Arch Linux

Pafrapé

Member

Registered: 2010-10-25

Posts: 48

systemd-homed : btrfs or ext4 ?

Hello.
I'm about to perform a fresh installation of Arch Linux.
I'll be using two NVMe drives: one for the system and one for `/home`.
I plan to set up systemd-homed on /home.

A quick question: What is the best type of formatting for the hard drive that will host /home and systemd-homed? Btrfs or ext4?

Thanks for the advice.

Last edited by Pafrapé (Yesterday 07:30:45)

topcat01

Member

Registered: 2019-09-17

Posts: 343

Re: systemd-homed : btrfs or ext4 ?

btrfs should be fine for homed images. I have been switching to btrfs myself because apart from the snapshot and data integrity features, btrfs is great at diagnosing and reporting failing/misbehaving hardware early, before data is lost. The usual caveats apply: do not let "unallocated space" drop too low, and do not use raid5/6.

Pafrapé

Member

Registered: 2010-10-25

Posts: 48

Re: systemd-homed : btrfs or ext4 ?

After research, I think the best way to format my hard drive—which will only contain `/home` and on which I will install `systemd-homed`—is ext4.
Indeed, homed natively uses Btrfs.
Formatting `/home` with Btrfs while `systemd-homed` natively uses Btrfs puts a double load on the CPU and causes instability by performing Copy-on-Write twice simultaneously.
Furthermore, snapshots are not possible with `systemd-homed`.
In conclusion, the ideal setup is to install homed, natively formatted in Btrfs, on a storage medium formatted in ext4.

topcat01

Member

Registered: 2019-09-17

Posts: 343

Re: systemd-homed : btrfs or ext4 ?

Yes, there are a few options. I prefer

homectl create --storage=luks --fs-type=ext4 ...

to keep things simple inside the LUKS container, and keep the loopback file on btrfs, so I can snapshot and back up the containing subvolume (send/receive).

This is the opposite of my approach to (Linux) VM images, where I use ext4 for storing the image, and btrfs inside the VM, since the VM offers full flexibility w.r.t. the filesystem.

Last edited by topcat01 (Yesterday 17:57:38)

Pafrapé

Member

Registered: 2010-10-25

Posts: 48

Re: systemd-homed : btrfs or ext4 ?

Actually, you did the opposite of me:
- /home formatted as btrfs
- homed formatted as ext4.
Is that right?

What are the benefits?