Help on BTRFS setup
Help on BTRFS setup
I'm attempting a new install. I want to use btrfs with swapfile.
Do I need to disable compression on my swap subvolume?
Is there anything else I should keep in mind for fstab if I want to, say, not keep track of my Downloads folder when snapshotting?
Here is my fstab:
LABEL=arch@btrfs / btrfs rw,relatime,discard=async,space_cache=v2,subvolid=256,subvol=>
LABEL=arch@btrfs /home btrfs rw,relatime,discard=async,space_cache=v2,subvolid=257,subvol=>
LABEL=arch@btrfs /var/cache/pacman/pkg btrfs rw,relatime,discard=async,space_cache=v2,subvolid=259>
LABEL=arch@btrfs /var/log btrfs rw,relatime,discard=async,space_cache=v2,subvolid=258,subvol=>
LABEL=arch@btrfs /.snapshots btrfs rw,relatime,discard=async,space_cache=v2,subvolid=260,subvol=>
LABEL=arch@btrfs /swap btrfs rw,relatime,discard=async,space_cache=v2,subvolid=263,subvol=>
LABEL=efi@fat32 /efi vfat rw,relatime,fmask=0022,dmask=0022,codepage=437,iocharset=asci>
/swap/swapfile none swap defaults 0 0
Do I need to disable compression on my swap subvolume?
https://wiki.archlinux.org/title/Btrfs#Swap_file
Is there anything else I should keep in mind for fstab if I want to, say, not keep track of my Downloads folder when snapshotting?
Just create a separate subvolume for it. Snapshots do not work recursively, so it will be left alone.
Mount options also only take effect on the first mount of the device. Since it looks like you only have 1 btrfs device - only
/needs the options, really.Mount options also only take effect on the first mount of the device. Since it looks like you only have 1 btrfs device - only / needs the options, really.
I didn't know this. Thanks!
Glad I could help! Just to make things a bit clearer - this is a btrfs thing. Other FSes behave differently.
Do I need to disable compression on my swap subvolume?
Short: No
Long: it doesn't matter when mounting multiple subvolumes of the same btrfs partition the options from the first one (usually /) will apply to all. So even if you disable it, that will be ignored.
The old way of creating swap shows the chattr +C line which disables CoW. The same method should work for your Downloads folder since CoW is needed for snapshotting.
Looks good. I also add compress=zstd to / subvolume. I don't add discard because it's set up in LUKS for me. I also don't use a separate subvolume for /var/log, so where possible, compression is used. Journald auto adds +C attr to prevent COW being active on those files because it's unnecessary. I also use a separate swapfile instead of a separate fs.