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Re: Gutmann's research paper today
From: Frank Knobbe <frank () knobbe us>
Date: Tue, 07 Feb 2006 10:16:35 -0600

On Tue, 2006-02-07 at 10:07 -0500, Valdis.Kletnieks () vt edu wrote:
One place where "random scrubbing" falls down is the requirement to *verify*
that the blocks were written.  If you wrote a disk full of zeros, it's a
trivial matter to read it back and verify that all the bytes are zeros.  If you
wrote a whole disk of pseudo-random, then you have to regenerate the entire
pseudo-random data stream in order to compare it....

Shouldn't you be able to do that cluster by cluster? Grab 1024 or
random, write it, then read it and verify?

Alternatively, more stream based, you could dd /dev/random, tee that to
the drive and pipe the other stream into md5. Take note of the hash. At
the end, dd the drive into md5 and compare the resulting hash.

I'm performing backups where the stream is tee'ed to the drive and into
md5 for hash creation. Works great with tapes, should work for drives
too.

Cheers,
Frank

-- 
It is said that the Internet is a public utility. As such, it is best
compared to a sewer. A big, fat pipe with a bunch of crap sloshing
against your ports.

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