Date: Tue, 3 Mar 1998 15:51:20 -0600 From: Karl Denninger <karl@mcs.net> To: Julian Elischer <julian@whistle.com> Cc: shimon@simon-shapiro.org, hackers@FreeBSD.ORG Subject: Re: SCSI Bus redundancy... Message-ID: <19980303155120.43579@mcs.net> In-Reply-To: <34FC66A3.2781E494@whistle.com>; from Julian Elischer on Tue, Mar 03, 1998 at 12:22:59PM -0800 References: <XFMail.980303121451.shimon@simon-shapiro.org> <34FC66A3.2781E494@whistle.com>
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On Tue, Mar 03, 1998 at 12:22:59PM -0800, Julian Elischer wrote: > Simon Shapiro wrote: > > > > I have seen an interesting solution some time ago; Instead of battery, the > > spindle motor (on the disk) was used to generate the power needed to flush > > the caches. then the motor leads will be clamped, and the spidle shut down > > quickly (normal procedure nowdays). This was done on a 14" spindle that > > had a bit more inertia than todays' disks. But the circuitry consumed more > > power too. > > > > spindle inertia is no longer used for power. > > I quote from the Qantum fireball programmer's manual.. > > "You may apply the power in any order, or open either the power or > return line with no loss of data or damage to the disk drive. However, > data may be lost in the sector being written at the time of power > loss." > > Other drives have similar stories to tell. > > We queried the manufacturers closely on this > and they confirmed that they cease all operation IMMEDIATLY on > recognition of power loss. > > julian It is extremely dangerous to attempt to continue operating with unknown power levels on a winchester disk. In the extreme you could damage the format, rendering the sector being written unusable. In days of old, you could cause a headcrash (nowdays the voicecoil positioners retract on power loss) :-) You want the heads off the active media surface and the write gate off *now* if you detect a power failure. -- -- Karl Denninger (karl@MCS.Net)| MCSNet - Serving Chicagoland and Wisconsin http://www.mcs.net/ | T1's from $600 monthly to FULL DS-3 Service | NEW! K56Flex support on ALL modems Voice: [+1 312 803-MCS1 x219]| EXCLUSIVE NEW FEATURE ON ALL PERSONAL ACCOUNTS Fax: [+1 312 803-4929] | *SPAMBLOCK* Technology now included at no cost To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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