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Update "select a storage driver" with current status 

The information on this page was a bit outdated, and
with "overlay" and "devicemapper" being phased-out, could
use some changes;

- de-emphasize "overlay", "devicemapper" and "aufs"
- split "recommended" and "alternative drivers" columns
  (vfs was listed as a "recommended" driver, but definitely
  is not recommended for production use).
- add notes about "overlay" and "devicemapper" being
  deprecated in Docker 18.09
- some other textual changes.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>
This commit is contained in:
Sebastiaan van Stijn 2018-11-12 23:32:52 +01:00
parent f07e2941b4
commit 3b2495966a
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87
storage/storagedriver/select-storage-driver.md
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@ -26,19 +26,27 @@ this decision, there are three high-level factors to consider:
explicitly configured, assuming that the prerequisites for that storage driver
are met:
- If possible, the storage driver with the least amount of configuration is
used, such as `btrfs` or `zfs`. Each of these relies on the backing
filesystem being configured correctly.
- Otherwise, try to use the storage driver with the best overall performance
and stability in the most usual scenarios.
- `overlay2` is preferred, followed by `overlay`. Neither of these requires
extra configuration. `overlay2` is the default choice for Docker CE.
- Try to use the storage driver with the best overall performance and stability
in the most usual scenarios.
- `overlay2` is the preferred storage driver, for all currently supported
Linux distributions, and requires no extra configuration.
- `aufs` is the preferred storage driver for Docker 18.06 and older, when
running on Ubuntu 14.04 on kernel 3.13 (which has no support for `overlay2`.
- `devicemapper` is next, but requires `direct-lvm` for production
environments, because `loopback-lvm`, while zero-configuration, has very
poor performance.
poor performance. `devicemapper` was the recommended storage driver for
CentOS and RHEL, as their kernel version did not support `overlay2`. However,
current versions of CentOS and RHEL now have support for `overlay2`, and
is now the recommended driver.
- The `btrfs` and `zfs` storage drivers are used if they are the backing
filesystem (the filesystem of the host on which Docker is installed).
These filesystems allow for advanced options, such as creating "snapshots",
but require more maintenance and setup. Each of these relies on the backing
filesystem being configured correctly.
- The `vfs` storage driver is intended for testing purposes, and for situations
where no copy-on-write filesystem can be used. Performance of this storage
driver is poor, and not generally recommended for production use.
The selection order is defined in Docker's source code. You can see the order
by looking at
@ -73,25 +81,34 @@ In addition, Docker does not recommend any configuration that requires you to
disable security features of your operating system, such as the need to disable
`selinux` if you use the `overlay` or `overlay2` driver on CentOS.
### Docker EE and CS-Engine
### Docker Engine Enterprise and Docker EE
For Docker EE and CS-Engine, the definitive resource for which storage drivers
are supported is the
For Docker Engine Enterprise and Docker EE, the definitive resource for which
storage drivers are supported is the
[Product compatibility matrix](https://success.docker.com/Policies/Compatibility_Matrix).
To get commercial support from Docker, you must use a supported configuration.
### Docker CE
### Docker Engine Community and Docker CE
For Docker CE, only some configurations are tested, and your operating system's
kernel may not support every storage driver. In general, the following
For Docker Engine Community, only some configurations are tested, and your operating
system's kernel may not support every storage driver. In general, the following
configurations work on recent versions of the Linux distribution:
| Linux distribution | Recommended storage drivers |
|:--------------------|:------------------------------------------------------------------------------------------------------|
| Docker CE on Ubuntu | `aufs`, `devicemapper`, `overlay2` (Ubuntu 14.04.4 or later, 16.04 or later), `overlay`, `zfs`, `vfs` |
| Docker CE on Debian | `aufs`, `devicemapper`, `overlay2` (Debian Stretch), `overlay`, `vfs` |
| Docker CE on CentOS | `devicemapper`, `vfs` |
| Docker CE on Fedora | `devicemapper`, `overlay2` (Fedora 26 or later, experimental), `overlay` (experimental), `vfs` |
| Linux distribution | Recommended storage drivers | Alternative drivers |
|:--------------------|:-----------------------------------------------------------------------|:--------------------------------------------------|
| Docker CE on Ubuntu | `overlay2` or `aufs` (for Ubuntu 14.04 running on kernel 3.13) | `overlay`¹, `devicemapper`², `zfs`, `vfs` |
| Docker CE on Debian | `overlay2` (Debian Stretch), `aufs` or `devicemapper` (older versions) | `overlay`¹, `vfs` |
| Docker CE on CentOS | `overlay2` | `overlay`¹, `devicemapper`², `zfs`, `vfs` |
| Docker CE on Fedora | `overlay2` | `overlay`¹, `devicemapper`², `zfs`, `vfs` |
¹) The `overlay` storage driver is marked deprecated in docker 18.09, and will be
removed in a future release. Users of the `overlay` storage driver are recommended
to migrate to `overlay2`.
²) The `devicemapper` storage driver is marked deprecated in docker 18.09, and will be
removed in a future release. Users of the `devicemapper` storage driver are recommended
to migrate to `overlay2`.
When possible, `overlay2` is the recommended storage driver. When installing
Docker for the first time, `overlay2` is used by default. Previously, `aufs` was
@ -140,12 +157,12 @@ backing filesystems.
| Storage driver | Supported backing filesystems |
|:----------------------|:------------------------------|
| `overlay`, `overlay2` | `ext4`, `xfs` |
| `aufs` | `ext4`, `xfs` |
| `overlay2`, `overlay` | `xfs` with fstype=1, `ext4` |
| `aufs` | `xfs`, `ext4` |
| `devicemapper` | `direct-lvm` |
| `btrfs` | `btrfs` |
| `zfs` | `zfs` |
| `vfs` | any filesystem |
## Other considerations
@ -155,13 +172,14 @@ Among other things, each storage driver has its own performance characteristics
that make it more or less suitable for different workloads. Consider the
following generalizations:
- `aufs`, `overlay`, and `overlay2` all operate at the file level rather than
- `overlay2`, `aufs`, and `overlay` all operate at the file level rather than
the block level. This uses memory more efficiently, but the container's
writable layer may grow quite large in write-heavy workloads.
- Block-level storage drivers such as `devicemapper`, `btrfs`, and `zfs` perform
better for write-heavy workloads (though not as well as Docker volumes).
- For lots of small writes or containers with many layers or deep filesystems,
`overlay` may perform better than `overlay2`.
`overlay` may perform better than `overlay2`, but consumes more inodes, which
can lead to inode exhaustion.
- `btrfs` and `zfs` require a lot of memory.
- `zfs` is a good choice for high-density workloads such as PaaS.
@ -186,15 +204,8 @@ specific shared storage system.
For some users, stability is more important than performance. Though Docker
considers all of the storage drivers mentioned here to be stable, some are newer
and are still under active development. In general, `aufs`, `overlay`, and
`devicemapper` are the choices with the highest stability.
### Experience and expertise
Choose a storage driver that your organization is comfortable maintaining. For
example, if you use RHEL or one of its downstream forks, you may already have
experience with LVM and Device Mapper. If so, the `devicemapper` driver might
be the best choice.
and are still under active development. In general, `overlay2`, `aufs`, `overlay`,
and `devicemapper` are the choices with the highest stability.
### Test with your own workloads
@ -216,8 +227,8 @@ $ docker info
Containers: 0
Images: 0
Storage Driver: overlay
Backing Filesystem: extfs
Storage Driver: overlay2
Backing Filesystem: xfs
<output truncated>
```