The original post: /r/datahoarder by /u/sep222 on 2025-03-24 15:49:56.
I just started using mergerfs + snapraid and I'm having a really hard time with syncing. Snapraid sync typically runs smoothly through about 40GB running at 200 MB/s or more but then falls off a cliff and slowly gets all the way down to 1 MB/s, making it unusable.
I've been trying to use the official documentation but also chatgpt and claude to troubleshoot. The chatbots typically run me through troubleshooting steps with disk read and write speeds but everything always comes back clean. The drives aren't the greatest but they aren't in bad health either.
Writing and reading tests on both drives are ~130MB/s
Troubleshooting steps:
-
enabled disk cache on all drives (hdparm -W 1 /dev/sdX)
-
ran fsck on all drives
-
reformatted parity drive
-
adjusted fstab attributes for mergerfs (see below snapraid.conf)
-
changed block_size in snapraid.conf
-
started snapraid setup from scratch multiple times
2 14TB media drives
1 14TB parity drive
*I'd like to add that I did have one successful sync which ran at a constant 138MB/s throughout. After that sync worked, I waited about a day and ran the sync again after adding over 100GB of data and it was back to the same problem of 1MB/s. I have deleted that parity file and all of snapraid content files to start from scratch multiple times
# SnapRAID configuration
block_size 512
# Parity file
parity /mnt/parity/snapraid.parity
# Content files
content /mnt/etc/snapraid/snapraid.content
content /mnt/plex.main/snapraid.content
content /mnt/plex.main2/snapraid.content
# Data disks
data d1 /mnt/plex.main/
data d2 /mnt/plex.main2/
# Excludes
exclude *.unrecoverable
exclude *.temp
exclude *.tmp
exclude /tmp/
exclude /lost+found/
exclude .DS_Store
exclude .Thumbs.db
exclude ._.Trashes
exclude .fseventsd
exclude .Spotlight-V100
exclude .recycle/
exclude /***/__MACOSX/
exclude .localized
# Auto save during sync
autosave 500
______________________________________________
#/etc/fstab
all media drives and parity drive attributes:
- ext4 defaults,auto,users,rw,nofail,noatime 0 0
mergerfs attributes:
- defaults,allow_other,use_ino,cache.files=partial,dropcacheonclose=true,category.create=mfs 0 0