SnapRAID / MergerFS
From Briki
Contents
SnapRAID / MergerFS
Setup
https://zackreed.me/setting-up-snapraid-on-ubuntu/
Note that if (like me) you use a dedicated snapraid content directory then you'll need to create that by hand for each disk with:
mkdir /mnt/data/disk1/.snapraid
Partitioning a new data disk
Note: "-m 2" here reserves 2% of the filesystem for root-owned files (eg. .../.snapraid/content)
sudo parted -a optimal -s /dev/sdX -- mklabel gpt mkpart primary 0% 100% sudo mkfs.ext4 -m 2 -T largefile4 /dev/sdX1
Partitioning a new parity disk
Note: "-m 0" here reserves 0% of the filesystem, ensuring that the parity disks are slightly larger than the data disks
sudo parted -a optimal -s /dev/sdX -- mklabel gpt mkpart primary 0% 100% sudo mkfs.ext4 -m 0 -T largefile4 /dev/sdX1
Adding a new data disk to mergerfs
From: https://zackreed.me/mergerfs-neat-tricks/ From within the root of the mergerfs filesystem (eg. /srv)
xattr -w user.mergerfs.srcmounts '+>/mnt/data/disk4/srv' .mergerfs
Removing a data disk from mergerfs
From within the root of the mergerfs filesystem (eg. /srv)
xattr -w user.mergerfs.srcmounts '-/mnt/data/disk4/srv' .mergerfs
Forcing a resync
sudo snapraid sync
Identifying/Fixing a bad block
- Run ddrescue to identify the failing bytes on the disk:
ddrescue --ask --verbose --binary-prefixes --idirect --force /dev/sdX /dev/null sdX.map
- ddrescue will write out a map file containing start positions and sizes (all in bytes) of good (+) and bad (-) byte ranges
- Get the block size for the volume with
tune2fs -l /dev/sdXY | grep "Block size"(we'll call this B). In my case this is 4096. - Get the sector size for the disk with
fdisk -l /dev/sdX | grep Units(we'll call this S). In my case this is 512. - Identify the starting sector for the /dev/sdXY volume (eg. /dev/sda1) with
fdisk -l /dev/sdX(we'll call this T). In my case this is 2048. - Run ddrescuelog to list out the bad block locations (using the block size B):
ddrescuelog -b B --list-blocks=- sdX.map
- For each of these, convert to a block location in the volume (rather than the disk) by subtracting
(T * S / B). In my case that's 256.
More details:
