Calculating or verifying md5 checksums for lots of file always a time-consuming process. Here are some notes for how to work with md5 checksum via GNU parallel.
1. Install GNU parallel
sudo apt update sudo apt install parallel
2. Calaulate md5 checksum in batch
find /data -type f | parallel -j 64 md5sum > md5.txt
-joption indicates the maximum number of jobs that are run at the same time.
3. Verify md5 checksum in batch
cat md5.txt | parallel --pipe -N1 md5sum -c
-Nindicates use at most number of arguments per command line.
If files are small, use