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I want to clopy a partition between SSD devices. Normally I could do it simply with the "dd" or "buffer" commands.

However, now that I have SSDs, I also would like to miss the unneeded writes.

I want all all-zero blocks handled as trimmed blocks.

Is there, ideally a command line tool, to do that?

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You can do this in two steps:

  • discard the contents of the target device (so that reads return zero):

    blkdiscard /dev/sdT1

  • copy the data, skipping instead of writing zero blocks (using GNU dd):

    dd bs=100M iflag=fullblock conv=sparse if=/dev/sdS1 of=/dev/sdT1

replacing S1 (source) and T1 (target) as appropriate.

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  • what's the significance of the magic number 100M ? Commented Oct 24 at 2:54
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    @jhnc nothing special, it’s supposed to be large enough to avoid inefficient reads/writes. Given modern SSD layouts it might be better as a power of two. Commented Oct 24 at 9:47

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