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 907A91FF15C for ; Fri, 25 Jul 2025 16:04:44 +0200 (CEST) Received: from firstgate.proxmox.com (localhost [127.0.0.1]) by firstgate.proxmox.com (Proxmox) with ESMTP id C139B19EEC; Fri, 25 Jul 2025 16:06:05 +0200 (CEST) Message-ID: <4533cf05-33a0-4695-a9b3-088dbbfe3df1@proxmox.com> Date: Fri, 25 Jul 2025 16:05:32 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird To: Proxmox VE development discussion , Mira Limbeck References: <20250725113922.99886-1-f.weber@proxmox.com> <73cae5cf-3035-4cb8-9583-c71d7a8fd337@proxmox.com> <3027d138-99d3-419c-a124-7edc8a4f5623@proxmox.com> Content-Language: en-US From: Friedrich Weber In-Reply-To: <3027d138-99d3-419c-a124-7edc8a4f5623@proxmox.com> X-Bm-Milter-Handled: 55990f41-d878-4baa-be0a-ee34c49e34d2 X-Bm-Transport-Timestamp: 1753452329423 X-SPAM-LEVEL: Spam detection results: 0 AWL 0.012 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 SPF_HELO_NONE 0.001 SPF: HELO does not publish an SPF Record SPF_PASS -0.001 SPF: sender matches SPF record Subject: Re: [pve-devel] [PATCH docs v2] pvecm, network: add section on corosync over bonds X-BeenThere: pve-devel@lists.proxmox.com X-Mailman-Version: 2.1.29 Precedence: list List-Id: Proxmox VE development discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Proxmox VE development discussion Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: pve-devel-bounces@lists.proxmox.com Sender: "pve-devel" On 25/07/2025 14:23, Mira Limbeck wrote: > > > On 7/25/25 13:50, Friedrich Weber wrote: >> On 25/07/2025 13:39, Friedrich Weber wrote: >>> [...] >>> +Corosync Over Bonds >>> +~~~~~~~~~~~~~~~~~~~ >>> + >>> +Using a xref:sysadmin_network_bond[bond] as the only Corosync link can be >>> +problematic in certain failure scenarios. If one of the bonded interfaces fails >>> +and stops transmitting packets, but its link state stays up, some bond modes >>> +may cause a state of asymmetric connectivity where cluster nodes can only >>> +communicate with different subsets of other nodes. In case of asymmetric >>> +connectivity, Corosync may not be able to form a stable quorum in the cluster. >>> +If this state persists and HA is enabled, nodes may fence themselves, even if >>> +their respective bond is still fully functioning. In the worst case, the whole >>> +cluster may fence itself. >>> + >>> +For this reason, our recommendations are as follows. >>> + >>> +* We recommend a dedicated physical NIC for the primary Corosync link. Bonds >>> + can be used as additional links for increased redundancy. >> >> These recommendations are still not 100% clear: Are we fine with a setup >> with >> >> - link 0: dedicated corosync link >> - link 1: corosync link over a bond with a problematic mode (such as >> balance-rr or LACP with bond-lacp-rate slow) >> >> ? >> In my tests, as long as the dedicated link 0 is completely online, it >> doesn't matter if a bond runs into the failure scenario above (one of >> the bonded NICs stops transmitting packets), corosync will just continue >> using link 0. But as soon as link 0 goes down and the failure scenario >> happens, the whole-cluster fence may happen. So should our >> recommendation be the relatively strict "if you put corosync on a bond >> (even if it is only a redundant link), use only active-backup or >> LACP+bond-lacp-rate fast"? > > I'd say yes, the recommendation should be either dedicated link > directly, or a bond as redundant link with active-backup or > LACP+lacp-rate fast only. Thanks for the input. I've rephrased the section (and did some other adjustments) to make it clear that the caveats apply whenever a bond is used for corosync traffic. v3: https://lore.proxmox.com/pve-devel/20250725140312.250936-1-f.weber@proxmox.com/T/ _______________________________________________ pve-devel mailing list pve-devel@lists.proxmox.com https://lists.proxmox.com/cgi-bin/mailman/listinfo/pve-devel