool> raidz <ids>
- create: subcommand to create the pool.
- -f: Force creating the pool. This is to overcome the "EFI label error". See #does not contain an EFI label.
- -m: The mount point of the pool. If this is not specified, than your pool will be mounted to
/<pool>
.
- pool: This is the name of the pool. Change it to whatever you like.
- raidz: This is the type of virtual device that will be created from the pool of devices. Raidz is a special implementation of raid5. See Jeff Bonwick's Blog -- RAID-Z for more information about raidz.
- ids: The names of the drives or partitions that you want to include into your pool. Get it from
/dev/disk/by-id
.
Here is an example for the full command:
# zpool create -f -m /mnt/data bigdata raidz ata-ST3000DM001-9YN166_S1F0KDGY ata-ST3000DM001-9YN166_S1F0JKRR ata-ST3000DM001-9YN166_S1F0KBP8 ata-ST3000DM001-9YN166_S1F0JTM1
If the command is successful, there will be no output. Using the $ mount
command will show that you pool is mounted. Using # zpool status
will show that your pool has been created.
# zpool status
pool: bigdata state: ONLINE scan: none requested config: NAME STATE READ WRITE CKSUM bigdata ONLINE 0 0 0 -0 ONLINE 0 0 0 ata-ST3000DM001-9YN166_S1F0KDGY-part1 ONLINE 0 0 0 ata-ST3000DM001-9YN166_S1F0JKRR-part1 ONLINE 0 0 0 ata-ST3000DM001-9YN166_S1F0KBP8-part1 ONLINE 0 0 0 ata-ST3000DM001-9YN166_S1F0JTM1-part1 ONLINE 0 0 0 errors: No known data errors
At this point it would be good to reboot your computer to make sure your ZFS pool is mounted at boot. It is best to deal with all errors before transferring your data.
Usage
To see all the commands available in ZFS, use
$ man zfs
or
$ man zpool
Scrub
ZFS pools should be scrubbed at least once a week. To scrub your pool
# zpool scrub <pool>
To do automatic scrubbing once a week, set the following line in your root crontab
# crontab -e
... 30 19 * * 5 zpool scrub <pool> ...
Replace <pool>
with the name of your ZFS storage pool.
Check zfs pool status
To print a nice table with statistics about your ZFS pool, including and read/write errors, use
# zpool status -v
Destroy a storage pool
ZFS makes it easy to destroy a mounted storage pool, removing all metadata about the ZFS device. This command destroys any data contained in the pool.
# zpool destroy <pool>
and now when checking the status
# zpool status
no pools available
To find the name of your pool, see #Check zfs pool status.
Export a storage pool
If you are going to use the pool in a different system, or are doing
Swap partition
zfs does not allows to use swapfiles, but you can use a zfs volume as swap partition. It is importart to set the ZVOL block size to match the system page size, for x86_64 systems that is 4k
Create a 8gb zfs volume
# zfs create -V 8gb -b 4K <pool>/swap
Prepare it as swap partition
# mkswap /dev/zvol/<pool>/maindisk/swap
Enable swap
# swapon /dev/zvol/<pool>/maindisk/swap
To make it permament you need to edit your /etc/fstab
Add a line to /etc/fstab
/dev/zvol/<pool>/swap none swap defaults 0 0
Troubleshooting
does not contain an EFI label
The following error will occur when attempting to create a zfs filesystem,
/dev/disk/by-id/<id> does not contain an EFI label but it may contain partition
The way to overcome this is to use -f
with the zfs create command.
No hostid found
An error that occurs at boot with the following lines appearing before initscript output:
ZFS: No hostid found on kernel command line or /etc/hostid.
This warning occurs because the ZFS module does not have access to the spl hosted. There are two solutions, for this. You can either place your spl hostid in the kernel parameters in your boot loader. For example, adding spl.spl_hostid=0x00bab10c
.
The other solution is to make sure that there is a hostid in /etc/hostid
, and then regenerate the initramfs image. Which will copy the hostid into the initramfs image.
# mkinitcpio -p linux
On boot the zfs pool does not mount stating: "pool may be in use from other system"
You can always ignore the check adding zfs_force=1
in your kernel parameters, but it is not advisable as a permanent solution.
First of all double check you actually exported the pool correctly. Exporting the zpool clears the hostid marking the ownership. So during the first boot the zpool should mount correctly. If it does not there is some other problem.
Reboot again, if the zfs pool refuses to mount it means your hostid is not yet correctly set in the early boot phase and it confuses zfs. So you have to manually tell zfs the correct number, once the hostid is coherent across the reboots the zpool will mount correctly.
Boot using zfs_force and write down your hostid. This one is just an example.
% hostid 0a0af0f8
Follow the previous section to set it.
Tips and tricks
Emergency chroot repair with archzfs
Here is how to use the archiso to get into your ZFS filesystem for maintenance.
Boot the latest archiso and bring up your network
# wifi-menu # ip link set eth0 up
Test the network connection
# ping google.com
Sync the pacman package database
# pacman -Syy
(optional) Install your favorite text editor
# pacman -S vim
Add archzfs archiso repository to pacman.conf
/etc/pacman.conf
[archzfs] Server = http://demizerone.com/$repo/archiso/$arch
Sync the pacman package database
# pacman -Syy
Install the ZFS package group
# pacman -S archzfs
Load the ZFS kernel modules
# modprobe zfs
Import your pool
# zpool import -a -R /mnt
Mount your boot partitions (if you have them)
# mount /dev/sda2 /mnt/boot # mount /dev/sda1 /mnt/boot/efi
Chroot into your zfs filesystem
# arch-chroot /mnt /bin/bash
Check your kernel version
# pacman -Qi linux # uname -r
uname will show the kernel version of the archiso. If they are different, you will need to run depmod (in the chroot) with the correct kernel version of your chroot installation:
# depmod -a 3.6.9-1-ARCH (version gathered from pacman -Qi linux)
This will load the correct kernel modules for the kernel version installed in your chroot installation.
Regenerate your ramdisk
# mkinitcpio -p linux
There should be no errors.