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Stratis is considered Technology Preview and is not intended for production use. For information on Red Hat scope of support for Technology Preview features, see: Technology Preview Features Support Scope |
Stratis is a command-line tool to create, modify, and destroy Stratis pools, and the filesystems allocated from the pool. Stratis creates a pool from one or more block devices (blockdevs), and then enables multiple filesystems to be created from the pool.
Instead of an entirely in-kernel approach like ZFS or Btrfs, Stratis uses a hybrid user/kernel approach that builds upon existing block capabilities like device-mapper, existing filesystem capabilities like XFS, and a user space daemon for monitoring and control.
For these exercises, you will be using the host node2 as user root.
From host bastion, ssh to node2.
ssh node2Use sudo to elevate your priviledges.
sudo -iVerify that you are on the right host for these exercises.
workshop-stratis-checkhost.shYou are now ready to proceed with these exercises.
Install the required packages - this will pull in several Python related dependencies.
yum install -y stratisd stratis-cliNext we need to enable the stratisd service
systemctl enable --now stratisd|
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The "enable --now" syntax is new in RHEL 8. It allows for permanently enabling as well as immediately starting services in a single command. |
Finally check the service status.
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: enabled)
Active: active (running) since Sat 2019-04-27 18:41:52 EDT; 10s ago
Docs: man:stratisd(8)
Main PID: 9562 (stratisd)
Tasks: 1 (limit: 24006)
Memory: 940.0K
CGroup: /system.slice/stratisd.service
└─9562 /usr/libexec/stratisd --debug
Apr 27 18:41:52 node2.example.com systemd[1]: Started A daemon that manages a pool of block devices to create flexible file systems.
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/dev/sda is the system disk, DO NOT use it in any of the stratis commands or the vm will become unusable. |
Since we will be reusing the same resources for many exercises, we will begin by wiping everything clean. Don’t worry if you get an error message.
umount /mnt/lab*umount /summitdirvgremove -ff vg_labpvremove /dev/sd{b..e}wipefs -a /dev/sd{b..e}partprobeSee what disks/block devices are present. Remeber that /dev/sda is used by the operating system and should NOT be specified for any of these exercises.
sfdisk -s{disk0}: 31457280
{disk1}: 5242880
{disk2}: 5242880
{disk3}: 5242880
{disk4}: 5242880
total: 52428800 blocks
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REMEMBER - DON’T USE /dev/sda!!! |
Create a storage pool using a pair of the available disks.
stratis pool create summitpool /dev/sdb /dev/sdcVerify your work and confirm the existence of the new storage pool with the combined available capacity.
stratis pool listName Total Physical Size Total Physical Used summitpool 10 GiB 56 MiB
Check the status of the block devices
stratis blockdev listPool Name Device Node Physical Size State Tier
summitpool {disk1} 5 GiB In-use Data
summitpool {disk2} 5 GiB In-use Data
Now create a filesystem, a directory mount point, and mount the filesystem: (note that “fs” can optionally be written out as “filesystem”)
stratis fs create summitpool summitfsstratis fs list[bash,options="nowrap"] Pool Name Name Used Created Device UUID summitpool summitfs 546 MiB Apr 18 2020 09:15 /dev/stratis/summitpool/summitfs 095fb4891a5743d0a589217071ff71dc
mkdir /summitdirmount /dev/stratis/summitpool/summitfs /summitdirdf -hFilesystem 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 17M 1.9G 1% /run tmpfs 1.9G 0 1.9G 0% /sys/fs/cgroup /dev/vda1 30G 2.4G 28G 8% / tmpfs 379M 0 379M 0% /run/user/1000 /dev/mapper/stratis-1-3e8e[_truncated_]71dc 1.0T 7.2G 1017G 1% /summitdir
The actual space used by a filesystem can be shown using the stratis fs list command as shown above. Notice how the summitdir filesystem has a virtual size of 1T. If the data in a filesystem actually approaches its virtual size, Stratis will automatically grow the filesystem.
Now make sure the filesystem will mount at boot time by adjusting the systems fstab. You’ve been provided a simple script to perform this edit, but the maunal steps are also outlined below in the 'Native command(s)' note.
workshop-stratis-fstab.sh|
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Native command(s) to amend /etc/fstab UUID=`lsblk -n -o uuid /dev/stratis/summitpool/summitfs`
echo "UUID=${UUID} /summitdir xfs defaults 0 0" >> /etc/fstab
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Verify that the /etc/fstab entry is correct by unmounting and mounting the filesystem one last time.
umount /summitdirmount /summitdirdf -hFilesystem 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 17M 1.9G 1% /run tmpfs 1.9G 0 1.9G 0% /sys/fs/cgroup /dev/vda1 30G 2.4G 28G 8% / tmpfs 379M 0 379M 0% /run/user/1000 /dev/mapper/stratis-1-3e8e[_truncated_]71dc 1.0T 7.2G 1017G 1% /summitdir
Finally, Stratis also makes it easy to add space to a pool. Suppose the “summitfs” filesystem is growing close to the physical space in “summitpool”, adding an additional disk/block device is done using:
stratis pool add-data summitpool /dev/sdestratis blockdevPool Name Device Node Physical Size State Tier
summitpool {disk1} 5 GiB In-use Data
summitpool {disk2} 5 GiB In-use Data
summitpool {disk3} 5 GiB In-use Cache
summitpool {disk4} 5 GiB In-use Data
Verify that the pool shows the additional space, and that the amount used is now in a safe range.
stratis poolName Total Physical Size Total Physical Used summitpool 15 GiB 606 MiB
Stratis also makes it easy to add cache devices. For example, say the filesystem we just created runs into some I/O performance issues. You bought an SSD (solid state disk) and need to configure it into the system to act as a high speed cache. Use the following commands to add the drive (/dev/vdd) and check its status:
stratis pool init-cache summitpool /dev/sddstratis blockdevPool Name Device Node Physical Size State Tier
summitpool {disk1} 5 GiB In-use Data
summitpool {disk2} 5 GiB In-use Data
summitpool {disk3} 5 GiB In-use Cache
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