Quick Start: ublk

Initialize the disk file with an empty ext4:

touch ublk.raw
truncate --size 1G ublk.raw
mkfs.ext4 ublk.raw

Create the config file ublk-config.yaml:

path: "ublk.raw"

Start the backend:

export RUST_LOG=debug
sudo -E ~/projects/ubiblk/target/debug/ublk-backend --config ublk-config.yaml

You should see something like:

[INFO  ubiblk::backends::common] Starting ublk backend. Process ID: 3327618
[INFO  ubiblk::backends::ublk] Creating ublk backend ...
[INFO  libublk::ctrl] ctrl: device 4 flags 2 created
[INFO  libublk::io] dev 4 initialized
[INFO  libublk::io] dev 4 queue 0 started
[INFO  ubiblk::backends::ublk] ublk device is available at /dev/ublkb4

Now you can use /dev/ublkb4.

$ sudo fsck.ext4 /dev/ublkb4
e2fsck 1.46.5 (30-Dec-2021)
/dev/ublkb4: clean, 11/65536 files, 12955/262144 blocks

$ mkdir mnt
$ sudo mount /dev/ublkb4 mnt

Checking ublk support

To check if your kernel supports ublk, run:

grep CONFIG_BLK_DEV_UBLK  /boot/config-$(uname -r)

If the output is CONFIG_BLK_DEV_UBLK=y, then ublk support is built into the kernel. If it is CONFIG_BLK_DEV_UBLK=m, then ublk is built as a module and you need to load it with:

sudo modprobe ublk_drv

fio results

Sync implementation:

• 4k rand read: 57.8MiB/s
• 4k rand write: 153MiB/s

Async implementation:

• 4k rand read: 445MiB/s
• 4k rand write: 591MiB/s