From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9B9B2273816 for ; Sat, 2 May 2026 11:41:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777722105; cv=none; b=F89dYnjPBofYApjpaOH6D7V4baygCLMDyo3fRGdjS9N4ij3BacT17uikNMpQG4cRnJcKBoYWcZCD2bCTCIEq77KKndkmfDZXg34WEYFuBwNTHmLPGQ6Alguv7afIHy9W0Pdz6DNRttjlPDNItB/ZP4DLBUi1LlNZY/iqSpRAAe4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777722105; c=relaxed/simple; bh=XQnsbGpN/kxMk5Zz8/L2zvlr+6flATk8ET1zzPBpmVA=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=I+cbhCmY1JgqRyh9ykU1VusHUyWyu5JxEKHo2buFuEmf7LKZoCCw47Yw4b/gtKgm+ZRGt98meftCfESAr0F4k4tt7LpNGDtntJcdxL4wcbtd3J7avXfjH041zK3dN5pSrOxk/G3WJlZhpulg6Ix24sa7zuRhfE/Gs/mC/FzsltE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=VaDEa38c; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="VaDEa38c" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 08809C19425; Sat, 2 May 2026 11:41:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1777722105; bh=XQnsbGpN/kxMk5Zz8/L2zvlr+6flATk8ET1zzPBpmVA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=VaDEa38cgh6MTu3rs9rJ6eODBlK/PlEzqISK1EJ9eL7HhyDdC/kS45Ky7phwijzzm oUdESmWKD7TmpYpCs+fKgfmrxJVMCLo06ofEIbo1LRxuVq0VpN1X5dPObD6DLWryC1 l+dVsw6qTBgghBSnfL5QZCPmXSItCeHajtZ59pMNNCojoJYtHFjaRFA0VUaYv7ejor KsRsVY2PjukPP8Mlt9Oitig6khgvgxXjzI8IB0oqU6TeqJfPy6cRwT8aTY3lHGVLvt BuRrTNLqh5e5MogxxlcaslQ5HULjYWGix1Y+IAKDAz5cUdxaJEqQqAN9aJ20MPMu2G quK6ZcUb+iHhQ== Date: Sat, 2 May 2026 12:41:41 +0100 From: Keith Busch To: Matthew Wilcox Cc: Haris Iqbal , lsf-pc@lists.linux-foundation.org, linux-block@vger.kernel.org, Jia Li Subject: Re: [Lsf-pc] [LSF/MM/BPF TOPIC] A block level, active-active replication solution Message-ID: References: Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Fri, May 01, 2026 at 08:47:35PM +0100, Matthew Wilcox wrote: > On Tue, Feb 03, 2026 at 04:09:59PM +0100, Haris Iqbal via Lsf-pc wrote: > > We are working on a pair of kernel modules which would offer a new > > replication solution in the Linux kernel. It would be a block level, > > active-active replication solution for RDMA transport. > > Why is active-active a good idea? > > With an active-passive solution, network traffic is directed to the > active node. Over time at some point we get close to saturating the > link and performance drops. At that point, human intervention will > occur and the network link will be upgraded. > > With an active-active solution, traffic goes to each node. At smoe point > each link will be about 75% utilised and we won't see any performance > problems. But then a node goes down and all of a sudden the remaining > node is being hit with 150% of the link capacity. There's no gradual > degradation here; the whole solution just goes down. Maybe I'm out of touch with reality, but I could swear active-passive setups are often configured such that the passive node for one resource is the active node for another. That would also suffer the same link capacity issues you're describing.