Testing disk write speed on embedded Linux devices (WARNING! USE WITH CARE! As it might overwrite your system partitions )

gistfile1.txt

#!/bin/bash

# This script copies data synchronously from one block device to a second one.
#
# It will perform the same operation using multiple block sizes, which makes
# it easy to find the optimal one for the current device and configuration.
#
# WARNING!
#
# This will blindly write data to a partition and if not used with care, it
# has the possibility overwrite your system partitions!

set -e

# Clear PageCache, dentries and inodes.
function drop_cache() {
  sync; echo 3 > /proc/sys/vm/drop_caches
}

INPUT_FILE=$1
OUTPUT_FILE=$2

if [ ! -b ${INPUT_FILE} ] || [ ! -b ${OUTPUT_FILE} ] \
    || [ -z "${INPUT_FILE}" ] || [ -z "${OUTPUT_FILE}" ]; then
  echo "You must specify block devices as arguments...."
  echo ""
  echo "Usage:"
  echo "    ./write-speed-test.sh /dev/mmcblk0p2 /dev/mmcblk0p3"
  exit 1
fi

INPUT_FILE_SIZE=$(blockdev --getsize64 ${INPUT_FILE})
OUTPUT_FILE_SIZE=$(blockdev --getsize64 ${OUTPUT_FILE})

if [ ${INPUT_FILE_SIZE} -ne ${OUTPUT_FILE_SIZE} ]; then
  echo "The input and target block device size do not match"
  echo "Input size: ${INPUT_FILE_SIZE}"
  echo "Input size: ${OUTPUT_FILE_SIZE}"
  exit 1
fi

echo "Block size: $(( ${INPUT_FILE_SIZE} / 1024 / 1024 )) MiB (${INPUT_FILE_SIZE})"

#sizes=(512 1KiB 4KiB 8KiB 16KiB 32KiB 64KiB 512KiB 1MiB 4MiB 8Mib)
sizes=(1KiB 4KiB 8KiB 16KiB 32KiB 64KiB 128KiB 256KiB 512KiB 1MiB 4MiB 8MiB)
for size in "${sizes[@]}"; do
  echo ""
  echo "************************************************************"
  echo "Testing with ${size} block size"
  drop_cache
  time dd if=${INPUT_FILE} of=${OUTPUT_FILE} bs=${size} oflag=dsync
  echo "************************************************************"
  echo ""
done