From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:35394) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1emG46-0002Ra-F8 for qemu-devel@nongnu.org; Thu, 15 Feb 2018 04:42:55 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1emG41-0000Qn-JQ for qemu-devel@nongnu.org; Thu, 15 Feb 2018 04:42:54 -0500 Received: from latin.grep.be ([2a01:4f8:140:52e5::2]:55522) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1emG41-0000F4-94 for qemu-devel@nongnu.org; Thu, 15 Feb 2018 04:42:49 -0500 Date: Thu, 15 Feb 2018 10:42:20 +0100 From: Wouter Verhelst Message-ID: <20180215094220.GA3203@grep.be> References: <201297396.3423395.1518598461012.JavaMail.zimbra@oxygem.tv> <1564471998.3427173.1518601541505.JavaMail.zimbra@oxygem.tv> <83c0fdee-126f-18f1-a691-053669325cb9@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <83c0fdee-126f-18f1-a691-053669325cb9@redhat.com> Subject: Re: [Qemu-devel] drive-mirroring to nbd is failing with multiple parallel jobs (qemu 2.9 -> 2.11) List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Eric Blake Cc: Alexandre DERUMIER , qemu-devel , nbd list Hi Eric, On Wed, Feb 14, 2018 at 09:11:02AM -0600, Eric Blake wrote: [NBD and keepalive] > This is more food for thought on whether it even makes sense for NBD to > worry about assisting in keepalive matters, or whether it would just be > bloating the protocol. I'm currently leaning towards the latter. I don't think it makes (much) sense to run NBD over an unreliable transport. It uses TCP specifically to not have to worry about that, under the expectation that it won't break except in unusual circumstances; if you break that expectation, I think it's not unfair to say "well, then you get to keep both pieces". We already set the SO_KEEPALIVE socket option (at least nbd-server does; don't know about qemu) to make the kernel send out TCP-level keepalive probes. This happens only after two hours (by default), but it's something you can configure on your system if you need it to be lower. Having said that, I can always be convinced otherwise by good arguments :-) -- Could you people please use IRC like normal people?!? -- Amaya Rodrigo Sastre, trying to quiet down the buzz in the DebConf 2008 Hacklab