From owner-freebsd-scsi@FreeBSD.ORG Thu Feb 16 22:37:45 2006 Return-Path: X-Original-To: scsi@freebsd.org Delivered-To: freebsd-scsi@FreeBSD.ORG Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 6E1BF16A420 for ; Thu, 16 Feb 2006 22:37:45 +0000 (GMT) (envelope-from joao.barros@gmail.com) Received: from xproxy.gmail.com (xproxy.gmail.com [66.249.82.201]) by mx1.FreeBSD.org (Postfix) with ESMTP id EACB743D53 for ; Thu, 16 Feb 2006 22:37:43 +0000 (GMT) (envelope-from joao.barros@gmail.com) Received: by xproxy.gmail.com with SMTP id i26so211559wxd for ; Thu, 16 Feb 2006 14:37:43 -0800 (PST) DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=beta; d=gmail.com; h=received:message-id:date:from:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; b=KcQh+L9agFOF45GKQJZyk3LumCQqE5cMCe47/HA9OASy7fhIr/ybryDpvSW1TH92z7YZtAVyGKs4M77LsKzFoUTEqSvfW0yI/cjALm7kOvGOd976LTp07ynFLdi+NDnn+azFQwYbfVLQ4UxXozwl+y8tSH/yqgwwU3pkN9oVAmc= Received: by 10.70.48.16 with SMTP id v16mr240119wxv; Thu, 16 Feb 2006 14:37:43 -0800 (PST) Received: by 10.70.9.9 with HTTP; Thu, 16 Feb 2006 14:37:43 -0800 (PST) Message-ID: <70e8236f0602161437o1593c147na97239cf9054610e@mail.gmail.com> Date: Thu, 16 Feb 2006 22:37:43 +0000 From: Joao Barros To: Tom Samplonius In-Reply-To: <20060214103146.K99735@mgmt.uniserve.ca> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Content-Disposition: inline References: <2CEE6163475607F32A420FA1@jordgubbe.pingpong.net> <20060207121257.D53605@mgmt.uniserve.ca> <20060214150845.GB29569@in-addr.com> <20060214103146.K99735@mgmt.uniserve.ca> Cc: Palle Girgensohn , scsi@freebsd.org Subject: Re: NAS w/ multipath X-BeenThere: freebsd-scsi@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: SCSI subsystem List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 16 Feb 2006 22:37:45 -0000 On 2/14/06, Tom Samplonius wrote: > > On Tue, 14 Feb 2006, Gary Palmer wrote: > > > I suspect higher end devices (e.g. HDS and EMC Symmetrix units) this > > isn't a problem, but in mid range and lower end stuff I'd expect proble= ms > > if the paths landed on separate controllers on the array. > > I don't think this is a problem with current mid-range stuff. A mirro= red > write cache is considered a basic feature. Not only does a mirrored writ= e cache > protect against controller cache consistancy, it also protects losing the > contents of the write cache if a controller fails, which is generally a m= uch > bigger problem. The EMC Clarion Series, at least the CX600 model I work with has mirrored write cache. In the event of controller failure it is disabled until redundancy is resto= red. I had training on an entry level model, a CX300 and the funcionality was the same. The Symetrix I bet it has but EMC doesn't let us touch those ;-) -- Joao Barros