Difference between revisions of "SnapRAID / MergerFS"
From Briki
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* ddrescue will write out a map file containing start positions and sizes (all in bytes). Look for lines ending "-", and convert the hex positions to decimal (we'll call this '''P''') | * ddrescue will write out a map file containing start positions and sizes (all in bytes). Look for lines ending "-", and convert the hex positions to decimal (we'll call this '''P''') | ||
| − | * Get the block size for the disk with <code>tune2fs -l /dev/sdX | grep "Block size"</code> (we'll call this '''B''') | + | * Get the block size for the disk with <code>tune2fs -l /dev/sdX | grep "Block size"</code> (we'll call this '''B'''). In my case this is 4096. |
| − | * Get the sector size for the disk with <code>fdisk -l /dev/sdX | grep Units</code> (we'll call this '''S''') | + | * Get the sector size for the disk with <code>fdisk -l /dev/sdX | grep Units</code> (we'll call this '''S'''). In my case this is 512. |
| − | * Identify the starting sector for the /dev/sdXY volume (eg. /dev/sda1) with <code>fdisk -l /dev/sdX</code> (we'll call this '''T''') | + | * Identify the starting sector for the /dev/sdXY volume (eg. /dev/sda1) with <code>fdisk -l /dev/sdX</code> (we'll call this '''T'''). In my case this is 2048. |
* To work out the volume block from the ddrescue position we need to calculate <code>(P - (T * S)) / B</code> | * To work out the volume block from the ddrescue position we need to calculate <code>(P - (T * S)) / B</code> | ||
Revision as of 15:39, 7 March 2022
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). Look for lines ending "-", and convert the hex positions to decimal (we'll call this P)
- Get the block size for the disk with
tune2fs -l /dev/sdX | 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. - To work out the volume block from the ddrescue position we need to calculate
(P - (T * S)) / B
More details:
