Docker is an open-source containerization platform. It enables developers to package applications into containers—standardized executable components combining application source code with the operating system (OS) libraries and dependencies required to run that code in any environment. Containers simplify the delivery of distributed applications and have become increasingly popular as organizations shift to cloud-native development and hybrid multi-cloud environments.

Developers can create containers without Docker, but the platform makes it easier, simpler, and safer to build, deploy and manage containers. Docker is essentially a toolkit that enables developers to build, deploy, run, update, and stop containers using simple commands and work-saving automation through a single API.

It used to be that when you wanted to run a web application, you bought a server, installed Linux, set up a LAMP stack, and ran the app. If your app got popular, you practiced good load balancing by setting up a second server to ensure the application wouldn't crash from too much traffic.

Docker storage motive force also referred to as graph driver affords a mechanism to shop and manage images and containers on the Docker host. Docker uses a pluggable architecture that helps one-of-a-kind storage drivers. Garage drivers allow our workloads to be put in writing to the container’s writable layer. There are several one-of-a-kind storage drivers supported through docker, we want to pick the excellent storage driver for our workloads. To choose the nice garage driving force, it is crucial to apprehend the procedure of building and storing images in docker and how those images are utilized by bins. The default garage driver is overlay2 and it's far supported on docker engine – community, and docker ee 17.06.02-ee5 and up, but, we can exchange it as in step with our requirement.

Below are different storage drivers supported by Docker: –

It is the default storage driver currently.

It is supported by Docker Engine – Community, and Docker EE 17.06.02-ee5, and a newer version.

It is newer and more stable than its original driver called ‘overlay’.

The backing filesystem for overlay2 and overlay driver is off.

It is supported by Linux kernel version 4.0 or higher, version 3.10.0-514 or higher of RHEL or CentOS is required for overlay2 otherwise we need to use an overlay storage driver that is not recommended.

Overlay2 and overlay drivers come under Linux kernel driver OverlayFS storage driver which is a modern union filesystem and it is similar to aufs, however, OverlayFs is faster and easy to implement.

AUFS is a union filesystem, which means it presents multiple directories called branches in AUFS as a single directory on a single Linux host. These directories are known as layers in Docker.

It was the default storage driver before overlay2 was used to manage images and layers on Docker for Ubuntu, and Debian versions before Stretch. It was the default storage driver in Ubuntu 14.04 and earlier.

This driver is good for Platform as a Service where container density is important because AUFS can share the images between multiple running containers efficiently.

It provides a fast container startup and uses less disk space as AUFS shares images between multiple running containers.

It uses memory efficiently, however, not efficient in write-heavy workloads as latencies are high while writing to the container because it has multiple directories so the file needs to be located and copied to the container's top writable layer.

It should be used with Solid State Drives for faster read and write than spinning disk and use volumes for write-heavy workloads to get better performance.

The backing filesystem for AUFS is xfs and ext4 Linux file system.

It is a block storage driver that stores data in blocks.

It is good for write-heavy workloads as it stores data at the block level instead of the file level.

It is a kernel-based framework and Docker’s device-mapper storage driver takes advantage of its capabilities such as thin provision and snapshotting to manage images and containers.

It was the default storage driver for CentOS 7 and earlier.

loop-lvm is used to simulate files on the local disk as an actual physical disk or block device by using the ‘loopback’ mechanism. It is because the device-mapper only supports external or block devices.

It is useful for testing purposes only as it provides bad performance.

It is easy to set up as does not require an external device

It requires additional devices to be attached to the local host as it stores data on a separate device.

It is production-ready and provides better performance.

It requires a complex setup to enable direct-lvm.

We need to configure the daemon.json file to use direct-lvm mode. It has multiple options that can be set up as per requirement.

The lvm2 and device-mapper-persistent-data packages must be installed to use device-mapper.

It uses direct-lvm as a backing filesystem.

This storage driver is also part of the main Linux kernel.

It is only supported on SLES ( Suse Linux Enterprise Server) for Docker EE and CS engine.

However, it is recommended for Ubuntu or Debian for Docker Engine – Community edition.

btrfs driver backed by Btrfs filesystem which is a next-generation copy-on-write filesystem.

Btrfs filesystem has many features, for example, block-level operations, thin provisioning, copy-on-write snapshots, etc. these features of Btrfs are used by Docker’s btrfs storage driver to manage images and containers.

It also requires dedicated block storage and must be formatted with Btrfs filesystem, however, we do not require a separate block device if using SLES as it is formatted with Btrfs by default. It is recommended to use additional block devices for better performance.

It is open-sourced under CDDL (Common Development and Distribution License) and created by Sun Microsystems (currently Oracle Corporation).

It is also a next-generation filesystem that has many features like volume management, snapshots, checksumming, compression and deduplication, replication, etc.

It is not part of the mainline Linux kernel because of licensing incompatibilities between the CDDL and GPL.

It is not recommended to use this Docker storage driver for production workloads without substantial experience with ZFS.

It is only supported on Docker CE with Ubuntu 14.04 or higher.

It is not supported on Docker EE or CS-engine.

It is only for testing purposes and not recommended for production use.

The performance is poor for this storage driver.

It can be supported on any filesystem where no copy-on-write filesystem can be used.

Let’s learn some commands to know about Docker’s storage driver with examples: –

We use the ‘docker info’ command to check the default driver used by Docker as below: –

Explanation: – In the above snapshot, we can see that the ‘overlay’ storage driver is used by Docker.

Now we want to configure the Docker to use ‘overlay2’ as a default storage driver, we can do that by editing the ‘daemon.json’ file located at /etc/docker/daemon.json as below: –

Step1: First stop docker service using below command: –

Step2: Add the below configuration to the ‘daemon.json’ file, create the file if it does not exist.

Step3: Start the docker service again as below: –

We can run a container and check which driver is being used by that container: –

$docker run -d --name test_container ubuntu

$docker inspect test_container | grep -i ‘graph’ -A 8

Explanation:– In the above example, we can see that the ‘overlay2’ graph driver or storage driver is being used by a newly created container.

There are numerous distinct storage drivers to be had which might be supported through docker. We need to apprehend the functionality of every driving force and choose which driver is satisfactory suitable for our workloads. We recall three high-degree factors whilst choosing docker’s garage driving force those are ordinary overall performance, shared storage machine, and stability.

Today in this blog, we will discuss Docker Storage Drivers.

Docker Storage Drivers

Docker stockpiling driver, otherwise called diagram driver gives a component to store and oversee pictures and holders on Docker have. Docker utilizes a pluggable design that upholds different capacity drivers. Capacity drivers permit our responsibilities to keep in touch with the compartment's writable layer. There are a few different stockpiling drivers upheld by Docker, we want to pick the best stockpiling driver for our responsibilities. To pick the best stockpiling driver, it is critical to comprehend the most common way of building and putting away pictures in Docker and how these pictures are utilized by compartments. The default stockpiling driver is overlay2 and it is upheld on Docker Engine - Community, and Docker EE 17.06.02-ee5 and up, notwithstanding, we can transform it according to our necessity.

It is the default stockpiling driver presently.

It is upheld by Docker Engine - Community, and Docker EE 17.06.02-ee5 and fresher rendition.

It is fresher and more steady than its unique driver called 'overlay'.

The support filesystem for overlay2 and overlay driver is off.

It is upheld by Linux part form 4.0 or higher, variant 3.10.0-514 or higher of RHEL or CentOS is expected for overlay2 in any case we want to utilize overlay stockpiling driver that isn't suggested.

Overlay2 and overlay drivers go under Linux portion driver OverlayFS stockpiling driver which is a cutting edge association filesystem and it is like aufs, nonetheless, OverlayFs is quicker and simple to execute.

AUFS is an association filesystem, and that implies it presents various indexes called branches in AUFS as a solitary registry on a solitary Linux have. These catalogs are known as layers in Docker.

It was the default stockpiling driver before overlay2 used to oversee pictures and layers on Docker for Ubuntu, and for Debian forms before Stretch. It was the default stockpiling driver in Ubuntu 14.04 and prior.

This driver is great for Platform as a Service where compartment thickness is significant in lighbecausean divides the pictures among various running holders proficiently.

It gives a quick compartment startup and uses less plate space as AUFS divides pictures among different running holders.

It utilizes memory productively, notwithstanding, not effective in composing weighty jobs as latencies are high while keeping in touch with the compartment since it has different catalogs so the record should be found and duplicated to holders top writable layer.

It ought to be utilized with Solid State Drives for quicker read and composes than turning circle and use volumes for composing weighty responsibilities to improve execution.

The support filesystem for AUFS is xfs and ext4 Linux document framework.

It is a square stockpiling driver that stores information in blocks.

It is great for composing composing responsibilities as it stores information at the square level rather than the document level.

It is a portion-based structure and Docker's device-mapper stockpiling driver exploits its capacities like the meager arrangement and snapshotting to oversee pictures and compartments.

It was the default stockpiling driver for CentOS 7 and prior.

circle lvm is utilized to recreate documents on the neighborhood plate as a genuine actual circle or square gadget by utilizing the 'loopback' instrument. It is because of the device-mapper just backings outer or block gadgets.

It is helpful for testing just as it gives terrible execution.

It is not difficult to set up as doesn't need an outside gadget

It requires extra gadgets to be joined to the localhost as it local hosts information on a different gadget.

It is creation prepared and gives better execution.

It requires a mind-boggling arrangement to empower direct-lvm.

We want to design the daemon.json document to utilize direct-lvm mode. It has different choices that can be set up according to the prerequisite.

The lvm2 and gadget mapper-relentless information bundles should be introduced to utilize device-mapper.

It utilizes direct-lvm as a sponsorship filesystem.

This capacity driver is additionally important for the primary Linux portion.

It is just upheld on SLES ( Suse Linux Enterprise Server) for Docker EE and CS motor.

Be that as it may, it is suggested for Ubuntu or Debian for Docker Engine - Community release.

btrfs driver supported by Btrfs filesystem which is a cutting edge duplicate on-compose filesystem.

Btrfs filesystem has many highlights, for instance, block-level tasks, meager provisioning, duplicate on-compose depictions, and so on these elements of Btrfs are utilized by Docker's btrfs stockpiling driver to oversee pictures and holders.

It likewise requires committed square stockpiling and should be designed with Btrfs filesystem, nonetheless, we don't need a separate square gadget assuming involving SLES as it is organized with Btrfs naturally. It is prescribed to involve extra square gadgets for better execution.

It is publicly released under CDDL (Common Development and Distribution License) and made by Sun Microsystems (presently Oracle Corporation).

It is additionally a cutting edge filesystem that has many elements like volume of the executives, depictions, checksumming, pressure and deduplication, replication, and so on

It isn't important for the mainline Linux part due to authorizing contrary qualities between the CDDL and GPL.

It isn't prescribed to involve this Docker stockpiling driver for creation responsibilities without significant involvement in ZFS.

It is just upheld on Docker CE with Ubuntu 14.04 or higher.

It isn't upheld on Docker EE or CS-motor.

It is just for the end goal of testing and not suggested for creation use.

The presentation is poor for this capacity driver.

It tends to be upheld on any filesystem where no duplicate on-compose filesystem can be utilized.

Explanation: – In the above example, we can see that the ‘overlay2’ graph driver or storage driver is being used by a newly created container.

There are a few different stockpiling drivers accessible that are upheld by Docker. We need to comprehend the usefulness of each driver and pick which driver is the most appropriate for our jobs. We consider three undeniable level variables while choosing Docker's stockpiling driver are by and large execution, shared capacity framework, and steadiness.

In this blog post, We will discuss Different Storage Drivers of Docker.

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