Welcome!

Java IoT Authors: Yeshim Deniz, Elizabeth White, Pat Romanski, Carmen Gonzalez, Liz McMillan

Related Topics: Linux Containers, Open Source Cloud, Containers Expo Blog

Linux Containers: 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' \

[email protected]rvice'

# 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
SYS-CON Events announced today that Tappest will exhibit MooseFS at SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. MooseFS is a breakthrough concept in the storage industry. It allows you to secure stored data with either duplication or erasure coding using any server. The newest – 4.0 version of the software enables users to maintain the redundancy level with even 50% less hard drive space required. The software func...
SYS-CON Events announced today that Interoute, owner-operator of one of Europe's largest networks and a global cloud services platform, has been named “Bronze Sponsor” of SYS-CON's 20th Cloud Expo, which will take place on June 6-8, 2017 at the Javits Center in New York, New York. Interoute is the owner-operator of one of Europe's largest networks and a global cloud services platform which encompasses 12 data centers, 14 virtual data centers and 31 colocation centers, with connections to 195 add...
SYS-CON Events announced today that EARP will exhibit at SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. "We are a software house, so we perfectly understand challenges that other software houses face in their projects. We can augment a team, that will work with the same standards and processes as our partners' internal teams. Our teams will deliver the same quality within the required time and budget just as our partn...
Most technology leaders, contemporary and from the hardware era, are reshaping their businesses to do software in the hope of capturing value in IoT. Although IoT is relatively new in the market, it has already gone through many promotional terms such as IoE, IoX, SDX, Edge/Fog, Mist Compute, etc. Ultimately, irrespective of the name, it is about deriving value from independent software assets participating in an ecosystem as one comprehensive solution.
SYS-CON Events announced today that delaPlex will exhibit at SYS-CON's @ThingsExpo, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. delaPlex pioneered Software Development as a Service (SDaaS), which provides scalable resources to build, test, and deploy software. It’s a fast and more reliable way to develop a new product or expand your in-house team.
SYS-CON Events announced today that Systena America will exhibit at SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. Systena Group has been in business for various software development and verification in Japan, US, ASEAN, and China by utilizing the knowledge we gained from all types of device development for various industries including smartphones (Android/iOS), wireless communication, security technology and IoT serv...
Amazon started as an online bookseller 20 years ago. Since then, it has evolved into a technology juggernaut that has disrupted multiple markets and industries and touches many aspects of our lives. It is a relentless technology and business model innovator driving disruption throughout numerous ecosystems. Amazon’s AWS revenues alone are approaching $16B a year making it one of the largest IT companies in the world. With dominant offerings in Cloud, IoT, eCommerce, Big Data, AI, Digital Assista...
SYS-CON Events announced today that Outscale will exhibit at SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. Outscale's technology makes an automated and adaptable Cloud available to businesses, supporting them in the most complex IT projects while controlling their operational aspects. You boost your IT infrastructure's reactivity, with request responses that only take a few seconds.
Everywhere we turn in our industry we can find strong opinions about the direction, type and nature of cloud’s impact on computing and business. Another word that is used in every context in our industry is “hybrid.” In his session at 20th Cloud Expo, Alvaro Gonzalez, Director of Technical, Partner and Field Marketing at Peak 10, will use a combination of a few conceptual props and some research recently commissioned by Peak 10 to offer a real-world consideration of how the various categories of...
In his keynote at @ThingsExpo, Chris Matthieu, Director of IoT Engineering at Citrix and co-founder and CTO of Octoblu, focused on building an IoT platform and company. He provided a behind-the-scenes look at Octoblu’s platform, business, and pivots along the way (including the Citrix acquisition of Octoblu).
DevOps at Cloud Expo – being held October 31 - November 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA – announces that its Call for Papers is open. Born out of proven success in agile development, cloud computing, and process automation, DevOps is a macro trend you cannot afford to miss. From showcase success stories from early adopters and web-scale businesses, DevOps is expanding to organizations of all sizes, including the world's largest enterprises – and delivering real r...
Five years ago development was seen as a dead-end career, now it’s anything but – with an explosion in mobile and IoT initiatives increasing the demand for skilled engineers. But apart from having a ready supply of great coders, what constitutes true ‘DevOps Royalty’? It’ll be the ability to craft resilient architectures, supportability, security everywhere across the software lifecycle. In his keynote at @DevOpsSummit at 20th Cloud Expo, Jeffrey Scheaffer, GM and SVP, Continuous Delivery Busine...
SYS-CON Events announced today that Outscale, a global pure play Infrastructure as a Service provider and strategic partner of Dassault Systèmes, will exhibit at SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. Founded in 2010, Outscale simplifies infrastructure complexities and boosts the business agility of its customers. Outscale delivers a secure, reliable and industrial strength solution for its customers, which in...
SYS-CON Events announced today that CollabNet, a global leader in enterprise software development, release automation and DevOps solutions, will be a Bronze Sponsor of SYS-CON's 20th International Cloud Expo®, taking place from June 6-8, 2017, at the Javits Center in New York City, NY. CollabNet offers a broad range of solutions with the mission of helping modern organizations deliver quality software at speed. The company’s latest innovation, the DevOps Lifecycle Manager (DLM), supports Value S...
SYS-CON Events announced today that Peak 10, Inc., a national IT infrastructure and cloud services provider, will exhibit at SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. Peak 10 provides reliable, tailored data center and network services, cloud and managed services. Its solutions are designed to scale and adapt to customers’ changing business needs, enabling them to lower costs, improve performance and focus intern...
A strange thing is happening along the way to the Internet of Things, namely far too many devices to work with and manage. It has become clear that we'll need much higher efficiency user experiences that can allow us to more easily and scalably work with the thousands of devices that will soon be in each of our lives. Enter the conversational interface revolution, combining bots we can literally talk with, gesture to, and even direct with our thoughts, with embedded artificial intelligence, whic...
In order to meet the rapidly changing demands of today’s customers, companies are continually forced to redefine their business strategies in order to meet these needs, stay relevant and continue to see profitable growth. IoT deployment and development is integral in this transformation, and today businesses are increasingly seeing the value of investing their resources into IoT deployments. These technologies are able increase ROI through projects such as connecting supply chains or enabling sm...
In his opening keynote at 20th Cloud Expo, Michael Maximilien, Research Scientist, Architect, and Engineer at IBM, will motivate why realizing the full potential of the cloud and social data requires artificial intelligence. By mixing Cloud Foundry and the rich set of Watson services, IBM's Bluemix is the best cloud operating system for enterprises today, providing rapid development and deployment of applications that can take advantage of the rich catalog of Watson services to help drive insigh...
SYS-CON Events announced today that Super Micro Computer, Inc., a global leader in compute, storage and networking technologies, will exhibit at SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. Supermicro (NASDAQ: SMCI), the leading innovator in high-performance, high-efficiency server technology, is a premier provider of advanced server Building Block Solutions® for Data Center, Cloud Computing, Enterprise IT, Hadoop/...
SYS-CON Events announced today that SoftLayer, an IBM Company, has been named “Gold Sponsor” of SYS-CON's 18th Cloud Expo, which will take place on June 7-9, 2016, at the Javits Center in New York, New York. SoftLayer, an IBM Company, provides cloud infrastructure as a service from a growing number of data centers and network points of presence around the world. SoftLayer’s customers range from Web startups to global enterprises.