How to copy partition with trimming?

Question

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?

Answer 1

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.