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On Wed, 2012-08-08 at 14:02 +1000, Adam Carter wrote: |
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> > I have seen where people use dd to do this sort of thing to. I read |
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> > somewhere that if you do a dd and put in all 1's, then all 0's then back |
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> > again that it is very hard to get any data back off the drive. I think |
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> > if you do it like over a dozen times, it is deemed impossible to get |
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> > anything back. I think that is the Government standard of it's gone. |
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> |
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> I've heard the old attacks to recover data from a zerod drive are no |
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> longer viable for disks of greater capacity than about 10G. I haven't |
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> seen the information myself, however. |
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> |
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> A single pass using dd would probably a good way of detecting any |
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> existing bad blocks, so a smartctl then dd then smartctl again and a |
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> diff of the results may be interesting. |
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> |
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> I just use a 1TB software mirror for my backups. |
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> |
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To wipe a drive use dban. - live CD which uses (US) gov approved |
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standards of wipe methods/patterns. |
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dd is only going to show sectors on a failed drive - too late! |
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To explain, modern drives have a store of locations they can use to |
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transparently replace any failed locations (apparently similar to the |
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way SSD's do it) - the internal drive electronics handle this and its |
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not visible externally though smart data seems to show it, but as google |
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says, smart is a bit suspect. The problem of a bad sector will only |
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show once all the reserved locations are used up, by which time the |
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drive is usually in rampant failure. |
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I do suspect this is one reason for googles results - actual failures of |
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the media (as against the motors/electronics are much as they always |
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have been, but the drives are not reporting them until its too late. |
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