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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.
Starting on the host workstation.example.com, let’s ssh over to node2.example.com. No password should be required.
ssh node2.example.com
Verify that you are on the right host for these exercises.
cheat-stratis-checkhost.sh
You are now ready to begin your exercises.
Install the required packages - this will pull in several Python related dependencies.
yum install -y stratisd stratis-cli
Next 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
Your output should look like this. (You can press "q" or CTRL+C to exit the status output)
● 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/vda is the system disk, DO NOT use it in any of the stratis commands or the vm will become unusable. |
Next, see what disks/block devices are present, create a pool, create a filesystem in the pool, and mount the filesystem.
sfdisk -s
/dev/vda: 10485760 // (1)
/dev/vdb: 5242880
/dev/vdc: 5242880
/dev/mapper/rhel-root: 8384512
/dev/mapper/rhel-swap: 1048576
/dev/sdd: 5242880
/dev/sdc: 5242880
/dev/sda: 5242880
/dev/sdb: 5242880
total: 51376128 blocks-
REMEMBER - DON’T USE VDA!!!
stratis pool create summitpool /dev/vdb /dev/vdc
stratis pool list
Name Total Physical Size Total Physical Used
summitpool 10 GiB 56 MiBCheck the status of the block devices
stratis blockdev list
Pool Name Device Node Physical Size State Tier
summitpool /dev/vdb 5 GiB In-use Data
summitpool /dev/vdc 5 GiB In-use DataNow 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 summitfs
stratis fs
Pool Name Name Used Device UUID
summitpool summitfs 546 MiB /stratis/summitpool/summitfs 9d92786138bb4fd6867c45610dcebd1fmkdir /summitdir mount /stratis/summitpool/summitfs /summitdir 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 8.0G 1.3G 6.8G 16% /
/dev/vda1 1014M 163M 852M 17% /boot
tmpfs 379M 0 379M 0% /run/user/1000
/dev/mapper/stratis-1f68[truncated]ed1f 1.0T 7.2G 1017G 1% /summitdirNow make sure the filesystem will mount at boot time by adding the following line to the end of the /etc/fstab file:
UUID=<the-uuid-unique-to-the-new-filesystem> /summitdir xfs defaults 0 0
If you are comfortable with an editor, you can type it in or cut and paste using the UUID from the output of “stratis fs”. If not, you can use a cheat-script we prepared for you.
UUID=<the-uuid-unique-to-the-new-filesystem> /summitdir xfs defaults 0 0cheat-stratis-fstab.sh
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Native command(s) to amend /etc/fstab UUID=`lsblk -n -o uuid /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 filesytem one last time.
umount /summitdir mount /summitdir df -h
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/sda) and check its status:
stratis pool add-cache summitpool /dev/sda
stratis blockdev
Pool Name Device Node Physical Size State Tier
summitpool /dev/sda 5 GiB In-use Cache
summitpool /dev/vdb 5 GiB In-use Data
summitpool /dev/vdc 5 GiB In-use DataFinally, 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/sdb
stratis blockdev
Pool Name Device Node Physical Size State Tier
summitpool /dev/sda 5 GiB In-use Cache
summitpool /dev/sdb 5 GiB In-use Data
summitpool /dev/vdb 5 GiB In-use Data
summitpool /dev/vdc 5 GiB In-use DataVerify that the pool shows the additional space, and that the amount used is now in a safe range.
stratis pool
Name Total Physical Size Total Physical Used
summitpool 15 GiB 606 MiB