On Tue, 9 Dec 2003, perrin wrote:
> > Oh, I thought that by "image" you meant like Ghost makes under Windows, or
> > like "cat /dev/hda > file" would make. You meant duplicate the drive.
> > Right, that'll work. That's basically what I'm doing now.
>
> Last I checked, Ghost makes an exact duplicate that doesn't have any
> additional overhead on the destination media.
Surely it puts some signature bytes at the beginning or end. Otherwise it
just has the filename and your word to go on,
> I suppose I could be mistaken.
Well, if you have Ghost (I don't), you could test it...
> > Something must be wrong, though -- CPU use rises to ~50% during the copy.
> > Both drives use DMA, according to hdparm. I didn't think CPU was supposed
> > to be used during a DMA transfer.
>
> Copying uses processing power because the processor is making decisions to
> manage reading and writing. DMA only allows other devices to directly
> access data from the drives without having to go through the processor.
> Something still needs to control the drives, and if there aren't any
> additional devices doing so that task falls to the CPU.
What kind of devices would control an IDE hard drive? Would a SCSI hard
drive exhibit the same phenomenon?
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