mergerfs - a featureful union filesystem
-mergerfs is a -FUSE based -union filesystem geared -towards simplifying storage and management of files across numerous -commodity storage devices. It is similar to mhddfs, unionfs, -and aufs.
-Features
--
-
- Logically combine numerous filesystems/paths into a single - mount point -
- Combine paths of the same or different filesystems -
- Ability to add or remove filesystems/paths without impacting the - rest of the data -
- Unaffected by individual filesystem failure -
- Configurable file selection and creation placement -
- Works with filesystems of any size -
- Works with filesystems of almost any type -
- Ignore read-only filesystems when creating files -
- Hard link copy-on-write / CoW -
- Runtime configurable -
- Support for extended attributes (xattrs) -
- Support for file attributes (chattr) -
- Support for POSIX ACLs -
Non-features
--
-
- Read/write overlay on top of read-only filesystem like OverlayFS -
- File whiteout -
- RAID like parity calculation -
- Redundancy -
- Splitting of files across branches -
How it works
-mergerfs logically merges multiple filesystem paths together. Not -block devices, not filesystem mounts, just paths. It acts as a proxy -to the underlying filesystem paths. Combining the behaviors of some -functions and being a selector for others.
-When the contents of a directory are requested mergerfs combines the -list of files from each directory, deduplicating entries, and returns -that list.
-When a file or directory is created a policy is first run to determine -which branch will be selected for the creation.
-For functions which change attributes or remove the file the behavior -may be applied to all instances found.
-Read more about policies -here.
-Visualization
-A + B = C
-/disk1 /disk2 /merged
-| | |
-+-- /dir1 +-- /dir1 +-- /dir1
-| | | | | |
-| +-- file1 | +-- file2 | +-- file1
-| | +-- file3 | +-- file2
-+-- /dir2 | | +-- file3
-| | +-- /dir3 |
-| +-- file4 | +-- /dir2
-| +-- file5 | |
-+-- file6 | +-- file4
- |
- +-- /dir3
- | |
- | +-- file5
- |
- +-- file6
-Getting Started
-Head to the quick start guide.
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