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https://github.com/dm-vdo/vdo

Userspace tools for managing VDO volumes.
https://github.com/dm-vdo/vdo

compression deduplication storage vdo

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Userspace tools for managing VDO volumes.

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README 

        
# vdo



A set of userspace tools for managing pools of deduplicated and/or compressed

block storage.



## Background



VDO is a device-mapper target that provides inline block-level deduplication,

compression, and thin provisioning capabilities for primary storage. VDO

is managed through LVM and can be integrated into any existing storage stack.



Deduplication is a technique for reducing the consumption of storage resources

by eliminating multiple copies of duplicate blocks. Compression takes the

individual unique blocks and shrinks them with coding algorithms; these reduced

blocks are then efficiently packed together into physical blocks. Thin

provisioning manages the mapping from logical block addresses presented by VDO

to where the data has actually been stored, and also eliminates any blocks of

all zeroes.



With deduplication, instead of writing the same data more than once each

duplicate block is detected and recorded as a reference to the original

block. VDO maintains a mapping from logical block addresses (presented to the

storage layer above VDO) to physical block addresses on the storage layer

under VDO. After deduplication, multiple logical block addresses may be mapped

to the same physical block address; these are called shared blocks and are

reference-counted by the software.



With VDO's compression, blocks are compressed with the fast LZ4 algorithm, and

collected together where possible so that multiple compressed blocks fit within

a single 4 KB block on the underlying storage. Each logical block address is

mapped to a physical block address and an index within it for the desired

compressed data. All compressed blocks are individually reference-counted for

correctness.



Block sharing and block compression are invisible to applications using the

storage, which read and write blocks as they would if VDO were not present.

When a shared block is overwritten, a new physical block is allocated for

storing the new block data to ensure that other logical block addresses that

are mapped to the shared physical block are not modified.



This repository contains a set of userspace tools for managing VDO volumes.

These include "vdoformat" for creating new volumes, "vdostats" for extracting

statistics from those volumes, and a variety of support and debugging tools

which should not be necessary during ordinary operation.



## History



VDO was originally developed by Permabit Technology Corp. as a proprietary set

of kernel modules and userspace tools. This software and technology has been

acquired by Red Hat and relicensed under the GPL (v2 or later). The kernel

module has been merged into the upstream Linux kernel as dm-vdo.



## Documentation



- [RHEL9 VDO Documentation](https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/9/html/deduplicating_and_compressing_logical_volumes_on_rhel/index)

- [RHEL8 VDO Documentation](https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/8/html/deduplicating_and_compressing_storage/index)

- [RHEL7 VDO Integration Guide](https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html/storage_administration_guide/vdo-integration)

- [RHEL7 VDO Evaluation Guide](https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html/storage_administration_guide/vdo-evaluation)



## Releases



The master branch of this repository is intended to be compatible with the most

recent version of the Linux kernel. These packages are available in active

Fedora releases with matching kernel versions.



Version | Oldest Supported Linux Kernel Version 

------- | --------------------------------------

8.3.x.x | 6.9.0



Each older branch of this repository is intended to work with a specific

release of Enterprise Linux (Red Hat Enterprise Linux, CentOS, etc.).



Version | Intended Enterprise Linux Release

------- | ---------------------------------

6.1.x.x | EL7 (3.10.0-*.el7)

6.2.x.x | EL8 (4.18.0-*.el8)

8.2.x.x | EL9 (5.14.0-*.el9)



* Pre-built versions with the required modifications for older Fedora releases

  can be found [here](https://copr.fedorainfracloud.org/coprs/rhawalsh/dm-vdo)

  and can be used by running `dnf copr enable rhawalsh/dm-vdo`.



## Building



In order to build the user-level programs, invoke the following command

from the top directory of this tree:



        make



After building the user-level programs, they may be installed in the

standard locations by invoking the following command from the top directory

of this tree, as the root user:



        make install



## Communication Channels and Contributions



Community feedback, participation and patches are welcome to the

[vdo-devel](https://github.com/dm-vdo/vdo-devel) repository, which is the

parent of this one. This repository does not accept pull requests.



## Licensing



[GPL v2.0 or later](https://www.gnu.org/licenses/old-licenses/gpl-2.0.en.html).

All contributions retain ownership by their original author, but must also be

licensed under the GPL 2.0 or later to be merged.