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 71FB31FF15C for ; Fri, 25 Jul 2025 13:48:50 +0200 (CEST) Received: from firstgate.proxmox.com (localhost [127.0.0.1]) by firstgate.proxmox.com (Proxmox) with ESMTP id 89D9B1705E; Fri, 25 Jul 2025 13:50:09 +0200 (CEST) Message-ID: <73cae5cf-3035-4cb8-9583-c71d7a8fd337@proxmox.com> Date: Fri, 25 Jul 2025 13:50:06 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird From: Friedrich Weber To: pve-devel@lists.proxmox.com References: <20250725113922.99886-1-f.weber@proxmox.com> Content-Language: en-US In-Reply-To: <20250725113922.99886-1-f.weber@proxmox.com> X-Bm-Milter-Handled: 55990f41-d878-4baa-be0a-ee34c49e34d2 X-Bm-Transport-Timestamp: 1753444202930 X-SPAM-LEVEL: Spam detection results: 0 AWL 0.011 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 0.001 ADMINISTRATOR NOTICE: The query to Validity was blocked. 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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 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"? > + > +* We *advise against* using bond modes *balance-rr*, *balance-xor*, > + *balance-tlb*, or *balance-alb* for Corosync traffic. As explained above, > + they can cause asymmetric connectivity in certain failure scenarios. > + > +* *IEEE 802.3ad (LACP)*: This bond mode can cause asymmetric connectivity in > + certain failure scenarios as explained above, but it can recover from this > + state, as each side can stop using a bonded interface if it has not received > + three LACPDUs in a row. However, with default settings, LACPDUs are only sent > + every 30 seconds, yielding a failover time of 90 seconds. This is too long, > + as nodes with HA resources will fence themselves already after roughly one > + minute without a stable quorum. If LACP bonds are used for corosync traffic, > + we recommend setting `bond-lacp-rate fast` *on the Proxmox VE node and the > + switch*! Setting this option on one side requests the other side to send an > + LACPDU every second. Setting this option on both sides can reduce the > + failover time in the scenario above to 3 seconds and thus prevent fencing. > + > +* Bond mode *active-backup* will not cause asymmetric connectivity in the > + failure scenario described above, but the affected node may lose connection > + to the cluster and, if HA is enabled, fence itself. > + > Separate Cluster Network > ~~~~~~~~~~~~~~~~~~~~~~~~ > _______________________________________________ pve-devel mailing list pve-devel@lists.proxmox.com https://lists.proxmox.com/cgi-bin/mailman/listinfo/pve-devel