Generate quickly 20GB of random data using openssl

20GB_random.sh

#!/usr/bin/env bash

# Generate 20GB file of random data in /dev/shm (~ramdisk)
time openssl enc -aes-256-ctr \
                 -pass pass:"$(dd if=/dev/urandom bs=128 count=1 2>/dev/null | base64)" \
                 -nosalt < /dev/zero 2>/dev/null | 
  dd bs=4M \
     count=5120 \
     status=progress \
     iflag=fullblock \
     of=/dev/shm/my_random_file

In a 6C/12T VM in Azure, 112GB RAM:

21466447872 bytes (21 GB) copied, 41.145581 s, 522 MB/s
5120+0 records in
5120+0 records out
21474836480 bytes (21 GB) copied, 41.1589 s, 522 MB/s

real	0m42.732s
user	0m12.757s
sys	0m57.393s

$ ls -lh /dev/shm/my_random_file 
-rw-rw-rw- 1 me me 20G Dec 14 13:22 /dev/shm/my_random_file