Fix thin pool devicemapper docs overwritten
Signed-off-by: Matt Bentley <matt.bentley@docker.com>
(cherry picked from commit 79205c3f06)
Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
This commit is contained in:
Matt Bentley
Sebastiaan van Stijn
parent
fa29ecbceb
commit
3bdc7244a8
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@ -212,7 +212,7 @@ a `direct-lvm` configuration.
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> and have images you want to keep, `push` them Docker Hub or your private
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> Docker Trusted Registry before attempting this procedure.
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The procedure below will create a 90GB data volume and 4GB metadata volume to
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The procedure below will create a logical volume configured as a thin pool to
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use as backing for the storage pool. It assumes that you have a spare block
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device at `/dev/xvdf` with enough free space to complete the task. The device
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identifier and volume sizes may be be different in your environment and you
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@ -221,106 +221,146 @@ assumes that the Docker daemon is in the `stopped` state.
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1. Log in to the Docker host you want to configure and stop the Docker daemon.
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2. If it exists, delete your existing image store by removing the
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`/var/lib/docker` directory.
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2. Install the LVM2 package.
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The LVM2 package includes the userspace toolset that provides logical volume
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management facilities on linux.
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3. Create a physical volume replacing `/dev/xvdf` with your block device.
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```bash
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$ sudo rm -rf /var/lib/docker
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$ pvcreate /dev/xvdf
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```
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3. Create an LVM physical volume (PV) on your spare block device using the
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`pvcreate` command.
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4. Create a 'docker' volume group.
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```bash
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$ sudo pvcreate /dev/xvdf
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Physical volume `/dev/xvdf` successfully created
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$ vgcreate docker /dev/xvdf
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```
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The device identifier may be different on your system. Remember to substitute
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your value in the command above. If your host is running on AWS EC2, you may
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need to install `lvm2` and <a href="http://goo.gl/Q5pUwG"
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target="_blank">attach an EBS device</a> to use this procedure.
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5. Create a thin pool named `thinpool`.
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4. Create a new volume group (VG) called `vg-docker` using the PV created in
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the previous step.
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In this example, the data logical is 95% of the 'docker' volume group size.
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Leaving this free space allows for auto expanding of either the data or
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metadata if space runs low as a temporary stopgap.
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```bash
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$ sudo vgcreate vg-docker /dev/xvdf
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Volume group `vg-docker` successfully created
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$ lvcreate --wipesignatures y -n thinpool docker -l 95%VG
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$ lvcreate --wipesignatures y -n thinpoolmeta docker -l 1%VG
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```
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5. Create a new 90GB logical volume (LV) called `data` from space in the
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`vg-docker` volume group.
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6. Convert the pool to a thin pool.
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```bash
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$ sudo lvcreate -L 90G -n data vg-docker
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Logical volume `data` created.
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$ lvconvert -y --zero n -c 512K --thinpool docker/thinpool --poolmetadata docker/thinpoolmeta
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```
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The command creates an LVM logical volume called `data` and an associated
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block device file at `/dev/vg-docker/data`. In a later step, you instruct the
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`devicemapper` storage driver to use this block device to store image and
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container data.
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If you receive a signature detection warning, make sure you are working on
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the correct devices before continuing. Signature warnings indicate that the
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device you're working on is currently in use by LVM or has been used by LVM in
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the past.
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6. Create a new logical volume (LV) called `metadata` from space in the
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`vg-docker` volume group.
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7. Configure autoextension of thin pools via an `lvm` profile.
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```bash
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$ sudo lvcreate -L 4G -n metadata vg-docker
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Logical volume `metadata` created.
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$ vi /etc/lvm/profile/docker-thinpool.profile
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```
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This creates an LVM logical volume called `metadata` and an associated
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block device file at `/dev/vg-docker/metadata`. In the next step you instruct
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the `devicemapper` storage driver to use this block device to store image and
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container metadata.
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8. Specify 'thin_pool_autoextend_threshold' value.
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7. Start the Docker daemon with the `devicemapper` storage driver and the
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`--storage-opt` flags.
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The value should be the percentage of space used before `lvm` attempts
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to autoextend the available space (100 = disabled).
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The `data` and `metadata` devices that you pass to the `--storage-opt`
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options were created in the previous steps.
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```
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thin_pool_autoextend_threshold = 80
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```
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9. Modify the `thin_pool_autoextend_percent` for when thin pool autoextension occurs.
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The value's setting is the perentage of space to increase the thin pool (100 =
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disabled)
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```
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thin_pool_autoextend_percent = 20
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```
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10. Check your work, your `docker-thinpool.profile` file should appear similar to the following:
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An example `/etc/lvm/profile/docker-thinpool.profile` file:
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```
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activation {
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thin_pool_autoextend_threshold=80
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thin_pool_autoextend_percent=20
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}
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```
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11. Apply your new lvm profile
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```bash
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$ sudo docker daemon --storage-driver=devicemapper --storage-opt dm.datadev=/dev/vg-docker/data --storage-opt dm.metadatadev=/dev/vg-docker/metadata &
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[1] 2163
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[root@ip-10-0-0-75 centos]# INFO[0000] Listening for HTTP on unix (/var/run/docker.sock)
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INFO[0027] Option DefaultDriver: bridge
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INFO[0027] Option DefaultNetwork: bridge
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<-- output truncated -->
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INFO[0027] Daemon has completed initialization
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INFO[0027] Docker daemon commit=1b09a95 graphdriver=aufs version=1.11.0-dev
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$ lvchange --metadataprofile docker-thinpool docker/thinpool
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```
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It is also possible to set the `--storage-driver` and `--storage-opt` flags
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in the Docker config file and start the daemon normally using the `service` or
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`systemd` commands.
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8. Use the `docker info` command to verify that the daemon is using `data` and
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`metadata` devices you created.
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12. Verify the `lv` is monitored.
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```bash
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$ sudo docker info
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INFO[0180] GET /v1.20/info
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Containers: 0
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Images: 0
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Storage Driver: devicemapper
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Pool Name: docker-202:1-1032-pool
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Pool Blocksize: 65.54 kB
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Backing Filesystem: xfs
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Data file: /dev/vg-docker/data
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Metadata file: /dev/vg-docker/metadata
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[...]
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$ lvs -o+seg_monitor
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```
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The output of the command above shows the storage driver as `devicemapper`.
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The last two lines also confirm that the correct devices are being used for
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the `Data file` and the `Metadata file`.
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13. If the Docker daemon was previously started, clear your graph driver directory.
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Clearing your graph driver removes any images, containers, and volumes in your
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Docker installation.
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```bash
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$ rm -rf /var/lib/docker/*
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```
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14. Configure the Docker daemon with specific devicemapper options.
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There are two ways to do this. You can set options on the commmand line if you start the daemon there:
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```bash
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--storage-driver=devicemapper --storage-opt=dm.thinpooldev=/dev/mapper/docker-thinpool --storage-opt dm.use_deferred_removal=true
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```
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You can also set them for startup in the `daemon.json` configuration, for example:
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```json
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{
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"storage-driver": "devicemapper",
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"storage-opts": [
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"dm.thinpooldev=/dev/mapper/docker-thinpool",
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"dm.use_deferred_removal=true"
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]
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}
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```
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15. If using systemd and modifying the daemon configuration via unit or drop-in file, reload systemd to scan for changes.
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```bash
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$ systemctl daemon-reload
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```
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16. Start the Docker daemon.
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```bash
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$ systemctl start docker
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```
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After you start the Docker daemon, ensure you monitor your thin pool and volume
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group free space. While the volume group will auto-extend, it can still fill
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up. To monitor logical volumes, use `lvs` without options or `lvs -a` to see tha
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data and metadata sizes. To monitor volume group free space, use the `vgs` command.
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Logs can show the auto-extension of the thin pool when it hits the threshold, to
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view the logs use:
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```bash
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$ journalctl -fu dm-event.service
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```
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If you run into repeated problems with thin pool, you can use the
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`dm.min_free_space` option to tune the Engine behavior. This value ensures that
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operations fail with a warning when the free space is at or near the minimum.
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For information, see <a
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href="../../../reference/commandline/daemon/#storage-driver-options"
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target="_blank">the storage driver options in the Engine daemon reference</a>.
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### Examine devicemapper structures on the host
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@ -329,20 +369,20 @@ You can use the `lsblk` command to see the device files created above and the
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```bash
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$ sudo lsblk
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NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
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xvda 202:0 0 8G 0 disk
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└─xvda1 202:1 0 8G 0 part /
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xvdf 202:80 0 10G 0 disk
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├─vg--docker-data 253:0 0 90G 0 lvm
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│ └─docker-202:1-1032-pool 253:2 0 10G 0 dm
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└─vg--docker-metadata 253:1 0 4G 0 lvm
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└─docker-202:1-1032-pool 253:2 0 10G 0 dm
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NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
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xvda 202:0 0 8G 0 disk
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└─xvda1 202:1 0 8G 0 part /
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xvdf 202:80 0 10G 0 disk
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├─vg--docker-data 253:0 0 90G 0 lvm
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│ └─docker-202:1-1032-pool 253:2 0 10G 0 dm
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└─vg--docker-metadata 253:1 0 4G 0 lvm
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└─docker-202:1-1032-pool 253:2 0 10G 0 dm
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```
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The diagram below shows the image from prior examples updated with the detail
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from the `lsblk` command above.
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In the diagram, the pool is named `Docker-202:1-1032-pool` and spans the `data`
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and `metadata` devices created earlier. The `devicemapper` constructs the pool
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@ -427,12 +467,10 @@ The `Data Space` values show that the pool is 100GB total. This example extends
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3. Verify the file size changed.
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```bash
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$ sudo ls -al /var/lib/docker/devicemapper/devicemapper/
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total 1175492
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drwx------ 2 root root 4096 Mar 29 02:45 .
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drwx------ 5 root root 4096 Mar 29 02:48 ..
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-rw------- 1 root root 214748364800 Mar 31 11:20 data
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-rw------- 1 root root 2147483648 Mar 31 11:17 metadata
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$ sudo ls -lh /var/lib/docker/devicemapper/devicemapper/
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total 1.2G
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-rw------- 1 root root 200G Apr 14 08:47 data
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-rw------- 1 root root 2.0G Apr 19 13:27 metadata
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```
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4. Reload data loop device
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@ -450,13 +488,14 @@ The `Data Space` values show that the pool is 100GB total. This example extends
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a. Get the pool name first.
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```bash
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$ sudo dmsetup status docker-8:1-123141-pool: 0 209715200 thin-pool 91
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$ sudo dmsetup status | grep pool
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docker-8:1-123141-pool: 0 209715200 thin-pool 91
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422/524288 18338/1638400 - rw discard_passdown queue_if_no_space -
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```
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The name is the string before the colon.
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b. Dump the device mapper table first.
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b. Dump the device mapper table first.
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```bash
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$ sudo dmsetup table docker-8:1-123141-pool
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@ -469,6 +508,7 @@ The `Data Space` values show that the pool is 100GB total. This example extends
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reflect the new number of 512 byte sectors in the disk. For example, as the
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new loop size is 200GB, change the second number to 419430400.
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d. Reload the thin pool with the new sector number
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```bash
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@ -533,7 +573,7 @@ disk partition.
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c. Calculate the real total sectors of the thin pool now. we can use `blockdev` to get the real size of data lv.
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Change the second number of the table info (i.e. the disk end sector) to
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Change the second number of the table info (i.e. the number of sectors) to
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reflect the new number of 512 byte sectors in the disk. For example, as the
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new data `lv` size is `264132100096` bytes, change the second number to
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`515883008`.
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@ -592,8 +632,8 @@ There are several other things that impact the performance of the
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- **The mode.** The default mode for Docker running the `devicemapper` storage
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driver is `loop-lvm`. This mode uses sparse files and suffers from poor
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performance. It is **not recommended for production**. The recommended mode
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for production environments is `direct-lvm` where the storage driver writes
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performance. It is **not recommended for production**. The recommended mode for
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production environments is `direct-lvm` where the storage driver writes
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directly to raw block devices.
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- **High speed storage.** For best performance you should place the `Data file`
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@ -601,10 +641,10 @@ There are several other things that impact the performance of the
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attached storage or from a SAN or NAS array.
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- **Memory usage.** `devicemapper` is not the most memory efficient Docker
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storage driver. Launching *n* copies of the same container loads *n* copies
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of its files into memory. This can have a memory impact on your Docker host.
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As a result, the `devicemapper` storage driver may not be the best choice for
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PaaS and other high density use cases.
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storage driver. Launching *n* copies of the same container loads *n* copies of
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its files into memory. This can have a memory impact on your Docker host. As a
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result, the `devicemapper` storage driver may not be the best choice for PaaS
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and other high density use cases.
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One final point, data volumes provide the best and most predictable
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performance. This is because they bypass the storage driver and do not incur
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