MergerFS

Brandon Rozek

January 14, 2020

MergerFS is a great filesystem for an expandable storage system in a homelab. Mostly since it allows you to add disks one at a time without having to, for example, resilver a ZFS pool. MergerFS won’t be as efficient as a filesystem that stripes your data across disks, but in the case of a disk failure the disks unaffected will still have part of the data.

Plenty of other people described MergerFS, so I’ll keep this post simple.

First install MergerFS,

sudo apt install mergerfs

The way I have my drives in my homelab setup is to have /mnt/data/N where N is the number of the drive.

Examples: /mnt/data/1, /mnt/data/2, /mnt/data/3

This is mainly so that I can use wildcards to capture all the drives at once.

Temporary mounting solution:

sudo mergerfs -o defaults,allow_other,use_ino,fsname=data /mnt/data/\* $HOME/data

Permanent solution (Edit /etc/fstab)

/mnt/data/* /home/user/data fuse.mergerfs defaults,allow_other,use_ino,fsname=data 0 0

Quick summary of options passed

Option Description
defaults Shortcut for atomic_o_trunc, auto_cache, big_writes, default_permissions, splice_move, splice_read, splice_write
allow_other Allows users beside the mergerfs owner to view the filesystem.
use_ino MergerFS supplies inodes instead of libfuse
fsname Name of the mount as shown in df and other tools