In reply to: Shawn Mulligan, 19 Nov 2002: Hi Shawn, Thanks for your reply!
> All data tracks except for Mode 2/2536 or something > have at least some sort of error correction, usually > both a CRC and ECC (like checksum). Errors are always > detectable, and sometimes even recoverable, especially > in Mode 1/2048 (there's like 512 bytes of error > correction data for every 2048 bytes of data). So at > the very least, you'd know when you tried to restore > that something was wrong, because the file would not > copy over, or would give you an error. That's good to know. It appears that I had the wrong idea about how CD-R's handle errors. Sounds like maybe there isn't as much to worry about, as I had initially thought, at least as far as knowing whether or not a particular file had any errors. (I don't know what Mode my burner uses, though) > If Disk Copy is actually doing a Checksum instead of > a CRC, it actually has less error correction in it's > image than the CD, because it can't usually repair > the error, only detect it. I guess I didn't know they were two different things, but the Finder's "Get Info" window for one of these (unmounted) disk image files shows the following info: CRC: $012F4560 All of them show that "CRC: $" thing followed by other various other numbers and letters. > Of course, any error correction used in a Disk Copy > image is going to be on top of what's already on the > CD, so you WILL get a little more error detection > ability. Sounds reasonable. > BTW, if you just keep your backup CD-R's out of > sunlight and humidity, they will probably last well > beyond their rated lifespan. Yeah, I'd thought so too, until I had those 2 disks that wouldn't even read at all - got me sort of paranoid. They had been stored exactly to manufacturer recommendations for archival storage, temp/humidity/ light /no-labels/no-bending/no-scratching/no-touching/ /no-writing-on/the whole 9 yards, and as with most of the others had only been out of their jewel cases just once or twice, so I don't what their problem was. Just luck of the draw, maybe. The other disks in that same lot number, and storage, were fine. You're probably right about the majority of CD-R's, though - I suppose a couple of failed disks here and there don't constitute a major catastrophe, percentage-wise that is. I'll just make sure to keep doing the duplicates thing, though, just in case. I very much appreciate all the good info, and thanks again for the reply, - Jamie marie . __________________________________________________ Do you Yahoo!? Yahoo! Web Hosting - Let the expert host your site http://webhosting.yahoo.com -- 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/> --------------------------------------------------------------- >The Think Different Store http://www.ThinkDifferentStore.com ---------------------------------------------------------------
