At 03:42 PM -0800 02/06/2003, Terry Graham wrote: >Is the bad data more likely to be directory and system-related >and if so is it repairable by the likes of TT Pro 3 and Disk Warrior etc., >or can it happen in any files?
(simplified) The first thing the MacOS does, when accessing a drive, is read its partition map. Then it loads the full driver (which Apple stashes in a special partition). Then it accesses the file system's data (HFS/HFS+ directory structures) from the boot partition. Then it creates a small file on the boot partition (the existance of this file is how the system knows it crashed when next you boot). Then it continues with the boot process. If the packets on the SCSI are being corrupted, the read operations just get repeated until they work (more or less). But the write can damage things. Murphy's law says it will be the directory write operation and not the actual file data write that's damaged. :\ At that point, the disk is usually repairable if you use Disk First Aid or another such tool on it. But the longer you wait (the more writing you do) the worse the problem gets... >I got a little casual cause I've been popping drives in and out of the center >bay of my 660 to ready them for give-away 68K machines - the ID Jumpers >on those under-200MB drives are easy to understand by comparison to this >Micropolis. What's the full model number of the Micropolis? Perhaps we can find you some detailed/better info. >But how I've been getting away with no conscious "termination" >re. my Centris 660AV center bay, is now a new mystery. Termination is needed to prevent signals from "echoing" off the end of the cable. It's the echos overlapping that cause the corruptions. Sometimes, when cables are short and data rates are slow, such as on an internal SCSI-1 bus, the echo is minimal so things just hum along fine. SCSI-2 isn't that tolerant tho... - Dan. -- PCI-PowerMacs is sponsored by <http://lowendmac.com/> and... Small Dog Electronics http://www.smalldog.com | Refurbished Drives | -- Sonnet & PowerLogix Upgrades - start at $169 | & CDRWs on Sale! | Support Low End Mac <http://lowendmac.com/lists/support.html> PCI-PowerMacs list info: <http://lowendmac.com/lists/pci-powermacs.shtml> --> AOL users, remove "mailto:"; Send list messages to: <mailto:[EMAIL PROTECTED]> To unsubscribe, email: <mailto:[EMAIL PROTECTED]> For digest mode, email: <mailto:[EMAIL PROTECTED]> Subscription questions: <mailto:[EMAIL PROTECTED]> Archive:<http://www.mail-archive.com/pci-powermacs%40mail.maclaunch.com/> Using a Mac? Free email & more at Applelinks! http://www.applelinks.com
