https://github.com/delan/guardbuffer

buffers and outputs input in regular blocks
https://github.com/delan/guardbuffer

Last synced: about 1 month ago
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buffers and outputs input in regular blocks

• Host: GitHub
• URL: https://github.com/delan/guardbuffer
• Owner: delan
• License: isc
• Created: 2013-06-01T10:55:16.000Z (over 11 years ago)
• Default Branch: master
• Last Pushed: 2016-01-23T17:46:54.000Z (almost 9 years ago)
• Last Synced: 2024-10-14T15:52:59.703Z (3 months ago)
• Language: C
• Size: 8.79 KB
• Stars: 0
• Watchers: 3
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE.txt

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README

        
GuardBuffer

===========

Buffers and outputs input in regular blocks.

Windows: copying raw partitions over a network

----------------------------------------------

To copy a partition on one computer to a file on another is simple. Let's assume

that 64 KiB is a 'sweet spot' block size where performance is maximised.

	dd bs=65536 if=\\?\Device\HarddiskX\PartitionY of=\\dest\path\file

Great, but copying directly from partition to partition is trickier. Very few

programs, `dd` included, support interacting with block device files and they

cannot be accessed over a network via sharing.

A potential solution, with the first command run on the source, and the other

on the destination:

	dd bs=65536 if=\\?\Device\HarddiskVolumeA | ncat -l 65432 --send-only

	ncat source 65432 --recv-only | dd bs=65536 of=\\?\Device\Hard...B

Strangely, the second `dd` isn't patient enough to wait for a full 64 KiB block,

and ends up attempting to write partial blocks. On Windows, writes to block

devices that are not a multiple of the sector size fail. This causes `dd` to

retry writing the partial blocks, padded with zeros, resulting in corruption.

The solution is simple, a buffer is needed to ensure that `dd` only ever

receives data in chunks of the block size, regardless of how they arrive from

the network.

	dd bs=65536 if=\\?\Device\HarddiskVolumeA | ncat -l 65432 --send-only

	ncat source 65432 --recv-only | gb | dd bs=65536 of=\\?\Device\Hard...B

In addition to this, `gb` also provides indications of time, progress and speed.