[pve-devel] [RFC PATCH 1/2] install: btrfs: fix raid level falling back to single mode

[Fabio Fantoni]

Il 10/01/2025 18:00, Daniel Kral ha scritto:
>  From a user's perspective, the BTRFS single mode has been removed since
> d85180e ("tui: rename raid levels 0/1 to align with GUI installer"). The
> user can now only select at least the "RAID0" level, but if a user
> selects any raid level with only one disk configured on the system,
> BTRFS will be setup in 'single' mode instead of the chosen raid level.
>
> The TUI installer has a separate check for this, but the GUI installer
> as well as the auto installer will silently fallback to single mode,
> which could be confusing for and unwanted by the user.
>
> Therefore, remove the BTRFS single mode from being selected when
> configuring disks in the GUI installer and during the installation in
> general, which makes the auto installer fail if the wrong amount of
> disks are selected for the specified raid level. This makes btrfs' raid
> disk count validation align with the one from zfs.
>
> Signed-off-by: Daniel Kral <d.kral at proxmox.com>
> ---
>
> Discussion
>
> BTRFS didn't allow a single-disk RAID0 configuration before kernel 5.15
> and AFAIK also silently used the single profile for that case, but this
> has changed since then.
>
> If we want users to still be able to create a BTRFS filesystem in single
> mode (which seems very reasonable), I can do a v2 or followup to add a
> "btrfs (single)" entry to the disk setup.
Hi, I think is better to add also "single" mode
>
> Testing
>
> I have tested this by the usual installer test procedure (debug shell,
> patch files, launch target installer manually) and the GUI installer
> disallows creating a btrfs raid1 or raid10 with only one disk, but
> allows it with at least the correct amount of disks. The same applies to
> the autoinstaller with the same test cases.
>
> Unpatched a single-disk RAID0 install resulted in:
>
> ```
> root at pve:~# btrfs filesystem usage -T .
> [ ... ]
>               Data   Metadata  System
> Id Path      single single    single   Unallocated Total    Slack
> -- --------- ------ --------- -------- ----------- -------- -------
>   1 /dev/sda3 4.01GB 520.00MiB  4.00MiB    26.98GiB 31.50GiB 3.50KiB
> [ ... ]
> ```
>
> and patched a single-disk RAID0 install results in:
>
> ```
> ```
> root at pve:~# btrfs filesystem usage -T .
> [ ... ]
>               Data   Metadata  System
> Id Path      RAID0  RAID0     RAID0    Unallocated Total    Slack
> -- --------- ------ --------- -------- ----------- -------- -------
>   1 /dev/sda3 4.00GB 512.00MiB  8.00MiB    26.99GiB 31.50GiB 3.50KiB
> [ ... ]
> ```
> ```
>
>   Proxmox/Install.pm | 22 +++++++++-------------
>   1 file changed, 9 insertions(+), 13 deletions(-)
>
> diff --git a/Proxmox/Install.pm b/Proxmox/Install.pm
> index c0a17b2..b72a83e 100644
> --- a/Proxmox/Install.pm
> +++ b/Proxmox/Install.pm
> @@ -359,20 +359,16 @@ sub get_btrfs_raid_setup {
>   
>       my $mode;
>   
> -    if ($diskcount == 1) {
> -	$mode = 'single';
> +    if ($filesys eq 'btrfs (RAID0)') {
> +	$mode = 'raid0';
> +    } elsif ($filesys eq 'btrfs (RAID1)') {
> +	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;
> +	$mode = 'raid10';
>       } else {
> -	if ($filesys eq 'btrfs (RAID0)') {
> -	    $mode = 'raid0';
> -	} elsif ($filesys eq 'btrfs (RAID1)') {
> -	    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;
> -	    $mode = 'raid10';
> -	} else {
> -	    die "unknown btrfs mode '$filesys'\n";
> -	}
> +	die "unknown btrfs mode '$filesys'\n";
>       }
>   
>       return ($devlist, $mode);



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