Click here to close now.

Welcome!

Linux Authors: Elizabeth White, Carmen Gonzalez, Esmeralda Swartz, Pat Romanski, Lori MacVittie

Related Topics: Linux, Open Source, Virtualization

Linux: Article

ZFS on Linux

How ZFS on Linux compares to ZFS on Illumos or FreeBSD

On March 27, 2013, ZoL maintainers announced that the 0.6.1 release was ready for wide scale deployment on everything from desktops to servers. Yet, due to lack of maturity and adoption of the ZoL project, maintainers and/or advocates of ZFS aren't comfortable to run ZoL in production yet.

The reason behind the reluctance to use ZoL in production is that ZFS on Solaris took a large number of years to reach maturity and went through ups and downs of bugs related to data corruption and other issues. In the same way, ZoL will need some time to mature as product. It will take about a year to be mature as more people deploy it in production. If developers want to take advantage of ZFS, they can start rolling out less important database servers (i.e. reporting servers, 3rd slave databases) into production and experience the product for about 6 months before rolling out to all database servers. This will give users the confidence and experience to work with ZoL. Alternatively, developers may want to run ZFS on OmniOS because it's been battle tested for decades now.

How ZFS on Linux Compares to ZFS on Illumos or FreeBSD
The implementation of ZFS on Linux when compared to running ZFS on Illumos or FreeBSD is not very different from the perspective of the system administrator. The management and general usage is nearly identical. The only differences are OS specific functionality. For example, on FreeBSD if a user wants to use a zvol for swap space, he/she sets the org.freebsd:swap=on property on the zvol to turn swap on. On Linux, a developer would create a vanilla zvol and set up swap like any other partition with mkswap and swapon. Under the latest versions of all three operating systems mentioned, the Zpool version is at the same level, which is to say based on zpool v28 with additional features added by way of feature flags. They are compatible, users can create a zpool on Illumos/OmniOS, use it, export it, move the disks to a FreeBSD server, import the zpool, use it, export it, move to a Linux server, import the zpool, use it, etc. This exact scenario is something we have done at OmniTI and it worked without a hitch. One issue however is that the ACL support/usability is different on each OS so you'd the user will likely have to clean up the permissions a bit.

Caveats for Running ZFS on Arch Linux in a Production Environment
ZFS under Arch Linux is not part of the main package repository. As ZFS and its utilities are maintained by a third party, developers must rely on the third party to keep the packages up to date. One issue is that every time a new kernel is released (frequently) the ZFS kernel modules must be rebuilt as well. If the company upgrades its system (pacman -Syu) and reboots, but the ZFS modules were not recompiled well, Zpools will not initialize. This becomes especially important when developers have the rootfs under ZFS since this would leave the system unbootable and the user would be forced to recover by means of Rescue CD or, in the case of AWS, moving the EBS volumes to another instance and recovering from there. Linux does have a mechanism for automating this process other than DKMS. However, the arch zfs-modules-dkms package that provides this functionality is not kept up to date, and shouldn't be used.

Also, as briefly mentioned above, it should be noted that one cannot boot directly from ZFS on Linux, users must maintain a Linux bootloader compatible file system for /boot such as ext[234].

Currently, many of the utilities that output information about the filesystem are not ZFS aware and developers can get strange results running commands such as "df" for example, since it does not know the relationship between datasets and their parents. These will not necessarily prevent anything from running, but it is worth noting. Generally it's best to use "zfs list" rather than "df" to get accurate results.

ZFS natively uses NFSv4-style ACLs and is not compatible with Posix-style ACLs. Any applications that rely on Posix-style ACLs will have issues. Default GNU utilities like "ls" for example are not NFSv4 ACL aware.

Lastly, the ZoL project proclaims that ZFS on Linux is production ready, however it is worthwhile to note that it is still very immature at this point. ZFS itself has been around and tested for quite some time and is mature, so be careful and test before using it in a production environment.

How To Install ZFS on Arch with RootFS on ZFS
The Arch Wiki page for Installing Linux on ZFS goes into great detail on how to install Linux on ZFS. The key points are as follows:

  • The ZFS utilities and kernel modules must be built/installed prior to beginning the installation (within the CD Boot environment)
  • Even though you can have the Root FS on ZFS, the Linux bootloaders cannot load the kernel from ZFS currently so you still need a small ext2/3 partition for /boot to hold the kernel, the initramfs, and files that the bootloader requires.
  • There is no "beadm" in Linux to support multiple Boot Environment snapshots currently. One of the benefits of ZFS on Illumos/OmniOS is the ability to rollback to an earlier boot environment when applying updates.
  • When building the initramfs image, the zfs hook must come before the filesystems hook and you should not use the fsck hook at all.
  • You need to enable the ZFS service in systemd as this is not enabled by default. Under a ZFS Root system, this is very important if you like your systems to boot.
  • The "kernel" line of the bootloader needs to include a parameter telling the kernel where the root FS resides. For example, if the root FS is on a Zpool named "rpool" and its dataset is rpool/ROOT/default, then this parameter would be zfs=rpool/ROOT/default.

It is important to remember to export the zpool prior to rebooting after installation otherwise ZFS will complain that the system is different and will not import itself. This is because the new system is, in fact, a different system than the CD Media boot environment. Also, it's a very good idea to rebuild the initramfs (mkinitcpio -p linux) right away once you log into the installed system for the first time to avoid any "pool may be in use" errors due to differences in the CD Media Boot environment when the ramdisk was created initially.

Included at the end of this article are portions of a script used to build ArchLinux on ZFS. The only parts that have been removed are things that are specific to my environment. This is given as an example only to illustrate the steps that can be used, but note that it may or may not match the methods typically used for your environment.

Referencesz
ZFS on Linux Main Page: http://zfsonlinux.org

Arch Wiki - Installing Linux on ZFS: https://wiki.archlinux.org/index.php/Installing_Arch_Linux_on_ZFS

Arch Wiki - ZFS: https://wiki.archlinux.org/index.php/ZFS

Appendix A - Excerpts from Vagrant install script

The following are the commands we use when installing ZFS on ArchLinux under Vagrant. The Vagrant specific bits have been removed as they would not apply for installation on a production server. The full script can be found here: https://github.com/Loki22/scripts/blob/master/Vagrant/archzfs_vagrant_install.sh

pacman -Syy

pacman -S --noconfirm base-devel

mkdir /root/build

cd /root/build

wget https://aur.archlinux.org/packages/sp/spl-utils/spl-utils.tar.gz

wget https://aur.archlinux.org/packages/sp/spl/spl.tar.gz

wget https://aur.archlinux.org/packages/zf/zfs-utils/zfs-utils.tar.gz

wget https://aur.archlinux.org/packages/zf/zfs/zfs.tar.gz

for i in spl-utils spl zfs-utils zfs

do

cd /root/build && tar zxvf ${i}.tar.gz

cd /root/build/${i}

makepkg -s --asroot --noconfirm && pacman -U --noconfirm ./${i}*.pkg.tar.xz

done

# Install packages needed for ZFS

pacman -S --noconfirm archzfs dosfstools gptfdisk

# Clear the disk and initialize in GPT Format

sgdisk -o -g /dev/sda

# Partitioning - 3 Partitions (BIOS Boot Partition, /boot, and ZFS)

sgdisk -n 2:2048:+512M -c 2:"Linux Boot Partition" -t 2:8300 /dev/sda

sgdisk -n 3:0:0 -c 3:"ZFS Root Pool" -t 3:bf00 /dev/sda

sgdisk -n 1:34:2047 -c 1:"BIOS Boot Partition" -t 1:ef02 /dev/sda

# Create filesystem for /boot partition

mkfs.ext4 -L BOOT /dev/sda2

# Set up the ZFS Root Pool

modprobe zfs

zpool create rpool /dev/sda3

zfs set checksum=fletcher4 rpool

zfs set atime=off rpool

zfs set compression=lzjb rpool

zfs set mountpoint=none rpool

zpool export rpool

zpool import -d /dev/disk/by-id -R /mnt rpool

# Set up the initial BE (linux doesn't have beadm at this point, but not a bad idea to think ahead)

zfs create rpool/ROOT

zfs create -o mountpoint=/ rpool/ROOT/default

zpool set bootfs=rpool/ROOT/default rpool

# Set up datasets that are not part of the BE

zfs create -o mountpoint=/home -o setuid=off rpool/home

zfs create -o mountpoint=/root -o setuid=off rpool/roothome

# Create swap (example here is 2GB, use 4K block size for 64 bit systems)

zfs create -V 2G -b 4K rpool/swap

mkswap -Lswap -f /dev/rpool/swap

swapon /dev/rpool/swap

# Mount /boot

mkdir /mnt/boot

mount /dev/sda2 /mnt/boot

# Change ZFS repo to core now that we have it installed. This is so the new system will use updated modules linked to the new kernel as opposed to the somewhat more stale kernel that is used on the Install CD.

sed -i 's/demz-repo-archiso/demz-repo-core/' /etc/pacman.conf

# Bootstrap the new installation

pacstrap /mnt base base-devel archzfs sudo gnupg vim

# Generate the fstab minus the ZFS bits of which mounting is handled by ZFS

genfstab -U -p /mnt | grep boot >> /mnt/etc/fstab

# Configuration

CHROOT="arch-chroot /mnt"

# Hostname

echo "myhostname" > /mnt/etc/hostname

# Timezone and Clock

ln -s /usr/share/zoneinfo/America/New_York /mnt/etc/localtime

hwclock --systohc --utc

# Locale

sed -i 's/^#\(en_US.*\)/\1/' /mnt/etc/locale.gen

$CHROOT locale-gen

echo 'LANG="en_US.UTF-8"' > /mnt/etc/locale.conf

# Keymap

echo "KEYMAP=us" > /mnt/etc/vconsole.conf

# Mkinitcpio

sed -i 's/^\(HOOKS.*\)filesystems keyboard fsck/\1keyboard zfs filesystems/' /mnt/etc/mkinitcpio.conf

$CHROOT mkinitcpio -p linux

# Enable ZFS at boot

$CHROOT systemctl enable zfs.service

# Install GRUB

$CHROOT pacman -S --noconfirm grub-bios

modprobe dm-mod

$CHROOT grub-install --target=i386-pc --recheck --debug /dev/sda

cp /mnt/usr/share/locale/en\@quot/LC_MESSAGES/grub.mo /mnt/boot/grub/locale/en.mo

mv /mnt/boot/grub/grub.cfg /mnt/boot/grub/grub.cfg.orig

cat > /mnt/boot/grub/grub.cfg <<EOF

set timeout=2

set default=0

# (0) Arch Linux

menuentry "Arch Linux" {

set root=(hd0,2)

linux /vmlinuz-linux zfs=rpool/ROOT/default

initrd /initramfs-linux.img

}

# (1) Arch Linux (fallback)

menuentry "Arch Linux - Fallback" {

set root=(hd0,2)

linux /vmlinuz-linux zfs=rpool/ROOT/default

initrd /initramfs-linux-fallback.img

}

EOF

# SSH

$CHROOT pacman -S --noconfirm openssh

ln -s '/usr/lib/systemd/system/sshd.service' \

'/mnt/etc/systemd/system/multi-user.target.wants/sshd.service'

# Networking on installed system

# Manual linking because systemd isn't running yet

# Run 'ip link' to check the network interface and make sure it's enp0s3

ln -s '/usr/lib/systemd/system/dhcpcd@.service' \

'/mnt/etc/systemd/system/multi-user.target.wants/[email protected]'

# Clean up

# Remove downloaded packages

$CHROOT pacman -Scc --noconfirm

# Set your root password

passwd root

# Unmount filesystems, change ZFS mountpoints, and reboot

umount /mnt/boot

zfs umount -a

zpool export rpool

echo "If there were no errors, it would now be safe to reboot into the new system."

Appendix B - Recovery process if ZFS modules are not rebuilt on kernel upgrade
As mentioned above, the ZFS modules need to be rebuilt on every kernel upgrade. If this isn't done, you need to recover from a rescue environment. The recovery process (assuming booting from CD) is to build the ZFS modules/utils from the AUR (spl-utils, spl, zfs-utils, and zfs) in the temporary rescue environment, loading the ZFS module, mounting the Zpool under /mnt, mounting the /boot FS at /mnt/boot, chrooting, building the ZFS modules/utils again against the kernel in the chroot environment, rebuilding initramfs (mkinitcpio -p linux), and rebooting. Needless to say, not fun while people are screaming at you because the production server is down. This problem will be alleviated at some point when the ZFS packages are adopted into the main repositories and maintained with the rest of the release process.

More Stories By Kevin Loukinen

Kevin Loukinen is Site Reliability Engineer at OmniTI. Prior to that, he worked both as a Systems Administrator and Network Administrator for more than 12 years across several industries (financial, government and telecommunications).

Comments (0)

Share your thoughts on this story.

Add your comment
You must be signed in to add a comment. Sign-in | Register

In accordance with our Comment Policy, we encourage comments that are on topic, relevant and to-the-point. We will remove comments that include profanity, personal attacks, racial slurs, threats of violence, or other inappropriate material that violates our Terms and Conditions, and will block users who make repeated violations. We ask all readers to expect diversity of opinion and to treat one another with dignity and respect.


@ThingsExpo Stories
GENBAND has announced that SageNet is leveraging the Nuvia platform to deliver Unified Communications as a Service (UCaaS) to its large base of retail and enterprise customers. Nuvia’s cloud-based solution provides SageNet’s customers with a full suite of business communications and collaboration tools. Two large national SageNet retail customers have recently signed up to deploy the Nuvia platform and the company will continue to sell the service to new and existing customers. Nuvia’s capabilities include HD voice, video, multimedia messaging, mobility, conferencing, Web collaboration, deskt...
The WebRTC Summit 2014 New York, to be held June 9-11, 2015, at the Javits Center in New York, NY, announces that its Call for Papers is open. Topics include all aspects of improving IT delivery by eliminating waste through automated business models leveraging cloud technologies. WebRTC Summit is co-located with 16th International Cloud Expo, @ThingsExpo, Big Data Expo, and DevOps Summit.
SYS-CON Media announced today that @WebRTCSummit Blog, the largest WebRTC resource in the world, has been launched. @WebRTCSummit Blog offers top articles, news stories, and blog posts from the world's well-known experts and guarantees better exposure for its authors than any other publication. @WebRTCSummit Blog can be bookmarked ▸ Here @WebRTCSummit conference site can be bookmarked ▸ Here
SYS-CON Events announced today that Cisco, the worldwide leader in IT that transforms how people connect, communicate and collaborate, has been named “Gold Sponsor” of SYS-CON's 16th International Cloud Expo®, which will take place on June 9-11, 2015, at the Javits Center in New York City, NY. Cisco makes amazing things happen by connecting the unconnected. Cisco has shaped the future of the Internet by becoming the worldwide leader in transforming how people connect, communicate and collaborate. Cisco and our partners are building the platform for the Internet of Everything by connecting the...
Temasys has announced senior management additions to its team. Joining are David Holloway as Vice President of Commercial and Nadine Yap as Vice President of Product. Over the past 12 months Temasys has doubled in size as it adds new customers and expands the development of its Skylink platform. Skylink leads the charge to move WebRTC, traditionally seen as a desktop, browser based technology, to become a ubiquitous web communications technology on web and mobile, as well as Internet of Things compatible devices.
SYS-CON Events announced today that robomq.io will exhibit at SYS-CON's @ThingsExpo, which will take place on June 9-11, 2015, at the Javits Center in New York City, NY. robomq.io is an interoperable and composable platform that connects any device to any application. It helps systems integrators and the solution providers build new and innovative products and service for industries requiring monitoring or intelligence from devices and sensors.
Wearable technology was dominant at this year’s International Consumer Electronics Show (CES) , and MWC was no exception to this trend. New versions of favorites, such as the Samsung Gear (three new products were released: the Gear 2, the Gear 2 Neo and the Gear Fit), shared the limelight with new wearables like Pebble Time Steel (the new premium version of the company’s previously released smartwatch) and the LG Watch Urbane. The most dramatic difference at MWC was an emphasis on presenting wearables as fashion accessories and moving away from the original clunky technology associated with t...
Docker is an excellent platform for organizations interested in running microservices. It offers portability and consistency between development and production environments, quick provisioning times, and a simple way to isolate services. In his session at DevOps Summit at 16th Cloud Expo, Shannon Williams, co-founder of Rancher Labs, will walk through these and other benefits of using Docker to run microservices, and provide an overview of RancherOS, a minimalist distribution of Linux designed expressly to run Docker. He will also discuss Rancher, an orchestration and service discovery platf...
SYS-CON Events announced today that Akana, formerly SOA Software, has been named “Bronze Sponsor” of SYS-CON's 16th International Cloud Expo® New York, which will take place June 9-11, 2015, at the Javits Center in New York City, NY. Akana’s comprehensive suite of API Management, API Security, Integrated SOA Governance, and Cloud Integration solutions helps businesses accelerate digital transformation by securely extending their reach across multiple channels – mobile, cloud and Internet of Things. Akana enables enterprises to share data as APIs, connect and integrate applications, drive part...
SYS-CON Events announced today that Vitria Technology, Inc. will exhibit at SYS-CON’s @ThingsExpo, which will take place on June 9-11, 2015, at the Javits Center in New York City, NY. Vitria will showcase the company’s new IoT Analytics Platform through live demonstrations at booth #330. Vitria’s IoT Analytics Platform, fully integrated and powered by an operational intelligence engine, enables customers to rapidly build and operationalize advanced analytics to deliver timely business outcomes for use cases across the industrial, enterprise, and consumer segments.
SYS-CON Events announced today that Solgenia will exhibit at SYS-CON's 16th International Cloud Expo®, which will take place on June 9-11, 2015, at the Javits Center in New York City, NY, and the 17th International Cloud Expo®, which will take place on November 3–5, 2015, at the Santa Clara Convention Center in Santa Clara, CA. Solgenia is the global market leader in Cloud Collaboration and Cloud Infrastructure software solutions. Designed to “Bridge the Gap” between Personal and Professional Social, Mobile and Cloud user experiences, our solutions help large and medium-sized organizations dr...
SYS-CON Events announced today that Liaison Technologies, a leading provider of data management and integration cloud services and solutions, has been named "Silver Sponsor" of SYS-CON's 16th International Cloud Expo®, which will take place on June 9-11, 2015, at the Javits Center in New York, NY. Liaison Technologies is a recognized market leader in providing cloud-enabled data integration and data management solutions to break down complex information barriers, enabling enterprises to make smarter decisions, faster.
Cloud is not a commodity. And no matter what you call it, computing doesn’t come out of the sky. It comes from physical hardware inside brick and mortar facilities connected by hundreds of miles of networking cable. And no two clouds are built the same way. SoftLayer gives you the highest performing cloud infrastructure available. One platform that takes data centers around the world that are full of the widest range of cloud computing options, and then integrates and automates everything. Join SoftLayer on June 9 at 16th Cloud Expo to learn about IBM Cloud's SoftLayer platform, explore se...
@ThingsExpo has been named the Top 5 Most Influential M2M Brand by Onalytica in the ‘Machine to Machine: Top 100 Influencers and Brands.' Onalytica analyzed the online debate on M2M by looking at over 85,000 tweets to provide the most influential individuals and brands that drive the discussion. According to Onalytica the "analysis showed a very engaged community with a lot of interactive tweets. The M2M discussion seems to be more fragmented and driven by some of the major brands present in the M2M space. This really allows some room for influential individuals to create more high value inter...
The world's leading Cloud event, Cloud Expo has launched Microservices Journal on the SYS-CON.com portal, featuring over 19,000 original articles, news stories, features, and blog entries. DevOps Journal is focused on this critical enterprise IT topic in the world of cloud computing. Microservices Journal offers top articles, news stories, and blog posts from the world's well-known experts and guarantees better exposure for its authors than any other publication. Follow new article posts on Twitter at @MicroservicesE
SYS-CON Events announced today the IoT Bootcamp – Jumpstart Your IoT Strategy, being held June 9–10, 2015, in conjunction with 16th Cloud Expo and Internet of @ThingsExpo at the Javits Center in New York City. This is your chance to jumpstart your IoT strategy. Combined with real-world scenarios and use cases, the IoT Bootcamp is not just based on presentations but includes hands-on demos and walkthroughs. We will introduce you to a variety of Do-It-Yourself IoT platforms including Arduino, Raspberry Pi, BeagleBone, Spark and Intel Edison. You will also get an overview of cloud technologies s...
SYS-CON Events announced today that SafeLogic has been named “Bag Sponsor” of SYS-CON's 16th International Cloud Expo® New York, which will take place June 9-11, 2015, at the Javits Center in New York City, NY. SafeLogic provides security products for applications in mobile and server/appliance environments. SafeLogic’s flagship product CryptoComply is a FIPS 140-2 validated cryptographic engine designed to secure data on servers, workstations, appliances, mobile devices, and in the Cloud.
Containers and microservices have become topics of intense interest throughout the cloud developer and enterprise IT communities. Accordingly, attendees at the upcoming 16th Cloud Expo at the Javits Center in New York June 9-11 will find fresh new content in a new track called PaaS | Containers & Microservices Containers are not being considered for the first time by the cloud community, but a current era of re-consideration has pushed them to the top of the cloud agenda. With the launch of Docker's initial release in March of 2013, interest was revved up several notches. Then late last...
SOA Software has changed its name to Akana. With roots in Web Services and SOA Governance, Akana has established itself as a leader in API Management and is expanding into cloud integration as an alternative to the traditional heavyweight enterprise service bus (ESB). The company recently announced that it achieved more than 90% year-over-year growth. As Akana, the company now addresses the evolution and diversification of SOA, unifying security, management, and DevOps across SOA, APIs, microservices, and more.
After making a doctor’s appointment via your mobile device, you receive a calendar invite. The day of your appointment, you get a reminder with the doctor’s location and contact information. As you enter the doctor’s exam room, the medical team is equipped with the latest tablet containing your medical history – he or she makes real time updates to your medical file. At the end of your visit, you receive an electronic prescription to your preferred pharmacy and can schedule your next appointment.