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mergerfs is aFUSE basedunion filesystem gearedtowards simplifying storage and management of files across numerouscommodity storage devices. It is similar tomhddfs,unionfs,aufs,DrivePool,etc.

• Logically combine numerous filesystems/paths into a singlemount point (JBOFS: Just a Bunch of FileSystems)
• Combine paths of the same or different filesystems
• Ability to add or remove filesystems/paths without impacting therest of the data
• Unaffected by individual filesystem failure
• Configurable file selection and creation placement
• File IOpassthroughfor near native IO performance (where supported)
• Works with filesystems of any size
• Works with filesystems ofalmost anytype
• Ignore read-only filesystems when creating files
• Hard links
• Hard linkcopy-on-write /CoW
• Runtime configurable
• Support for extended attributes (xattrs)
• Support for file attributes (chattr)
• Support for POSIX ACLs

• Read/write overlay on top of read-only filesystem like OverlayFS
• File whiteout
• RAID like parity calculation (seeSnapRAID)
• Redundancy
• Splitting of files across branches

mergerfs logically merges multiple filesystem paths together. Notblock devices, not filesystem mounts, just paths. It acts as a proxyto the underlying filesystem paths. Combining the behaviors of somefunctions and being a selector for others.

When the contents of a directory are requested mergerfs combines thelist of files from each directory, deduplicating entries, and returnsthat list.

When a file or directory is created a policy is first run to determinewhich branch will be selected for the creation.

For functions which change attributes or remove the file the behaviormay be applied to all instances found.

The way in which mergerfs behaves is controlled by theconfig/options/settings. Morespecifically bypolicies.

A         +      B        =       C/disk1           /disk2           /merged|                |                |+-- /dir1        +-- /dir1        +-- /dir1|   |            |   |            |   ||   +-- file1    |   |            |   +-- file1|                |   +-- file2    |   +-- file2|                |   +-- file3    |   +-- file3|                |                |+-- /dir2        |                +-- /dir2|   |            |                |   ||   +-- file4    |                |   +-- file4|                |                ||                +-- /dir3        +-- /dir3|                |   |            |   ||                |   +-- file5    |   +-- file5|                |                |+-- file6        |                +-- file6+-- file7        +-- file7        +-- file7

https://trapexit.github.io/mergerfs/latest/quickstart/

https://trapexit.github.io/mergerfs

https://trapexit.github.io/mergerfs/latest/support/

https://github.com/trapexit/support

Development and support of a project like mergerfs requires asignificant amount of time and effort. The software is released underthe very liberalISClicense and is therefore free to use for personal or commercial uses.

If you are a non-commercial user and find mergerfs and its support valuableand would like to support the project financially it would be verymuch appreciated.

If you are using mergerfs commercially please consider sponsoring theproject to ensure it continues to be maintained and receiveupdates. If custom features are needed feel free tocontact medirectly.