On Sunday 04 January 2009 17:30:52 Theodore Tso wrote: > On Sun, Jan 04, 2009 at 11:40:52PM +0100, Pavel Machek wrote: > > Not neccessarily. > > > > If I have a bit of precious data and lot of junk on the card, I want > > to copy out the precious data before the card dies. Reading the whole > > media may just take too long. > > > > That's probably very true for rotating harddrives after headcrash... > > For a small amount data, maybe; but the number of seeks is often far > more destructive than the amount of time the disk is spinning. And in > practice, what generally happens is the user starts looking around to > make sure there wasn't anything else on the disk worth saving, and now > data is getting copied off based on human reaction time. So that's > why I normally advise users that doing a full image copy of the disk > is much better than, say, "cp -r /home/luser /backup", or cd'ing > around a filesystem hierarchy and trying to save files one by one. That would be true if the disk hardware wasn't doing a gazillion retries to read a bad sector internally (taking 5 seconds to come back and report failure), and then the darn scsi layer added another gazillion retries on top of that, and the two multiply together to make it so slow that that when you leave the thing copying the disk overnight it's STILL not done 24 hours later. Going in and cherry picking individual files looks kind of appealing in that situation. Rob P.S. Yeah, I had a laptop hard drive crash a month or so back. I remember when it was still possible to buy storage devices that didn't get arbitrarily routed through the SCSI layer. I miss those days. I found the patch to route ramdisks through the scsi layer amusing, though. -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
