From owner-freebsd-hackers Thu Mar 5 10:13:57 1998 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id KAA22103 for freebsd-hackers-outgoing; Thu, 5 Mar 1998 10:13:57 -0800 (PST) (envelope-from owner-freebsd-hackers@FreeBSD.ORG) Received: from post.mail.demon.net (post-20.mail.demon.net [194.217.242.27]) by hub.freebsd.org (8.8.8/8.8.8) with SMTP id KAA21976 for ; Thu, 5 Mar 1998 10:13:17 -0800 (PST) (envelope-from dmlb@ragnet.demon.co.uk) Received: from ragnet.demon.co.uk ([158.152.46.40]) by post.mail.demon.net id aa2025315; 5 Mar 98 18:02 GMT Received: from dmlb by ragnet.demon.co.uk with local (Exim 1.73 #1) id 0yAVg3-0006iN-00; Thu, 5 Mar 1998 08:06:51 +0000 Message-ID: X-Mailer: XFMail 1.2 [p0] on FreeBSD X-Priority: 3 (Normal) Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 8bit MIME-Version: 1.0 In-Reply-To: Date: Thu, 05 Mar 1998 08:06:50 -0000 (GMT) From: Duncan Barclay To: Simon Shapiro Subject: Re: SCSI Bus redundancy... Cc: hackers@FreeBSD.ORG, julian@whistle.com, Wilko Bulte Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG On 04-Mar-98 Simon Shapiro wrote: > > On 04-Mar-98 Wilko Bulte wrote: > > ... > >> An extra power supply is money well spent. We ship all our standalone >> arrays at least with N+1, optional 2N power. 2N gives you 2 seperate >> power entry points to the power grid. Now we only need to educate people >> to use two different power branches (phases? what's the right English >> term?) > > The old DPT 9W tower (made by DEC) had an interesting feature, where the > power INPUT was switchable too. If the AC to one supply went dowm it will > draw AC from the other. > > Yes, 2N P/S is trivial to do (2 diods/circuit if I remember right) and > cheap. Technically, you want each supply fed from a different phase. In > the US they are referredto as ``independant circuits''. I have seen people > paying lots of money to get that, where they have 220V right in the same > room (220BAC in the US is 2-phases, 180 degrees apart, unlike the European > 3 phasees 120 degrees apart. Yest, you can get 3phase circuits in the US > too). The hot wire in a 220VAC, in the us is 117VAC to ground, 220VAC > hot-hot. > Are you sure you guys want to use different phases of a the same feed? Remember all two or three phases come into the building from the same sub-station down the same pice of cable. Most comman fault is a digger cutting this cable taking out all three phases or temp. shorts in the overheads to the sub-station (auto reset ater a couple of minutes; usually from wind blowing the cables together). You need feeds from seperate sub-stations. Duncan --- ________________________________________________________________________ Duncan Barclay | God smiles upon the little children, dmlb@ragnet.demon.co.uk | the alcoholics, and the permanently stoned. ________________________________________________________________________ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message