Date: Fri, 2 Mar 2001 21:51:30 -0800 From: "Ted Mittelstaedt" <tedm@toybox.placo.com> To: "Christopher Farley" <chris@northernbrewer.com>, "richard childers" <fscked@pacbell.net> Cc: "Artem Koutchine" <matrix@ipform.ru>, <freebsd-questions@FreeBSD.ORG> Subject: RE: Hot swap IDE device? Message-ID: <000701c0a3a5$fefd0520$1401a8c0@tedm.placo.com> In-Reply-To: <20010302173424.A5456@northernbrewer.com>
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The trick to all of these hot-swap deals is that for them to work, on the connector that plugs in the drive, the power and ground pins must be elongated in such a fashion as that they make positive solid contact before the data pins are connected. Otherwise if you apply power to data pins before the power supply rails you will damage the drive electronics. (this is why many SCSI cards use fuses, by the way) You can look for this by eye on any hot-plug thing you buy - if the power pins aren't longer than the rest, it's not hot plug. Of course, being able to hot-plug IDE doesen't necessairly mean that if you do it on a running system that once the drive is transitioned in, that the IDE bus is going to be in any shape to take commands, let alone the drive electronics. IDE devices need to be reset and initialized and the OS has no provisions for this. Also, you run the risk of introducing electronic garbage on the bus and corrupting any data being transferred to other IDE devices on the bus. If you really need hot-plugability you can do it with SCSI. The trick is simple, you put 2 SCSI cards in the computer. The first card has the boot drive on it along with the root partition. The second card is connected to an external drive or drives. As long as you unmount the external drives and stop them with camcontrol, it's safe to unplug them. If you then need to plug them back in, once you have the connector seated you send a scsi rescan command to the second SCSI card with camcontrol. Naturally, doing this disrupts all data flow on the SCSI bus on the second card. Ted Mittelstaedt tedm@toybox.placo.com Author of: The FreeBSD Corporate Networker's Guide Book website: http://www.freebsd-corp-net-guide.com >-----Original Message----- >From: owner-freebsd-questions@FreeBSD.ORG >[mailto:owner-freebsd-questions@FreeBSD.ORG]On Behalf Of Christopher >Farley >Sent: Friday, March 02, 2001 3:34 PM >To: richard childers >Cc: Artem Koutchine; freebsd-questions@FreeBSD.ORG >Subject: Re: Hot swap IDE device? > > >richard childers (fscked@pacbell.net) wrote: > >> That's a good question; what does your swappable IDE drive kit say about >> doing it while the power was on? I think Artem is right; won't work ... >> under IDE, at least. > >The documentation is very poor; it is only printed on the box, and it >appears to be a poor translation, ie: > > - In-tray box... with HOT-SW AP/PNP AND MULTI-PARTITIONING function, > without rebooting system on/off upgrade your PC in seconds. > > - WARNING: Please turn off the power of case or mobile rack > before removing your mobile rack > > >Despite the warnings, I installed this on some old hardware. FreeBSD >3.4 froze solid when I powered the drive down (without unmounting >the filesystem!), but everything came back to life when I restored >the power. > >On the second attempt, I unmounted the filesystem, and powered the drive >down. FreeBSD did not complain until I powered back up and tried to >remount the filesystem. > >That was the last I saw from my old 50 MB Conner HD. That thing was >pretty expensive back in 1993, too... > >-- >Christopher Farley >www.northernbrewer.com > >To Unsubscribe: send mail to majordomo@FreeBSD.org >with "unsubscribe freebsd-questions" in the body of the message > To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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