[gentoo-user] Re: Fast checksumming of whole partitions

[7v5w7go9ub0o <7v5w7go9ub0o@gmail.com>]

On 06/05/10 02:39, meino.cramer@gmx.de wrote:
[]
>
> Is there any faster and reliable way to checksum whole paritions (not
> on "per file" base)???


FWIW, portage has a tool called "dcfldd" that works well for me. It is
dd with the addition of:

      *   Hashing on-the-fly - dcfldd can hash the input data as it is
being transferred, helping to ensure data integrity.
      * Status output - dcfldd can update the user of its progress in
terms of the amount of data transferred and how much longer operation
will take.
      * Flexible disk wipes - dcfldd can be used to wipe disks quickly and
with a known pattern if desired.
      * Image/wipe Verify - dcfldd can verify that a target drive is a
bit-for-bit match of the specified input file or pattern.
      * Multiple outputs - dcfldd can output to multiple files or disks at
the same time.
      * Split output - dcfldd can split output to multiple files with more
configurability than the split command.
      * Piped output and logs - dcfldd can send all its log data and
output to commands as well as files natively.


e.g. when I copy my HD, I get a copy status report and hash by using the
following commands:

#!/bin/bash
dcfldd if=/dev/sda bs=4096k sizeprobe=if status=on hashwindow=0 of=/dev/sdb
dcfldd if=/dev/sdb bs=4096k sizeprobe=if status=on hashwindow=0 of=/dev/null

When they've completed, I'll visually compare the two hashes (you can
automate this.) You can get fancier and do the Verify instead of the hashes.

HTH

(p.s.  Part of your answer is setting the best blocksize for dd or
dcfldd.

I'd presume it the smaller of your available memory, or the buffer size
on your HD?...... someone please correct me on this!?)