[pve-devel] [RFC PATCH 2/2] common: btrfs: lower minimum amount of disks for raid10 to 2

[Fabio Fantoni]

Il 10/01/2025 18:00, Daniel Kral ha scritto:
> As the installer allows single-disk RAID0 configurations and BTRFS
> allows to create a filesystem with the RAID10 profile with only two
> disks since kernel version 5.15 [0], lower the minimum amount of disks
> the installer requires for a BTRFS RAID10 setup.
>
> The motiviation for this is to allow users to create a BTRFS RAID10
> configuration even though they do not have the necessary disks ready at
> setup time itself without needing to convert the profile afterwards.

btrfs profiles work differently but other hardware or software raids, 
many users may not inform themselves well beforehand but even in the 
case of informed users even if technically now btrfs allows lower limits 
with the creation of raid 0 (and raid10) I think it would be better to 
keep them at the base at the creation and then it must be the user who 
consciously makes any subsequent conversions.

regarding btrfs profiles at creation, one thing that could be useful is 
to always put duplicate metadata (dup with single disk or raid 1 in the 
case of raid0), if you don't want it by default maybe put it as an 
additional option, and if you don't want that either at least add it to 
the documentation (as a suggestion if you want greater resilience of the 
filesystem without consuming excessive space)

>
> [0] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=b2f78e88052bc0bee56bbf646d245fcfb431a873
>
> Signed-off-by: Daniel Kral <d.kral at proxmox.com>
> ---
> Discussion
>
> If this patch seems like something worthwile, I think it would be
> necessary to have some sort of warning popup for 2 <= $diskcount < 4 in
> RAID10, and maybe also the same for $diskcount == 1 in RAID0, that
> there's no advantage to create a degenerate RAID0/10 without planning to
> add at least 1/2 disks later. I would add this in a v2 or followup if
> this gets ACKed.
>
>   Proxmox/Install.pm                          | 2 +-
>   proxmox-installer-common/src/disk_checks.rs | 6 +++---
>   2 files changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/Proxmox/Install.pm b/Proxmox/Install.pm
> index b72a83e..d52d17b 100644
> --- a/Proxmox/Install.pm
> +++ b/Proxmox/Install.pm
> @@ -365,7 +365,7 @@ sub get_btrfs_raid_setup {
>   	die "btrfs (RAID1) needs at least 2 devices\n" if $diskcount < 2;
>   	$mode = 'raid1';
>       } elsif ($filesys eq 'btrfs (RAID10)') {
> -	die "btrfs (RAID10) needs at least 4 devices\n" if $diskcount < 4;
> +	die "btrfs (RAID10) needs at least 2 devices\n" if $diskcount < 2;
>   	$mode = 'raid10';
>       } else {
>   	die "unknown btrfs mode '$filesys'\n";
> diff --git a/proxmox-installer-common/src/disk_checks.rs b/proxmox-installer-common/src/disk_checks.rs
> index ecc43bd..bd1c54c 100644
> --- a/proxmox-installer-common/src/disk_checks.rs
> +++ b/proxmox-installer-common/src/disk_checks.rs
> @@ -129,7 +129,7 @@ pub fn check_btrfs_raid_config(level: BtrfsRaidLevel, disks: &[Disk]) -> Result<
>       match level {
>           BtrfsRaidLevel::Raid0 => check_raid_min_disks(disks, 1)?,
>           BtrfsRaidLevel::Raid1 => check_raid_min_disks(disks, 2)?,
> -        BtrfsRaidLevel::Raid10 => check_raid_min_disks(disks, 4)?,
> +        BtrfsRaidLevel::Raid10 => check_raid_min_disks(disks, 2)?,
>       }
>   
>       Ok(())
> @@ -204,8 +204,8 @@ mod tests {
>           assert!(check_btrfs_raid_config(BtrfsRaidLevel::Raid1, &disks).is_ok());
>   
>           assert!(check_btrfs_raid_config(BtrfsRaidLevel::Raid10, &[]).is_err());
> -        assert!(check_btrfs_raid_config(BtrfsRaidLevel::Raid10, &disks[..3]).is_err());
> -        assert!(check_btrfs_raid_config(BtrfsRaidLevel::Raid10, &disks[..4]).is_ok());
> +        assert!(check_btrfs_raid_config(BtrfsRaidLevel::Raid10, &disks[..1]).is_err());
> +        assert!(check_btrfs_raid_config(BtrfsRaidLevel::Raid10, &disks[..2]).is_ok());
>           assert!(check_btrfs_raid_config(BtrfsRaidLevel::Raid10, &disks).is_ok());
>       }
>   



-- 
Questa email è stata esaminata alla ricerca di virus dal software antivirus Avast.
www.avast.com