Re: [PATCH docs 1/2] local-zfs: Rephrase ARC limit

["Shannon Sterz" <s.sterz@proxmox.com>]

On Tue Feb 24, 2026 at 11:54 AM CET, Maximiliano Sandoval wrote:
> We rephrase the current section putting more emphasis on the current
> state of things given than Proxmox VE 8.1 was released over two years
> ago.
>
> This also frames the problem for pre-existing setups in its own
> paragraph.
>
> Signed-off-by: Maximiliano Sandoval <m.sandoval@proxmox.com>
> ---
>  local-zfs.adoc | 11 +++++++----
>  1 file changed, 7 insertions(+), 4 deletions(-)
>
> diff --git a/local-zfs.adoc b/local-zfs.adoc
> index 4f20d00..12506d1 100644
> --- a/local-zfs.adoc
> +++ b/local-zfs.adoc
> @@ -586,10 +586,13 @@ configured for the root user.
>  Limit ZFS Memory Usage
>  ~~~~~~~~~~~~~~~~~~~~~~
>
> -ZFS uses '50 %' of the host memory for the **A**daptive **R**eplacement
> -**C**ache (ARC) by default. For new installations starting with {pve} 8.1, the
> -ARC usage limit will be set to '10 %' of the installed physical memory, clamped
> -to a maximum of +16 GiB+. This value is written to `/etc/modprobe.d/zfs.conf`.
> +ZFS uses '10 %' of the host memory, clamped to a maximum of +16 GiB+, for the
> +**A**daptive **R**eplacement **C**ache (ARC) by default. This value is written
> +to `/etc/modprobe.d/zfs.conf` during installation.
> +
> +Before {pve} 8.1, the ARC usage limit was set to '50 %' without clamping it to a
> +maximum size. For existing installations that predate {pve} 8.1, manual steps
> +would have to be performed in order to lower the usage limit as described below.

this and the other patch in this series looks good to me, one small
comment: maybe mention that this isn't something set by the installer or
pve, but rather just the zfs default [1].

[1]: https://openzfs.github.io/openzfs-docs/man/master/4/zfs.4.html#zfs_arc_max

other than that, consider this:

Reviewed-by: Shannon Sterz <s.sterz@proxmox.com>

>
>  Allocating enough memory for the ARC is crucial for IO performance, so reduce it
>  with caution. As a general rule of thumb, allocate at least +2 GiB Base + 1