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
Add mount point to /etc/fstab using file system UUID
You can use /dev/stratis/<pool name>/<file system name> but each time you rename a pool or file system you will need to update /etc/fstab, thus using file system UUID is recommended.
# blkid -p /dev/stratis/stratis_howto/fs_howto
/dev/stratis/stratis_howto/fs_howto: UUID="a38780e5-04e3-49da-8b95-2575d77e947c" TYPE="xfs" USAGE="filesystem"
# echo "UUID=a38780e5-04e3-49da-8b95-2575d77e947c /mnt xfs defaults 0 0" >> /etc/fstab
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