Date: Thu, 05 Mar 1998 08:06:50 -0000 (GMT) From: Duncan Barclay <dmlb@ragnet.demon.co.uk> To: Simon Shapiro <shimon@simon-shapiro.org> Cc: hackers@FreeBSD.ORG, julian@whistle.com, Wilko Bulte <wilko@yedi.iaf.nl> Subject: Re: SCSI Bus redundancy... Message-ID: <XFMail.980305080650.dmlb@computer.my.domain> In-Reply-To: <XFMail.980304152804.shimon@simon-shapiro.org>
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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
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