Setting-up a Zoned Storage Compatible Linux System

Overview

The first step in getting zoned storage working is setting up a Linux system that is compatible with zoned storage. Such a system has the following components:

1. A compatible Linux distribution with the right kernel version
2. Support for zoned block devices
3. Necessary system utilities

Follow the instructions on this page to set up a zoned-storage compatible system. Click on each of the links above in turn and follow the instructions to set up a Linux system for zoned storage.

Linux Distribution

Overview

The zoned block device (ZBD) interface that supports SCSI ZBC and ATA ZAC disks was added to the Linux® kernel in version 4.10. Zoned Namespace (ZNS) devices are supported from kernel version 5.9 (inclusive). All Linux kernel versions higher than 5.9 support zoned storage devices.

note

Linux kernels prior to version 4.10 do not implement the zoned block device interface. If you use a kernel older than kernel 4.10, you can access and manage SCSI ZBC and ATA ZAC disks, but only in a limited way. This is discussed in more detail in the Linux Support document.

To verify that a zoned block device has been discovered and correctly initalized, several user utilities must be installed on the test system. These utilities are discussed in more detail in the section called System Utilities.

It is possible to configure, compile, and install your own kernel, but this is not recommended for people without prior experience of kernel configuration. If this is your first time setting up a zoned-storage-compatible Linux system, use one of the recommended Linux distributions.

More advanced users might prefer to modify their preferred system by compiling a zoned-storage-compatible kernel and installing it from source, and then installing all necessary user packages.

Recommended Linux Distributions

Some Linux distributions provide zoned-storage support out of the box (without any modification). A regular installation of any of these distributions provides a system that is ready to use with SMR hard disks and SSDs with ZNS support.

• Fedora 36 or above

• Latest openSUSE Tumbleweed

These distributions are "rolling release" Linux distributions. They provide the most recent stable Linux kernel, they have zoned block device support enabled, and they have all the system user packages (e.g. Linux system utilities) necessary to support zoned storage.

Installation instructions are available on the website of each distribution. The installation of these distributions is beyond the scope of this Zoned Storage documentation.

Modifying a Linux Distribution Installation

Linux systems that are not on the Recommended Distributions list do not support zoned storage by default, but some of them can be modified to provide some level of support for zoned storage. More information about the level of support provided by these Linux distributions can be found on the Linux Distributions page.

If you know what you're doing, you can modify your preferred Linux distribution to enable or improve its support for zoned storage.

Two conditions must be met to ensure that a system's Linux kernel supports the zoned block device interface.

1. The kernel version must be 4.10.0 or higher.

2. The kernel configuration option CONFIG_BLK_DEV_ZONED must be enabled.

Checking the Kernel Version

The command uname makes it possible to check the version of the kernel running on a system. For example, on a Fedora 36 distribution, this command and its output is as follows.

# uname -r
5.18.11-200.fc36.x86_64

If the system kernel version is older than version 4.10, the kernel must be upgraded to a more recent version to gain zoned block device support.

Checking Zoned Block Device Support

Zoned block device support might not be enabled by default in the running kernel. The kernel configuration option that is used to enable zoned block device support is CONFIG_BLK_DEV_ZONED.

Several methods can be used to determine whether the option CONFIG_BLK_DEV_ZONED has been enabled in the kernel. Not all of these methods work for every Linux distribution. In some distributions, the configuration file for the running kernel can be found in the /boot directory or in the directory containing the kernel modules.

The following commands test whether your installed kernel supports zoned block devices.

# cat /boot/config-`uname -r` | grep CONFIG_BLK_DEV_ZONED
CONFIG_BLK_DEV_ZONED=y

or

# cat /lib/modules/`uname -r`/config | grep CONFIG_BLK_DEV_ZONED
CONFIG_BLK_DEV_ZONED=y

If the output of one of these commands is CONFIG_BLK_DEV_ZONED=y, then zoned block devices are supported by the kernel. If the output is CONFIG_BLK_DEV_ZONED=n, then block device support is disabled and the kernel must be recompiled in order to enable block device support.

note

For kernels older than kernel version 4.10, the output of these commands is always empty. Kernels older than kernel version 4.10 do not support zoned block devices.

If your kernel exports its configuration through the proc file system, use one of the following sets of commands to retreive the status of CONFIG_BLK_DEV_ZONED:

# modprobe configs
# cat /proc/config.gz | gunzip | grep CONFIG_BLK_DEV_ZONED
CONFIG_BLK_DEV_ZONED=y

or

# modprobe configs
# zcat /proc/config.gz | grep CONFIG_BLK_DEV_ZONED
CONFIG_BLK_DEV_ZONED=y

Kernel Upgrade

If either the system kernel version is too old or if the kernel does not have zoned block device support, a new Linux kernel must be configured, compiled and installed to support zoned block devices.

Learn how to enable zoned block device support in the kernel configuration here. We recommend that you always use the highest-available stable kernel version or a recent long-term-stable kernel version higher than 4.10. Information on available long term and stable kernel versions can be found here.

Checking a System's Configuration

A Linux system properly configured for zoned block device support has the following:

1. A kernel that supports zoned block devices
2. Proper zoned device configuration
3. (in some cases) System utliities that provide zoned block device information.

Write Ordering Control

By default, the Linux kernel does not guarantee the order in which commands are delivered to a block device. This means that an application that writes sequentially to a disk might have its write commands delivered to the disk in a different order than the order sent by the application. This might cause write errors if the application is writing to sequential write required zones of a zoned device.

To avoid this problem, a "zone write lock mechanism" that serializes writes to sequential zones is implemented by all kernels that support zoned block devices. For kernel versions between 4.10 and 4.15 (inclusive) no special configuration is necessary and the kernel guarantees the delivery of write commands to the device in the same order as the order of write requests issued by the application.

In kernel version 4.16, the implementation of zone write locking was moved to the deadline and mq-deadline block I/O scheduler. Therefore, in kernels of version 4.16 and higher, you must use this scheduler with zoned block devices in order to make the kernel guarantee the order of write commands.

note

The mq-deadline block I/O scheduler is enabled only if the SCSI multi-queue (scsi-mq) infrastructure is enabled. This feature use can be controlled by using the kernel boot argument scsi_mod.use_blk_mq. scsi-mq is always enabled by default since kernel version 5.0 and the legacy single-queue SCSI command path (deadline scheduler) is no longer supported.

To see which block I/O scheduler a zoned disk uses, run the following command:

# cat /sys/block/sdb/queue/scheduler
[none] mq-deadline kyber bfq

If the disk block I/O scheduler that has been selected is not mq-deadline as in the example above, use the following command to change the scheduler:

# echo mq-deadline > /sys/block/sdb/queue/scheduler

# cat sys/block/sdb/queue/scheduler
[mq-deadline] kyber bfq none

System Utilities

Certain system utilities should be installed on the system in order to verify the correct operation of zoned block devices and to troubleshoot problems.

If one of the recommended Linux distributions is being used, these utilities are installed by default.

lsblk and blkzone

The lsblk command in Linux lists block devices, which includes zoned block devices. Some usage examples are provided in the lsblk section of the tools documentation page.

The blkzone utility lists (reports) the zones of a zoned block device and makes it possible to reset the write pointer position of a range of zones in the device. blkzone also allows executing other zone management functions such as opening, closing and finishing a zone.

blkzone usage examples are provided in the blkzone section of the tools documentation page.

Both lsblk and blkzone are part of the util-linux package, which is installed by default on most Linux distributions. However, the zone block device support for these utilities (and so the existence of the blkzone utility itself) depend on wether the Linux distribution used supports zoned block devices. If the kernel was manually upgraded to enable zoned block device support, the util-linux package must also be compiled and installed manually to match the zoned block device support of the new kernel.

Information on the util-linux package can be found here.

lsscsi

The lsscsi command lists information about the SCSI devices connected to a Linux system. lsscsi is generally available as a package in most Linux distributions. Refer to your distribution documentation to find the name of the package that provides the lsscsi utility.

The SCSI Generic Utilities document provides more information and usage examples of lssci.

sg3_utils

The sg3_utils package is a collection of command line tools that send SCSI commands to a SCSI device.

In Linux, all disks are exposed as SCSI disks. This includes ATA drives. sg3_utils can be used to manage SAS ZBC disks as well as SATA ZAC disks. When dealing with SATA disks connected to SATA ports (for example, an AHCI adapter), the kernel ATA subsystem (libata) translates SCSI commands into ATA commands.

sg3_utils includes three command line tools specific to ZBC disks:

Utility Name	SCSI Command Invoked	Description
sg_rep_zones	REPORT ZONES	Get the ZBC disk's zone information
sg_reset_wp	RESET WRITE POINTER	Reset one zone or all zones of the ZBC disk
sg_zone	CLOSE ZONE, FINISH ZONE, OPEN ZONE	Sends one of these commands to the given ZBC disk

This section shows some examples of these utilities execution.