Date: Tue, 03 Aug 1999 18:56:31 -0700 From: Kent Stewart <kstewart@3-cities.com> To: Mark Ovens <markov@globalnet.co.uk> Cc: Greg Lehey <grog@lemis.com>, Bill Hussey <vfrboy@home.net>, questions@FreeBSD.ORG Subject: Re: Can't build kernel (was: Yo Quiero vnode_if.h) Message-ID: <37A79DCF.66F1B5F8@3-cities.com> References: <37A68550.EE8B3BF@home.net> <19990803154935.U62948@freebie.lemis.com> <19990803100618.B267@marder-1> <37A6F9D9.8350DB07@3-cities.com> <19990804004944.A269@marder-1>
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Mark Ovens wrote: > > On Tue, Aug 03, 1999 at 07:16:57AM -0700, Kent Stewart wrote: > > > Mark Ovens wrote: > > > > > On Tue, Aug 03, 1999 at 03:49:35PM +0930, Greg Lehey wrote: > > > > > > > On Tuesday, 3 August 1999 at 1:59:45 -0400, Bill Hussey wrote: > > > > > > > > > and as I read it in the book, there is no way to format an IDE > > > > > drive except, as the book puts it, to format it with the BIOS. > > > > > What does this mean? > > > > > > > > When you boot up some machines, the BIOS setup screens include > > > > a hard disk format utility. You can use this to format (in > > > > Microsoft terms: low-level format) an IDE disk. I'm pretty sure > > > > that's not necessary. > > > > > > > > > and totally pointless. AFAIK, (modern) IDE drives can only be > > > "low-level" formatted by the manufacturer. Using a BIOS format > > > utility will only succeed in trashing the servo info on the disk > > > thereby rendering the disk useless. Most (all?) IDE drives protect > > > themselves against these BIOS programs by simply sending back an > > > "OK" message, but without actually doing anything. > > > > Very true. I do not have an active system with a BIOS that will LLF > > an IDE drive. None of my Pentium's will but my last 486 system's > > BIOS would do a LLF. Drives have changed since then. However, you > > don't have to send the drive to the Manufacturer to get a low level > > format. They all have tools for THEIR drives. Some will even > > tell you when you need to obtain an RMA and return the drive for > > service. You only low level format when the drive has been handled > > very badly. This usually means a power hit in the process of writing > > to the disk. > > I would have thought that a power cut whilst writing to disk would > only affect the file-system (especially FAT, I've been there - > scrambled FATs). Bad handling, i.e. dropping them, would require > a LLF on older drives. Where I have seen it is when a spike comes along. Windows 95 seemed to be very sensitive to zapping a disk. > > I think I'm correct in saying that older IDE drives relied on the > head mechanism to position the heads where the tracks are *supposed* > to be, but if the drive was dropped, for example, then the heads > could become mis-aligned (and also with wear due to age) and would > then not align correctly, even trying to read/write 2 adjacent > tracks simultaneously. In this situation a LLF would write new > tracks onto the platters, which would then obviously align with > the heads. > > Later designs use servo tracking to dynamically align the heads > by having servo data written on the platters (next to the data > tracks?) which the head control mechanism uses to find the location > of the tracks. This means that the heads will always be aligned > with the tracks even if the drive has been dropped heavily (assuming > the heads don't touch the platters) or is old and worn. Also, with > the ever increasing track density the change in temperature as the > drive warms up would be sufficient to mis-algin the heads without > dynamic tracking. Unless the manufacturing has changed recently, the drive heads still float on a thin boundary layer of air. The media has changed and become more stable but you can still bounce the head into the media. Western digital has developed some laser bumps that keep the head up higher and prevent wear. They also move the head ever so often when the disk has become idle for something like 15 minutes and 5 seconds to prevent wear. It has been awhile since I have read about some of this but it made interesting reading at the time. Kent > > -- > FreeBSD - The Power To Serve http://www.freebsd.org > My Webpage http://www.users.globalnet.co.uk/~markov > _______________________________________________________________ > Mark Ovens, CNC Apps Engineer, Radan Computational Ltd. Bath UK > CAD/CAM solutions for Sheetmetal Working Industry > mailto:markov@globalnet.co.uk http://www.radan.com -- Kent Stewart Richland, WA mailto:kstewart@3-cities.com http://www.3-cities.com/~kstewart/index.html SETI(Search for Extraterrestrial Intelligence) @ HOME http://setiathome.ssl.berkeley.edu/ Hunting Archibald Stewart, b 1802 in Ballymena, Antrim Co., NIR http://www.3-cities.com/~kstewart/genealogy/archibald_stewart.html To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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