On Mon, Oct 22, 2001 at 03:44:28AM +0000, Yuwen Dai wrote: > I have two identical hard disk linked with one cable. The capacity of each > disk is 40G. I want to have the second disk be the mirror of the first disk > by using this command: > > dd if=/dev/hda of=/dev/hdb bs=32k > > Nearly 2 hours passed, dd still hadn't finished. I had to press 'Ctrl-C' to > stop it. Is this the right way to mirror a disk? Or is there some better > way to do this? Thanks in advance. First of all, you'd probably be better off using dump and restore rather than dd. dd will copy a block even if it's completely unused by the filesystem. So if the drive you're backing up is only 25% full, then dd will take 4 times longer than dump, simply because it's copying a bunch of unnecessary blocks. Also, you're probably better off moving these drives to separate controllers. I don't remember all the details of it, but IDE has traditionally had a limitation that allowed a controller to only queue commands for a single drive at a time. Such a limitation would have a major impact on performance in a case like this. Unfortunately I can't provide you with a reference for this, and I don't know if it's still the case with modern IDE controllers. noah -- _______________________________________________________ | Web: http://web.morgul.net/~frodo/ | PGP Public Key: http://web.morgul.net/~frodo/mail.html
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