This is going to be a two part article where in the first part I will give you an overview to install and configure stratis on RHEL 8 Linux host which includes installing pre-requisite rpms and starting required daemon services, creating pools, thin provisioned file systems and mounting these file systems to access and store our data. In the next article I will share the steps to create, modify and remove snapshot for a stratis file system/pool along with other stratis related commands using RHEL 8 Linux.
Understanding Stratis
Stratis is a called Volume Managing file system, and it is Red Hat's answer to Btrfs and ZFS. Volume managing file system means that it works with the notion of volumes as well. So it's a layer in between the regular file system and the storage devices. And on top of Stratis a regular file system is needed.
Stratis is built on top of any block device, and that includes LVM devices, which is interesting because Stratis is working with the notion of volumes and you know that the LVM is working with the notion of volumes as well. So you can configure Stratis in a way that on your server you will have volumes at two different levels.
The pool enables many useful advanced features, such as:
- File system snapshots
- Thin provisioning
- Cache Tier - It works with cache tier, which means that it is handling caching in a very efficient way.
- Programmatic API - which means that applications can directly address the Stratis process to configure storage.
Stratis Architecture
- On the top in the Stratis architecture, there's pool. A pool is created from one or more storage devices, which are known as blockdev, Now blockdev are basically block devices, such as a disk or a disk partition.
- Stratis will create a
/dev/stratis/my-pooldirectory for each pool and this directory contains links to the devices that represent the file systems in the pool. Here pool is composed of one or more block devices. - A pool has a fixed total size, equal to the size of the block devices. Block devices in a pool may not be thin provisioned.
- Thin provisioning is happening at the file system level.
- The XFS file system is put in a volume on top of the pool and it's an integrated part of it. So file system and volume are a bundle, they come together.
- Each pool can contain one or more file systems.
- And file systems are thin provisioned, and they do not have a fixed size.
- Every file system can just grow to the size of the pool.
- The thin provisioned volume, which is an integrated part of the file system, automatically grows as more data is added to the file system
Installing on RHEL 8 Linux
This procedure installs all packages necessary to use Stratis using RHEL 8 vanilla DVD I used for installation of the operating system. I will be using RHEL 8 Linux node to demonstrate the steps in this article.
[root@node4 dvd]# yum install stratis-cli stratisd Updating Subscription Management repositories. Last metadata expiration check: 0:00:44 ago on Mon 17 Jun 2019 11:55:57 AM IST. Dependencies resolved. =================================================================================================================================================================== Package Arch Version Repository Size =================================================================================================================================================================== Installing: stratis-cli noarch 1.0.0-2.el8 rhel_dvd_appstream 50 k stratisd x86_64 1.0.0-2.el8 rhel_dvd_appstream 1.2 M Installing dependencies: python3-dbus-client-gen noarch 0.3-1.el8 rhel_dvd_appstream 25 k python3-dbus-python-client-gen noarch 0.6-2.el8 rhel_dvd_appstream 24 k python3-dbus-signature-pyparsing noarch 0.03-2.el8 rhel_dvd_appstream 19 k python3-into-dbus-python noarch 0.06-2.el8 rhel_dvd_appstream 27 k python3-justbases noarch 0.9-6.el8 rhel_dvd_appstream 45 k python3-justbytes noarch 0.11-2.el8 rhel_dvd_appstream 40 k python3-pyparsing noarch 2.1.10-7.el8 rhel_dvd_baseos 142 k Transaction Summary =================================================================================================================================================================== Install 9 Packages Total size: 1.5 M Installed size: 5.0 M Is this ok [y/N]: y Downloading Packages: Running transaction check Transaction check succeeded. Running transaction test Transaction test succeeded. Running transaction Preparing : 1/1 Installed: python3-pyparsing-2.1.10-7.el8.noarch Installing : python3-pyparsing-2.1.10-7.el8.noarch 1/9 Installed: python3-pyparsing-2.1.10-7.el8.noarch Installed: python3-dbus-signature-pyparsing-0.03-2.el8.noarch Installing : python3-dbus-signature-pyparsing-0.03-2.el8.noarch 2/9 Installed: python3-dbus-signature-pyparsing-0.03-2.el8.noarch Installed: python3-into-dbus-python-0.06-2.el8.noarch Installing : python3-into-dbus-python-0.06-2.el8.noarch 3/9 Installed: python3-into-dbus-python-0.06-2.el8.noarch Installed: python3-dbus-python-client-gen-0.6-2.el8.noarch Installing : python3-dbus-python-client-gen-0.6-2.el8.noarch 4/9 Installed: python3-dbus-python-client-gen-0.6-2.el8.noarch Installed: stratisd-1.0.0-2.el8.x86_64 Installing : stratisd-1.0.0-2.el8.x86_64 5/9 Running scriptlet: stratisd-1.0.0-2.el8.x86_64 5/9 Installed: stratisd-1.0.0-2.el8.x86_64 Installed: python3-justbases-0.9-6.el8.noarch Installing : python3-justbases-0.9-6.el8.noarch 6/9 Installed: python3-justbases-0.9-6.el8.noarch Installed: python3-justbytes-0.11-2.el8.noarch Installing : python3-justbytes-0.11-2.el8.noarch 7/9 Installed: python3-justbytes-0.11-2.el8.noarch Installed: python3-dbus-client-gen-0.3-1.el8.noarch Installing : python3-dbus-client-gen-0.3-1.el8.noarch 8/9 Installed: python3-dbus-client-gen-0.3-1.el8.noarch Installed: stratis-cli-1.0.0-2.el8.noarch Installing : stratis-cli-1.0.0-2.el8.noarch 9/9 Installed: stratis-cli-1.0.0-2.el8.noarch Running scriptlet: stratis-cli-1.0.0-2.el8.noarch 9/9 Verifying : python3-dbus-client-gen-0.3-1.el8.noarch 1/9 Verifying : python3-dbus-python-client-gen-0.6-2.el8.noarch 2/9 Verifying : python3-dbus-signature-pyparsing-0.03-2.el8.noarch 3/9 Verifying : python3-into-dbus-python-0.06-2.el8.noarch 4/9 Verifying : python3-justbases-0.9-6.el8.noarch 5/9 Verifying : python3-justbytes-0.11-2.el8.noarch 6/9 Verifying : stratis-cli-1.0.0-2.el8.noarch 7/9 Verifying : stratisd-1.0.0-2.el8.x86_64 8/9 Verifying : python3-pyparsing-2.1.10-7.el8.noarch 9/9 Installed: stratis-cli-1.0.0-2.el8.noarch stratisd-1.0.0-2.el8.x86_64 python3-dbus-client-gen-0.3-1.el8.noarch python3-dbus-python-client-gen-0.6-2.el8.noarch python3-dbus-signature-pyparsing-0.03-2.el8.noarch python3-into-dbus-python-0.06-2.el8.noarch python3-justbases-0.9-6.el8.noarch python3-justbytes-0.11-2.el8.noarch python3-pyparsing-2.1.10-7.el8.noarch Complete!
Make sure that the stratisd service is enabled and running
[root@node4 dvd]# systemctl enable --now stratisd
Created symlink /etc/systemd/system/sysinit.target.wants/stratisd.service → /usr/lib/systemd/system/stratisd.service.
[root@node4 dvd]# systemctl status stratisd
● stratisd.service - A daemon that manages a pool of block devices to create flexible file systems
Loaded: loaded (/usr/lib/systemd/system/stratisd.service; enabled; vendor preset: disabled)
Active: active (running) since Mon 2019-06-17 11:57:24 IST; 10s ago
Docs: man:stratisd(8)
Main PID: 11631 (stratisd)
Tasks: 1 (limit: 24008)
Memory: 756.0K
CGroup: /system.slice/stratisd.service
└─11631 /usr/libexec/stratisd --debug
Jun 17 11:57:24 node4.example systemd[1]: Started A daemon that manages a pool of block devices to create flexible file systems.
Jun 17 11:57:24 node4.example stratisd[11631]: DEBUG libstratis::stratis::buff_log: BuffLogger: pass_through: true hold time: none
Jun 17 11:57:24 node4.example stratisd[11631]: INFO stratisd: Using StratEngine
Jun 17 11:57:24 node4.example stratisd[11631]: DEBUG stratisd: Engine state:
Jun 17 11:57:24 node4.example stratisd[11631]: StratEngine {
Jun 17 11:57:24 node4.example stratisd[11631]: pools: {},
Jun 17 11:57:24 node4.example stratisd[11631]: incomplete_pools: {},
Jun 17 11:57:24 node4.example stratisd[11631]: watched_dev_last_event_nrs: {}
Jun 17 11:57:24 node4.example stratisd[11631]: }
Jun 17 11:57:24 node4.example stratisd[11631]: INFO stratisd: DBUS API is now available
Pre-requisites
Now our service is up and running successfully. Next we need devices on which we will create the stratis file system. Here I have added three virtual disks on my RHEL 8 virtual machine.
[root@node4 ~]# lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sda 8:0 0 8G 0 disk
├─sda1 8:1 0 512M 0 part /boot
└─sda2 8:2 0 7.5G 0 part
├─rhel-root 253:0 0 6.6G 0 lvm /
└─rhel-swap 253:1 0 956M 0 lvm [SWAP]
sdb 8:16 0 2G 0 disk
sdc 8:32 0 2G 0 disk
sdd 8:48 0 2G 0 disk
sr0 11:0 1 6.5G 0 rom
sr1 11:1 1 1024M 0 rom
If the selected block device contains file system, partition table, or RAID signatures, erase them:
[root@node4 ~]# wipefs -a /dev/sdb /dev/sdc /dev/sdd
To create a Stratis pool on the block device, use:
[root@node4 ~]# stratis pool create my-pool /dev/sdb /dev/sdc
Here I am creating a new pool with the name "my-pool" which will contain /dev/sdb and /dev/sdc block devices
To check the list of block devices part of stratis on your system:
[root@node4 ~]# stratis blockdev list Pool Name Device Node Physical Size State Tier my-pool /dev/sdb 2 GiB Not-in-use Data my-pool /dev/sdc 2 GiB In-use Data
To verify, list all pools on your system:
[root@node4 ~]# stratis pool list Name Total Physical Size Total Physical Used my-pool 4 GiB 56 MiB
Add block device to existing pool
Next to add one or more block devices to the existing pool, use:
[root@node4 ~]# stratis pool add-data my-pool /dev/sdd
Here I am adding /dev/sdd to my existing pool i.e. my-pool
Next verify the list of block devices part of stratis pool
[root@node4 ~]# stratis blockdev list Pool Name Device Node Physical Size State Tier my-pool /dev/sdb 2 GiB Not-in-use Data my-pool /dev/sdc 2 GiB In-use Data my-pool /dev/sdd 2 GiB Not-in-use Data
Create Stratis file system
This procedure creates a Stratis file system on an existing pool.
[root@node4 ~]# stratis filesystem create my-pool test-fs1 [root@node4 ~]# stratis filesystem create my-pool test-fs2
Here test-fs1 and test-fs2 are the two file systems which I have created under my-pool.
To verify, list file systems within the pool:
[root@node4 ~]# stratis filesystem list Pool Name Name Used Created Device my-pool test-fs1 546 MiB Jun 17 2019 12:05 /dev/stratis/my-pool/test-fs1 my-pool test-fs2 546 MiB Jun 17 2019 12:06 /dev/stratis/my-pool/test-fs2
You can also use below command to list the file systems available in the pool:
[root@node4 ~]# stratis fs list Pool Name Name Used Created Device my-pool test-fs1 546 MiB Jun 17 2019 12:05 /dev/stratis/my-pool/test-fs1 my-pool test-fs2 546 MiB Jun 17 2019 12:06 /dev/stratis/my-pool/test-fs2
Mount Stratis file system
This procedure mounts an existing Stratis file system to access the content. Currently my node contains the below partitions and file systems.
[root@node4 ~]# df -h Filesystem Size Used Avail Use% Mounted on devtmpfs 1.9G 0 1.9G 0% /dev tmpfs 1.9G 0 1.9G 0% /dev/shm tmpfs 1.9G 8.5M 1.9G 1% /run tmpfs 1.9G 0 1.9G 0% /sys/fs/cgroup /dev/mapper/rhel-root 6.4G 1.4G 4.8G 23% / /dev/sda1 488M 124M 329M 28% /boot tmpfs 379M 0 379M 0% /run/user/0
Now I will create new mount points for the two stratis file systems which we created above. I will create directories under / with below names
[root@node4 ~]# mkdir /test-fs1 [root@node4 ~]# mkdir /test-fs2
Now since I have two mount points available, use the entries that Stratis maintains in the /dev/stratis/ directory under "Device":
[root@node4 ~]# stratis fs list Pool Name Name Used Created Device my-pool test-fs1 546 MiB Jun 17 2019 12:05 /dev/stratis/my-pool/test-fs1 my-pool test-fs2 546 MiB Jun 17 2019 12:06 /dev/stratis/my-pool/test-fs2 [root@node4 ~]# mount /dev/stratis/my-pool/test-fs1 /test-fs1/ [root@node4 ~]# mount /dev/stratis/my-pool/test-fs2 /test-fs2/
To verify if the stratis file systems are successfully mounted:
[root@node4 ~]# df -h
Filesystem Size Used Avail Use% Mounted on
devtmpfs 1.9G 0 1.9G 0% /dev
tmpfs 1.9G 0 1.9G 0% /dev/shm
tmpfs 1.9G 8.5M 1.9G 1% /run
tmpfs 1.9G 0 1.9G 0% /sys/fs/cgroup
/dev/mapper/rhel-root 6.4G 1.4G 4.8G 23% /
/dev/sda1 488M 124M 329M 28% /boot
tmpfs 379M 0 379M 0% /run/user/0
/dev/mapper/stratis-1-a35d85c5802c49b59bb8c81104d43bb4-thin-fs-0f6d34239dcb4955803a1054c3a65972 1.0T 7.2G 1017G 1% /test-fs2
/dev/mapper/stratis-1-a35d85c5802c49b59bb8c81104d43bb4-thin-fs-bf11c663d9da4bc390a81440a9184312 1.0T 7.2G 1017G 1% /test-fs1
df reports the file system as 1 TB in size. This is because stratis file system do not have fixed size and they use thin provisioning so stratis will automatically resize these file system to grow on the space as needed.To check the space available in the pool
[root@node4 ~]# stratis pool list Name Total Physical Size Total Physical Used my-pool 6 GiB 1.12 GiB
So in this case total pool size is 6 GB and only 1.2 GB is used.
To check the space occupied by the file system:
[root@node4 ~]# stratis filesystem list Pool Name Name Used Created Device my-pool test-fs1 546 MiB Jun 17 2019 12:05 /dev/stratis/my-pool/test-fs1 my-pool test-fs2 546 MiB Jun 17 2019 12:06 /dev/stratis/my-pool/test-fs2
Here as you see the file system uses 546 MB in size.
Persistently mounting a Stratis file system
This procedure persistently mounts a Stratis file system so that it is available automatically after booting the system. get the UUID for the available stratis file systems using lsblk command:
[root@node4 ~]# lsblk --output=UUID /dev/stratis/my-pool/test-fs1 UUID bf11c663-d9da-4bc3-90a8-1440a9184312 [root@node4 ~]# lsblk --output=UUID /dev/stratis/my-pool/test-fs2 UUID 0f6d3423-9dcb-4955-803a-1054c3a65972
As root, edit the /etc/fstab file and add a line for the file system, identified by the UUID. Use xfs as the file system type and add the x-systemd.requires=stratisd.service option.
[root@node4 ~]# vim /etc/fstab UUID=bf11c663-d9da-4bc3-90a8-1440a9184312 /test-fs1 xfs defaults,x-systemd.requires=stratisd.service 0 0 UUID=0f6d3423-9dcb-4955-803a-1054c3a65972 /test-fs2 xfs defaults,x-systemd.requires=stratisd.service 0 0
Next unmount the stratis file system to verify the changes
[root@node4 ~]# umount /test-fs1 [root@node4 ~]# umount /test-fs2/ [root@node4 ~]# df -h | egrep test-fs1|test-fs2
Regenerate mount units so that your system registers the new configuration:
[root@node4 ~]# systemctl daemon-reload
Try mounting the file system to verify that the configuration works:
[root@node4 ~]# mount -a
So all the partitions under our fstab has been successfully mounted including stratis file systems
[root@node4 ~]# df -h | egrep test-fs1|test-fs2 /dev/mapper/stratis-1-a35d85c5802c49b59bb8c81104d43bb4-thin-fs-bf11c663d9da4bc390a81440a9184312 1.0T 7.2G 1017G 1% /test-fs1 /dev/mapper/stratis-1-a35d85c5802c49b59bb8c81104d43bb4-thin-fs-0f6d34239dcb4955803a1054c3a65972 1.0T 7.2G 1017G 1% /test-fs2
Lastly I hope the steps from the article to understand Stratis Architecture, create stratis file system with thin provision, creating pool and mounting the stratis file system to access the data on RHEL 8 Linux was helpful. So, let me know your suggestions and feedback using the comment section.
In the next article I will share the steps to create snapshot, restore file system using snapshot, remove or destroy pools, file systems and other commands on RHEL 8 Linux.
My suggestions: Thank You