Re: [PATCH docs v9 5/5] fix #7339: lvm: document discard option

[Fiona Ebner <f.ebner@proxmox.com>]

Am 13.07.26 um 6:00 PM schrieb Lukas Sichert:
> Document the new `on-volume-remove` property for LVM storage and its
> initial `discard` action.
> 
> Also update the `saferemove` description to match the range-based
> zero-out worker and avoid referring to the old command-specific
> implementation details.
> 
> Signed-off-by: Lukas Sichert <l.sichert@proxmox.com>
> Link: bugzilla.proxmox.com/show_bug.cgi?id=7339
> ---
>  pve-storage-lvm.adoc | 34 +++++++++++++++++++++++++++-------
>  1 file changed, 27 insertions(+), 7 deletions(-)
> 
> diff --git a/pve-storage-lvm.adoc b/pve-storage-lvm.adoc
> index ba78663..3ddb26c 100644
> --- a/pve-storage-lvm.adoc
> +++ b/pve-storage-lvm.adoc
> @@ -44,18 +44,39 @@ accessed by other LVs created later (which happen to be assigned the same
>  physical extents). This is a costly operation, but may be required as a security
>  measure in certain environments.
>  +
> -Storage devices that support the "write zeroes" operation will use `blkdiscard`
> -to zero blocks. Otherwise, a fallback to `cstream` is performed.
> +Storage devices that support the "write zeroes" operation use it to zero blocks.
> +Otherwise, zeroes are written manually. The volume is processed range by range,
> +according to `saferemove-stepsize`.
> +
> +`on-volume-remove`::
> +
> +Configure additional actions to run before an LV is removed.

[marker] for comment below

> ++
> +Set `discard=1` to issue discard (TRIM) requests for the LV's blocks before the
> +LV is removed, so thin-provisioned backing storage, such as a SAN LUN, can
> +reclaim space the LV occupied. This is called "Discard Removed Volumes"
> +in the web UI. Discard is rejected if any backing device in the

"Discard is rejected" is a bit vague. Maybe "Configuring the discard
option fails if..."?

> +LV's volume group is detected as not supporting it.
> ++
> +If wiping or discarding fails, the renamed `del-*` LV is kept and renamed to

This is the first time the del- LV is mentioned. It could be mentioned
at [marker] that the volume is renamed to del- when the cleanup starts.

> +`failed-<N>-del-*`, so one can inspect it, retry cleanup manually, or remove
> +it explicitly.
> ++
> +If `saferemove` and `discard` are both enabled, the LV is processed range by
> +range: one range is zeroed out and then discarded before continuing with the
> +next range. This avoids allocating the whole LV with zeroes on thin-provisioned
> +backing storage before the space can be reclaimed again.
>  
>  `saferemove-stepsize`::
>  
> -Wipe step size in MiB (`blkdiscard -p` parameter value), capped to the maximum
> -step size supported by the underlying storage. Up to 32 MiB (maximum) by
> -default.
> +Wipe step size in MiB, capped to the maximum step size supported by the
> +underlying storage. Up to 32 MiB (maximum) by default.
>  
>  `saferemove_throughput`::
>  
> -Wipe throughput (`cstream -t` parameter value), up to 10 MiB/s by default.
> +Limits wipe throughput. If the backing storage supports the "write zeroes"
> +operation, throughput is unlimited by default. Otherwise, manually written
> +zeroes are limited to 10 MiB/s by default.
>  
>  `snapshot-as-volume-chain`::
>  
> @@ -150,4 +171,3 @@ See Also
>  
>  endif::wiki[]
>  
> -

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