Date: Wed, 14 Oct 1998 09:43:32 -0400 (EDT) From: Bill Vermillion <bill@bilver.magicnet.net> To: freebsd-isp@FreeBSD.ORG Subject: Re: filesystem safety and SCSI disk write caching Message-ID: <199810141343.JAA10165@bilver.magicnet.net> In-Reply-To: <199810140608.AAA16953@pluto.plutotech.com> from "Justin T. Gibbs" at "Oct 14, 98 00:01:53 am"
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Justin T. Gibbs recently said: > >} The drive will reinitialize to the 'power on state' if the > >} power fluctuates into a zone that might invalidate it's > >} run-time state. It doesn't take a very long spike for the > >} drive's power-glitch sensor to go off. In this case, dropping > >} cached contents on the floor is much safer than attempting to > >} continue from an unknown state. > >If that's the reason for the problem that I saw, then the UPS the > >system was plugged into wasn't sufficient to prevent the problem. > Why is that? Do you have gremlins walking around hitting the reset > buttons on your machines? The UPS should isolate the machine from > any drop in power that would cause it to lose its brain other than > that caused by a hardware failure or an administrator hitting the > reset or power switch. All UPSes (UPSii) are not alike. The industrial units have some pretty severe power conditioning. At one time there was a distinction between a UPS and a Battery Backup - the latter only being a switch over circuit. High end units will ensure a constant exact power output, highly filtered and reliable. The best of them actually run the systems off of a converted AC to DC - so they appear - electrically at least - to be running from a battery - a device which has no spikes, and a very even output. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-isp" in the body of the message
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