From owner-freebsd-net@FreeBSD.ORG Mon Mar 13 13:16:13 2006 Return-Path: X-Original-To: freebsd-net@freebsd.org Delivered-To: freebsd-net@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 5E7C016A41F for ; Mon, 13 Mar 2006 13:16:13 +0000 (UTC) (envelope-from cswiger@mac.com) Received: from pi.codefab.com (pi.codefab.com [199.103.21.227]) by mx1.FreeBSD.org (Postfix) with ESMTP id AE4DC43D45 for ; Mon, 13 Mar 2006 13:16:12 +0000 (GMT) (envelope-from cswiger@mac.com) Received: from localhost (localhost [127.0.0.1]) by pi.codefab.com (Postfix) with ESMTP id CD4D15D00; Mon, 13 Mar 2006 08:16:11 -0500 (EST) Received: from pi.codefab.com ([127.0.0.1]) by localhost (pi.codefab.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 54697-02; Mon, 13 Mar 2006 08:16:10 -0500 (EST) Received: from [192.168.1.3] (pool-68-161-129-91.ny325.east.verizon.net [68.161.129.91]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by pi.codefab.com (Postfix) with ESMTP id 5A79E5C28; Mon, 13 Mar 2006 08:16:10 -0500 (EST) Message-ID: <4415709D.4070203@mac.com> Date: Mon, 13 Mar 2006 08:16:13 -0500 From: Chuck Swiger Organization: The Courts of Chaos User-Agent: Thunderbird 1.5 (Windows/20051201) MIME-Version: 1.0 To: Nikolas Britton References: In-Reply-To: X-Enigmail-Version: 0.94.0.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-Virus-Scanned: amavisd-new at codefab.com Cc: freebsd-net@freebsd.org Subject: Re: floating a server room... how do you deal with ethernet connections? X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 13 Mar 2006 13:16:13 -0000 Nikolas Britton wrote: > I'm currently planning renovations for the power mains supplying are > server room. One of the ideas I have is to float the entire room using > a isolation transformer. Umph, that's normally only needed if you are seeing extreme line noise or have other serious problems with the building mains supply like a poor or faulty building ground. If you do have building grounding problems, then using an isolation transformer will probably help your equipment but the problem should still be fixed elsewhere. > The only problem to this solution, that I can > think of, is that all of the equipment that's attached to the other > end of the Ethernet cabling won't be isolated, the NIC cards do have > 1:1 transformer coupling for the wire pairs but... In the event of > power surges, spikes, brownouts, and/or nearby lighting strikes I feel > that It's conceivable for there to be a large voltage differential on > the wires that could damage the equipment on ether end of the wire. Actually, you don't even need a lightning strike-- one can see 50 to 100V swings in relative voltages between neutral and the fusebox ground or neutral and a water pipe just by having the building ground fail. [1] Adding an isolation transformer to the mix won't hurt, but it won't help that much, either. If you want room-wide surge suppression at the breaker panel, get a TVSS or a 10kVA or larger UPS. Consider something like the Leviton 54000 or 57000: http://www.weberelectricsupply.com/57000.html http://www.leviton.com/sections/prodinfo/newprod/npleadin.htm ...which are rated for 3-phase "wye" 120/208V or 277/408V @ 100 amps per phase, and run about two grand. The other choice would be to hunt down a PowerWare or maybe an APC Symmetra UPS, which will run 20-30K. Note that the APC Symmetra cheats and doesn't provide galvanic isolation during normal operation, whereas the PowerWare runs the inverter continuously which is a bit less efficient, but gives cleaner power. These sorts of units ought to have a "DC servo offset circuit", if I'm remembering the details and phrase right, which will compensate for a constant voltage differential between neutral and ground. -- -Chuck [1]: Three guesses as to how I know this? :-)