#!/bin/bash
#
DIR="$1"        # The source of the millions of files
TARDEST="$2"    # Where the tarballs should be placed

# Create the million-file segments
rm -f /tmp/chunk.*
find "$DIR" -type f | split -l 1000000 - /tmp/chunk.

# Create corresponding tarballs
for CHUNK in $(cd /tmp && echo chunk.*)
do
    test -f "$CHUNK" || continue

    echo "Creating tarball for chunk '$CHUNK'" >&2
    tar cTf "/tmp/$CHUNK" "$TARDEST/$CHUNK.tar"
    rm -f "/tmp/$CHUNK"
done

#!/bin/bash
ctr=0;
while readarray -n 1000000 -t asdf; do
  ctr=$((${ctr}+1));
  tar czf /destination/path/asdf.${ctr}.tgz "${asdf[@]}";
  # If you don't want compression, use this instead:
  #tar cf /destination/path/asdf.${ctr}.tar "${asdf[@]}";
done <(find /source/path -not -type d);

function something() {...}
find /source/path -not -type d
  | readarray -n 1000000 -t -C something asdf

find /source/path -not -type d -print0
  | parallel -j4 -d '' -N1000000 tar czf '/destination/path/thing_backup.{#}.tgz'

find /source/path -not -type d -print0
  | parallel -j4 -d '' -N1000000 --tmpdir /destination/path --files tar cz

find /source/path -not -type d -print0
  | xargs -P 4 -0 -L 1000000 bash -euc 'tar czf $(mktemp --suffix=".tgz" /destination/path/backup_XXX) "$@"'

tar c /source/path | split -b $((3*1024*1024*1024)) - /destination/path/thing.tar.

cat $(ls -1 /destination/path/thing.tar.* | sort) | tar x