From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from firstgate.proxmox.com (firstgate.proxmox.com [IPv6:2a01:7e0:0:424::9]) by lore.proxmox.com (Postfix) with ESMTPS id 0191D1FF13B for ; Wed, 11 Mar 2026 14:35:46 +0100 (CET) Received: from firstgate.proxmox.com (localhost [127.0.0.1]) by firstgate.proxmox.com (Proxmox) with ESMTP id B2FF01C4FA; Wed, 11 Mar 2026 14:35:39 +0100 (CET) Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Wed, 11 Mar 2026 14:35:04 +0100 Message-Id: Subject: Re: [PATCH docs v2 1/2] local-zfs: rephrase ARC limit To: "Maximiliano Sandoval" X-Mailer: aerc 0.20.0 References: <20260226084639.107816-1-m.sandoval@proxmox.com> <20260226084639.107816-2-m.sandoval@proxmox.com> In-Reply-To: <20260226084639.107816-2-m.sandoval@proxmox.com> From: "Shannon Sterz" X-Bm-Milter-Handled: 55990f41-d878-4baa-be0a-ee34c49e34d2 X-Bm-Transport-Timestamp: 1773236069952 X-SPAM-LEVEL: Spam detection results: 0 AWL -0.947 Adjusted score from AWL reputation of From: address BAYES_00 -1.9 Bayes spam probability is 0 to 1% DMARC_MISSING 0.1 Missing DMARC policy KAM_DMARC_STATUS 0.01 Test Rule for DKIM or SPF Failure with Strict Alignment RCVD_IN_VALIDITY_CERTIFIED_BLOCKED 0.408 ADMINISTRATOR NOTICE: The query to Validity was blocked. See https://knowledge.validity.com/hc/en-us/articles/20961730681243 for more information. RCVD_IN_VALIDITY_RPBL_BLOCKED 0.819 ADMINISTRATOR NOTICE: The query to Validity was blocked. See https://knowledge.validity.com/hc/en-us/articles/20961730681243 for more information. RCVD_IN_VALIDITY_SAFE_BLOCKED 0.903 ADMINISTRATOR NOTICE: The query to Validity was blocked. See https://knowledge.validity.com/hc/en-us/articles/20961730681243 for more information. SPF_HELO_NONE 0.001 SPF: HELO does not publish an SPF Record SPF_PASS -0.001 SPF: sender matches SPF record Message-ID-Hash: W4CPF3BXNJWZCB3KDNMYH6HKX4ZQWJVB X-Message-ID-Hash: W4CPF3BXNJWZCB3KDNMYH6HKX4ZQWJVB X-MailFrom: s.sterz@proxmox.com X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; loop; banned-address; emergency; member-moderation; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header CC: pve-devel@lists.proxmox.com X-Mailman-Version: 3.3.10 Precedence: list List-Id: Proxmox VE development discussion List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: On Thu Feb 26, 2026 at 9:46 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. > > We also document ZFS' default size. See [zfs-6a629f3] for more details. > > This also frames the problem for pre-existing setups in its own > paragraph. > > [zfs-6a629f3] https://github.com/openzfs/zfs/commit/6a629f32344468ae81b26= 4055916641480cb438d > > Signed-off-by: Maximiliano Sandoval > --- > local-zfs.adoc | 13 +++++++++---- > 1 file changed, 9 insertions(+), 4 deletions(-) > > diff --git a/local-zfs.adoc b/local-zfs.adoc > index 85fa092..b3a462d 100644 > --- a/local-zfs.adoc > +++ b/local-zfs.adoc > @@ -586,10 +586,15 @@ 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+, fo= r the > +**A**daptive **R**eplacement **C**ache (ARC) by default. This value is w= ritten > +to `/etc/modprobe.d/zfs.conf` during installation. > + > +Before {pve} 8.1, the ARC usage limit was not set during installation an= d > +matched ZFS' default value which was either 62.5% starting on ZFS 2.3.0 = or 50% nit: i think "starting with" sounds more natural in english > +for older versions. For existing installations that predate {pve} 8.1, m= anual > +steps would have to be performed in order to lower the usage limit as de= scribed > +below. > > Allocating enough memory for the ARC is crucial for IO performance, so r= educe it > with caution. As a general rule of thumb, allocate at least +2 GiB Base = + 1