Stratis how-to/walk-through
2018-11-27Contents
Introduction
Stratis provides ZFS/Btrfs-style features by integrating layers of existing technology: Linux’s devicemapper subsystem, and the XFS filesystem. The stratisd daemon manages collections of block devices, and provides a D-Bus API. The stratis-cli provides a command-line tool stratis which itself uses the D-Bus API to communicate with stratisd.
Installation
# dnf install stratisd stratis-cli
Starting the service
# systemctl start stratisd
# systemctl enable stratisd
Created symlink /etc/systemd/system/sysinit.target.wants/stratisd.service →
/usr/lib/systemd/system/stratisd.service.
Locate an empty block device
Use utilities like lsblk and blkid to find a block device to use with Stratis.
# lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sda 8:0 0 28G 0 disk
├─sda1 8:1 0 1G 0 part /boot
├─sda2 8:2 0 2.8G 0 part [SWAP]
└─sda3 8:3 0 15G 0 part /
sdb 8:16 0 1T 0 disk
sdc 8:32 0 2T 0 disk
sdd 8:48 0 8G 0 disk
sde 8:64 0 8G 0 disk
sdf 8:80 0 8G 0 disk
sdg 8:96 0 8G 0 disk
sr0 11:0 1 1024M 0 rom
# blkid -p /dev/sda
/dev/sda: PTUUID="b7168b63" PTTYPE="dos"
Not empty, it contains a partition table.
# blkid -p /dev/sdb
Empty, no known signatures found.
If you are positive that you have a block device that you want to use and it has a signature on it, you need to clear the signature before using it in a Stratis pool. Otherwise you will get an error when you attempt to create the pool.
To clear a device so that it can be used by Stratis.
# blkid -p /dev/sdc
/dev/sdc: UUID="770587cc-cfd3-44cb-82e2-756902cf458b" VERSION="1.0" TYPE="ext4" USAGE="filesystem"
# wipefs -a /dev/sdc
/dev/sdc: 2 bytes were erased at offset 0x00000438 (ext4): 53 ef
Creating a pool
A pool with one block device.
# stratis pool create stratis_howto /dev/sdb
# stratis pool list
Name Total Physical Size Total Physical Used
stratis_howto 1 TiB 52 MiB
A pool with 2 block devices.
# stratis pool create tale_of_2_disks /dev/sdd /dev/sdf
# stratis pool list
Name Total Physical Size Total Physical Used
stratis_howto 1 TiB 52 MiB
tale_of_2_disks 16 GiB 56 MiB
Creating a filesystem from the pool
# stratis filesystem create stratis_howto fs_howto
# stratis filesystem list
Pool Name Name Used Created Device
stratis_howto fs_howto 546 MiB Nov 09 2018 11:08 /dev/stratis/stratis_howto/fs_howto
To create another file system, just repeat the same command with a different file system name. The file system names are required to be unique in a pool.
# stratis filesystem create stratis_howto my_precious
# stratis filesystem list
Pool Name Name Used Created Device
stratis_howto fs_howto 546 MiB Nov 09 2018 11:08 /dev/stratis/stratis_howto/fs_howto
stratis_howto my_precious 546 MiB Nov 09 2018 11:09 /dev/stratis/stratis_howto/my_precious
The file system is created on a thinly provisioned 1 TB block device. Stratis will take care of allocating blocks from the pool and re-sizing the XFS file system as needed during its lifetime.
You can also constrain the file system list output by including the pool name.
# stratis pool create olympic /dev/sdc
# stratis filesystem create olympic backstroke
# stratis filesystem
Pool Name Name Used Created Device
olympic backstroke 546 MiB Nov 09 2018 11:10 /dev/stratis/olympic/backstroke
stratis_howto fs_howto 546 MiB Nov 09 2018 11:08 /dev/stratis/stratis_howto/fs_howto
stratis_howto my_precious 546 MiB Nov 09 2018 11:09 /dev/stratis/stratis_howto/my_precious
# stratis filesystem list stratis_howto
Pool Name Name Used Created Device
stratis_howto fs_howto 546 MiB Nov 09 2018 11:08 /dev/stratis/stratis_howto/fs_howto
stratis_howto my_precious 546 MiB Nov 09 2018 11:09 /dev/stratis/stratis_howto/my_precious
Mount the file system
# mount /dev/stratis/stratis_howto/fs_howto /mnt
Modifying /etc/fstab so that your filesystem is mounted at boot
If you insert the following line in your /etc/fstab file, your pool will be started and your filesystem will be mounted during the boot process.
/dev/stratis/<pool name>/<file system name> /mnt xfs defaults,x-systemd.requires=stratis-fstab-setup@<pool uuid>.service,x-systemd.after=stratis-fstab-setup@<pool uuid>.service 0 2
This will ensure that the filesystem's pool is started. In case the pool is encrypted stratisd will attempt to unlock the pool. If the pool can not be unlocked without user intervention, the user will be be prompted for a passphrase at boot.
Other useful pool operations
add-data: Add a disk to an existing pool
# stratis pool add-data tale_of_2_disks /dev/sdc
# stratis pool list
Name Total Physical Size Total Physical Used
stratis_howto 1 TiB 52 MiB
tale_of_2_disks 2.02 TiB 60 MiB
rename: Rename a pool
# stratis pool rename tale_of_2_disks 3_amigos
# stratis pool list
Name Total Physical Size Total Physical Used
3_amigos 2.02 TiB 60 MiB
stratis_howto 1 TiB 52 MiB
init-cache: Initialize cache and add block device as cache device (typically something like SSD)
# stratis pool init-cache 3_amigos /dev/sde
add-cache: Add a block device as cache to a pool with an existing cache
# stratis pool add-cache 3_amigos /dev/sdg
destroy: Destroy a pool, no file systems can exist in pool
# stratis pool destroy 3_amigos
# stratis pool list
Name Total Physical Size Total Physical Used
stratis_howto 1 TiB 52 MiB
Other useful file system operations
destroy: Remove a Stratis provided filesystem
To remove a Stratis provided filesystem, make sure that it’s not in use, and then destroy it.
# stratis filesystem list
Pool Name Name Used Created Device
olympic backstroke 546 MiB Nov 09 2018 11:10 /dev/stratis/olympic/backstroke
stratis_howto fs_howto 546 MiB Nov 09 2018 11:08 /dev/stratis/stratis_howto/fs_howto
stratis_howto my_precious 546 MiB Nov 09 2018 11:09 /dev/stratis/stratis_howto/my_precious
# stratis filesystem destroy stratis_howto my_precious
# stratis filesystem list
Pool Name Name Used Created Device
olympic backstroke 546 MiB Nov 09 2018 11:10 /dev/stratis/olympic/backstroke
stratis_howto fs_howto 546 MiB Nov 09 2018 11:08 /dev/stratis/stratis_howto/fs_howto
rename: Rename a file system
# stratis filesystem rename olympic backstroke some_fs
snapshot: Create a snapshot
To create a snapshot, which is a read/writeable thinly provisioned point in time copy of the source FS.
# stratis filesystem snapshot olympic some_fs some_fs_snapshot
# stratis filesystem list olympic
Pool Name Name Used Created Device
olympic some_fs 546 MiB Nov 09 2018 11:10 /dev/stratis/olympic/some_fs
olympic some_fs_snapshot 546 MiB Nov 09 2018 11:26 /dev/stratis/olympic/some_fs_snapshot
Misc. operations
Query which block devices belong to a pool or all of Stratis.
# stratis blockdev list olympic
Pool Name Device Node Physical Size State Tier
olympic /dev/sdc 2.00 TiB In-use Data
# stratis blockdev list
Pool Name Device Node Physical Size State Tier
olympic /dev/sdc 2.00 TiB In-use Data
stratis_howto /dev/sdb 1 TiB In-use Data
Query the Stratis daemon (stratisd) version.
# stratis daemon version
1.0.1