From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Thu, 3 May 2001 15:58:46 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Thu, 3 May 2001 15:58:31 -0400 Received: from pyongsan.compgen.com ([158.155.0.1]:54540 "EHLO panmunjom.compgen.com") by vger.kernel.org with ESMTP id ; Thu, 3 May 2001 15:58:09 -0400 From: "Eric Z. Ayers" MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-ID: <15089.47157.268005.262050@gargle.gargle.HOWL> Date: Thu, 3 May 2001 15:57:41 -0400 (EDT) To: Pavel Machek Cc: Doug Ledford , Max TenEyck Woodbury , Eric.Ayers@intec-telecom-systems.com, James Bottomley , "Roets, Chris" , linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org Subject: Re: Linux Cluster using shared scsi In-Reply-To: <20010502230357.A9507@bug.ucw.cz> In-Reply-To: <200105011445.KAA01117@localhost.localdomain> <3AEEDFFC.409D8271@redhat.com> <15086.60620.745722.345084@gargle.gargle.HOWL> <3AF025AE.511064F3@redhat.com> <3AF04648.73F5BFCE@cds.duke.edu> <3AF0483C.49C8CF90@redhat.com> <20010502230357.A9507@bug.ucw.cz> X-Mailer: VM 6.72 under 21.1 (patch 8) "Bryce Canyon" XEmacs Lucid Reply-To: Eric.Ayers@intec-telecom-systems.com X-Face: (3Y\Z;G!Ce[Q\WBgGFLgcaL%v[kJ'@9s`Qn1<)EEL5tSW7IDvX[{APQ5]eY}uF}%qbD[-@N !5]S!%o0*DbAB?~o%tca^?3@zU~"fQ@MTiClP>w%`Y8oG&6|:>2F=bhnf2>bPedqw-.T>U-BaI`F>1 QY@?oGJ0.lV?b@0HgvaOt>=0,/@,=(kE"J++vO?K"3ve@,"sunF0HnU|h&|:}%|P6%BohO_*mAHJ#g EHc;_'bXG|kCLMSF`:/O_F0fuJ:j2^C\NJ(:$izN@mbXQo(IL,BO.7<]wT?:5.A<$C Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Pavel Machek writes: > Hi! > > > > > ... > > > > > > > > If told to hold a reservation, then resend your reservation request once every > > > > 2 seconds (this actually has very minimal CPU/BUS usage and isn't as big a > > > > deal as requesting a reservation every 2 seconds might sound). The first time > > > > the reservation is refused, consider the reservation stolen by another machine > > > > and exit (or optionally, reboot). > > > > > > Umm. Reboot? What do you think this is? Windoze? > > > > It's the *only* way to guarantee that the drive is never touched by more than > > one machine at a time (notice, I've not been talking about a shared use drive, > > only one machine in the cluster "owns" the drive at a time, and it isn't for > > single transactions that it owns the drive, it owns the drive for as long as > > it is alive, this is a limitation of the filesystes currently available in > > mainstream kernels). The reservation conflict and subsequent reboot also > > *only* happens when a reservation has been forcefully stolen from a > >machine. > > I do not believe reboot from kernel is right approach. Tell init with > special signal, maybe; but do not reboot forcefully. This is policy; > doing reboot might be right answer in 90% cases; that does not mean > you should do it always. ... However distateful it sounds, there is precedent for the behavior that Doug is proposing in commercial clustering implementations. My recollection is that both Compaq TruCluster and HP Service Guard have logic that will panic the kernel when a disk is "stolen" from under a running service and there is a "network partition" in the cluster. A network partition occurs when multiple machines in the cluster are runnig, but the HA software agents on two nodes can't communicate via the network to arbitrate which node should be the owner of the disk. -Eric -- Eric Z. Ayers Lead Software Engineer Phone: +1 404-705-2864 Computer Generation, Incorporated Fax: +1 404-705-2805 an Intec Telecom Systems Company Web: http://www.intec-telecom-systems.com/ Email: eric.ayers@intec-telecom-systems.com Postal: Bldg G 4th Floor, 5775 Peachtree-Dunwoody Rd, Atlanta, GA 30342 USA