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36
technology/linux/filesystems/MergerFS.md
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@ -3,7 +3,7 @@ repo: https://github.com/trapexit/mergerfs
obj: filesystem
---
# MergerFS
**mergerfs** is a union filesystem geared towards simplifying storage and management of files across numerous commodity storage devices. It is similar to **mhddfs**, **unionfs**, and **aufs**.
**mergerfs** is a union filesystem geared towards simplifying storage and management of files across numerous commodity storage devices. It is similar to **mhddfs**, **unionfs**, and **aufs**.
Usage: `mergerfs -o<options> <branches> <mountpoint>`
@ -54,7 +54,7 @@ WantedBy=default.target
```
## Options
These options are the same regardless of whether you use them with the `mergerfs` commandline program, in fstab, or in a config file.
These options are the same regardless of whether you use them with the `mergerfs` commandline program, in fstab, or in a config file.
| mount option | description |
| ----------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
@ -132,29 +132,29 @@ These options are the same regardless of whether you use them with the `mergerf
### branches
The 'branches' argument is a colon (':') delimited list of paths to be pooled together. It does not matter if the paths are on the same or different filesystems nor does it matter the filesystem type (within reason). Used and available space will not be duplicated for paths on the same filesystem and any features which aren't supported by the underlying filesystem (such as file attributes or extended attributes) will return the appropriate errors.
Branches currently have two options which can be set. A type which impacts whether or not the branch is included in a policy calculation and a individual minfreespace value. The values are set by prepending an `=` at the end of a branch designation and using commas as delimiters. Example: `/mnt/drive=RW,1234`
Branches currently have two options which can be set. A type which impacts whether or not the branch is included in a policy calculation and a individual minfreespace value. The values are set by prepending an `=` at the end of a branch designation and using commas as delimiters. Example: `/mnt/drive=RW,1234`
#### branch mode
- RW: (read/write) - Default behavior. Will be eligible in all policy categories.
- RO: (read-only) - Will be excluded from `create` and `action` policies. Same as a read-only mounted filesystem would be (though faster to process).
- NC: (no-create) - Will be excluded from `create` policies. You can't create on that branch but you can change or delete.
- RO: (read-only) - Will be excluded from `create` and `action` policies. Same as a read-only mounted filesystem would be (though faster to process).
- NC: (no-create) - Will be excluded from `create` policies. You can't create on that branch but you can change or delete.
#### globbing
To make it easier to include multiple branches mergerfs supports [globbing](http://linux.die.net/man/7/glob). **The globbing tokens MUST be escaped when using via the shell else the shell itself will apply the glob itself.**
To make it easier to include multiple branches mergerfs supports [globbing](http://linux.die.net/man/7/glob). **The globbing tokens MUST be escaped when using via the shell else the shell itself will apply the glob itself.**
```
# mergerfs /mnt/hdd\*:/mnt/ssd /media
```
The above line will use all mount points in /mnt prefixed with **hdd** and **ssd**.
The above line will use all mount points in /mnt prefixed with **hdd** and **ssd**.
To have the pool mounted at boot or otherwise accessible from related tools use **/etc/fstab**.
To have the pool mounted at boot or otherwise accessible from related tools use **/etc/fstab**.
```
# <file system> <mount point> <type> <options> <dump> <pass>
/mnt/hdd*:/mnt/ssd /media fuse.mergerfs minfreespace=16G 0 0
```
## Functions, Categories and Policies
The POSIX filesystem API is made up of a number of functions. **creat**, **stat**, **chown**, etc. For ease of configuration in mergerfs most of the core functions are grouped into 3 categories: **action**, **create**, and **search**. These functions and categories can be assigned a policy which dictates which branch is chosen when performing that function.
The POSIX filesystem API is made up of a number of functions. **creat**, **stat**, **chown**, etc. For ease of configuration in mergerfs most of the core functions are grouped into 3 categories: **action**, **create**, and **search**. These functions and categories can be assigned a policy which dictates which branch is chosen when performing that function.
### Functions and their Category classifications
| Category | FUSE Functions |
@ -171,22 +171,22 @@ A policy's behavior differs, as mentioned above, based on the function it is use
| Policy | Description |
| --------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| all | Search: For **mkdir**, **mknod**, and **symlink** it will apply to all branches. **create** works like **ff**. |
| epall (existing path, all) | For **mkdir**, **mknod**, and **symlink** it will apply to all found. **create** works like **epff** (but more expensive because it doesn't stop after finding a valid branch). |
| all | Search: For **mkdir**, **mknod**, and **symlink** it will apply to all branches. **create** works like **ff**. |
| epall (existing path, all) | For **mkdir**, **mknod**, and **symlink** it will apply to all found. **create** works like **epff** (but more expensive because it doesn't stop after finding a valid branch). |
| epff (existing path, first found) | Given the order of the branches, as defined at mount time or configured at runtime, act on the first one found where the relative path exists. |
| eplfs (existing path, least free space) | Of all the branches on which the relative path exists choose the branch with the least free space. |
| eplus (existing path, least used space) | Of all the branches on which the relative path exists choose the branch with the least used space. |
| epmfs (existing path, most free space) | Of all the branches on which the relative path exists choose the branch with the most free space. |
| eppfrd (existing path, percentage free random distribution) | Like **pfrd** but limited to existing paths. |
| eprand (existing path, random) | Calls **epall** and then randomizes. Returns 1. |
| eppfrd (existing path, percentage free random distribution) | Like **pfrd** but limited to existing paths. |
| eprand (existing path, random) | Calls **epall** and then randomizes. Returns 1. |
| ff (first found) | Given the order of the branches, as defined at mount time or configured at runtime, act on the first one found. |
| lfs (least free space) | Pick the branch with the least available free space. |
| lus (least used space) | Pick the branch with the least used space. |
| mfs (most free space) | Pick the branch with the most available free space. |
| msplfs (most shared path, least free space) | Like **eplfs** but if it fails to find a branch it will try again with the parent directory. Continues this pattern till finding one. |
| msplus (most shared path, least used space) | Like **eplus** but if it fails to find a branch it will try again with the parent directory. Continues this pattern till finding one. |
| mspmfs (most shared path, most free space) | Like **epmfs** but if it fails to find a branch it will try again with the parent directory. Continues this pattern till finding one. |
| msppfrd (most shared path, percentage free random distribution) | Like **eppfrd** but if it fails to find a branch it will try again with the parent directory. Continues this pattern till finding one. |
| msplfs (most shared path, least free space) | Like **eplfs** but if it fails to find a branch it will try again with the parent directory. Continues this pattern till finding one. |
| msplus (most shared path, least used space) | Like **eplus** but if it fails to find a branch it will try again with the parent directory. Continues this pattern till finding one. |
| mspmfs (most shared path, most free space) | Like **epmfs** but if it fails to find a branch it will try again with the parent directory. Continues this pattern till finding one. |
| msppfrd (most shared path, percentage free random distribution) | Like **eppfrd** but if it fails to find a branch it will try again with the parent directory. Continues this pattern till finding one. |
| newest | Pick the file / directory with the largest mtime. |
| pfrd (percentage free random distribution) | Chooses a branch at random with the likelihood of selection based on a branch's available space relative to the total. |
| rand (random) | Calls **all** and then randomizes. Returns 1 branch. |
| rand (random) | Calls **all** and then randomizes. Returns 1 branch. |