212 lines
5.0 KiB
Markdown
212 lines
5.0 KiB
Markdown
# BTRFS
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- [BTRFS](#btrfs)
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- [Naming Conventions](#naming-conventions)
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- [Creating an Array](#creating-an-array)
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- [Converting an Array Between RAID Versions](#converting-an-array-between-raid-versions)
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- [Mounting the Array](#mounting-the-array)
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- [Adding Disks](#adding-disks)
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- [Replacing a Disk](#replacing-a-disk)
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- [Scrubbing the Array](#scrubbing-the-array)
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- [Creating Subvolumes](#creating-subvolumes)
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- [Monitoring Usage](#monitoring-usage)
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- [Monitoring Disk Health](#monitoring-disk-health)
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- [Defragmenting and Compressing](#defragmenting-and-compressing)
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- [Converting ext4 to btrfs](#converting-ext4-to-btrfs)
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Oracle [has decent docs here](https://docs.oracle.com/en/operating-systems/oracle-linux/8/btrfs/btrfs-ResizingaBtrfsFileSystem.html)
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You'll also want to [read about btrfs compression](https://thelinuxcode.com/enable-btrfs-filesystem-compression/)
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## Naming Conventions
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`poolX` is my naming convention for data pools. `pool0` is the first pool you create.
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`backupX` is my naming convention for backup pools. `backup0` is hte first backup pool you create.
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## Creating an Array
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```bash
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# At any point you can check the status of an array by referencing any member
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btrfs filesystem show /dev/vdb
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```
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```bash
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# Raid0
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mkfs.btrfs --data raid0 --metadata raid0 /dev/vdb /dev/vdc
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btrfs device scan
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# Raid1
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mkfs.btrfs --data raid1 --metadata raid1 /dev/vdb /dev/vdc
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btrfs device scan
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# Raid1c3
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mkfs.btrfs --data raid1c3 --metadata raid1c3 /dev/vdb /dev/vdc /dev/vdd
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btrfs device scan
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# Raid10
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mkfs.btrfs --data raid10 --metadata raid10 /dev/vdb /dev/vdc /dev/vdd /dev/vde
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btrfs device scan
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```
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Label your arrays for easier identification in btrfs filesystem information commands
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```bash
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btrfs filesystem label /btrfs/pool0 pool0
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```
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## Converting an Array Between RAID Versions
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```bash
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# Convert to raid1
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# -dconvert == "data convert"
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# -mconvert == "metadata convert"
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btrfs balance start -dconvert=raid1 -mconvert=raid1 /btrfs/pool0
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btrfs balance status
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```
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## Mounting the Array
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One off
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```bash
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# Create a mount point
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mkdir /btrfs/pool0
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# List the filesystem UUID
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lsblk --fs
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# Mount the top level subvolume
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mount UUID=xxxxx-xxxxx-xxxxx /btrfs/pool0 -o subvolid=5
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# Mount with better SSD support
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mount UUID=xxxxx-xxxxx-xxxxx /btrfs/pool0 -o subvolid=5,ssd
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# Mount with auto defragmentation for HDD support
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mount UUID=xxxxx-xxxxx-xxxxx /btrfs/pool0 -o subvolid=5,autodefrag
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# Mount a subvolume
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mount UUID=xxxxx-xxxxx-xxxxx /btrfs/pool0 -o subvol=home
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# Inspect
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btrfs filesystem show /btrfs/pool0
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```
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In fstab
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```conf
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UUID=btrfs_uuid /btrfs/pool0 btrfs defaults 0 0
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```
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## Adding Disks
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```bash
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# Add a disk
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btrfs device add /dev/vdd /btrfs/pool0
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# Balance the array
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btrfs balance start /btrfs/pool0
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# Watch the expansion
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btrfs filesystem usage /btrfs/pool0
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```
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## Replacing a Disk
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```bash
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# Remove a disk from the array
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# This may take a while, as btrfs will rebalance the array during this process
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btrfs device remove /dev/vdb /btrfs/pool0
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# You can watch the device "used" data drain with
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watch btrfs filesystem show /btrfs/pool0/
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# Add the new device
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# Again, this may take a while while btrfs rebalances.
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btrfs device add /dev/vdg /btrfs/pool0
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```
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## Scrubbing the Array
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```bash
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# Start a scrub to check for errors
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# -B prevents the process from going to the background
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# -d prints stats for each device
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btrfs scrub start -Bd /btrfs/pool0
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# Check the status of a scrub
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btrfs scrub status /btrfs/pool0
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# Watch for disk failures
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dmesg | grep btrfs
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```
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## Creating Subvolumes
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```bash
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# Create a new subvolume (make sure to mount /btrfs as subvolid=5)
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btrfs subvolume create /btrfs/pool0
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# List all subvolumes under a path
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btrfs subvolume list -o /btrfs/pool0
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# Delete a subvolume
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btrfs subvolume delete /btrfs/pool0
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```
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## Monitoring Usage
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```bash
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# Quick info for all btrfs arrays
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btrfs filesystem show
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# Show usage for a specific array
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btrfs filesystem usage /btrfs/pool0
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# Quick command to filter for data used
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btrfs filesystem usage /btrfs/pool0 | grep 'Data.*Used'
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```
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## Monitoring Disk Health
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<https://www.dotlinux.net/blog/how-to-configure-smartd-and-be-notified-of-hard-disk-problems-via-email/#installing-smartd-smartmontools>
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```bash
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# btrfs device stats shows any errors
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# Grep for any line not ending in "0"
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btrfs device stats /btrfs/pool0 | grep -vE ' 0$'
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# Show the device IDs for the mounted filesystem
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btrfs filesystem show /btrfs/pool0
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# Delete a device (with ID 8, for example)
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btrfs device delete 8 /btrfs/pool0
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# Add a device to the array
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btrfs device add /dev/vdi1 /btrfs/pool0
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# Rebalance the array
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btrfs balance start --background --full-balance /btrfs/pool0
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# Check the status
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btrfs balance status /btrfs/pool0
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```
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## Defragmenting and Compressing
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```bash
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# Defrag a filesystem
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btrfs filesystem defragment /btrfs/pool0
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# Defrag and apply compression
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# zstd:20 is currently the best compression algorithm
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btrfs filesystem defragment -c zstd:20 /btrfs/pool0
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```
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## Converting ext4 to btrfs
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```bash
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# Unmount and then run btrfs-convert
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umount /path/to/mount
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btrfs-convert /dev/sdX1
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``` |