From owner-freebsd-isp Wed Oct 14 06:41:34 1998 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id GAA24316 for freebsd-isp-outgoing; Wed, 14 Oct 1998 06:41:34 -0700 (PDT) (envelope-from owner-freebsd-isp@FreeBSD.ORG) Received: from magicnet.magicnet.net (magicnet.magicnet.net [204.96.116.9]) by hub.freebsd.org (8.8.8/8.8.8) with ESMTP id GAA24311 for ; Wed, 14 Oct 1998 06:41:33 -0700 (PDT) (envelope-from bill@bilver.magicnet.net) Received: (from uucp@localhost) by magicnet.magicnet.net (8.8.6/8.8.8) with UUCP id JAA09179 for freebsd-isp@freebsd.org; Wed, 14 Oct 1998 09:39:30 -0400 (EDT) Received: (from bill@localhost) by bilver.magicnet.net (8.9.1/8.9.1) id JAA10165 for freebsd-isp@freebsd.org; Wed, 14 Oct 1998 09:43:32 -0400 (EDT) From: Bill Vermillion Message-Id: <199810141343.JAA10165@bilver.magicnet.net> Subject: Re: filesystem safety and SCSI disk write caching In-Reply-To: <199810140608.AAA16953@pluto.plutotech.com> from "Justin T. Gibbs" at "Oct 14, 98 00:01:53 am" To: freebsd-isp@FreeBSD.ORG Date: Wed, 14 Oct 1998 09:43:32 -0400 (EDT) X-Mailer: ELM [version 2.4ME+ PL38 (25)] MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-freebsd-isp@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.org 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