gistfile1.sh

#Solaris/cross platform stat
stat_sizes() { perl -e '$file=shift; @f=stat($file); printf("%s bytes made up of %s*%s blocks\n",$f[7],$f[12],$f[11]);' "$1"; }

# Run something until it returns 0
wait_until() {
  local cmd="$1"
  local time_start=$(date +%s)
  while ! $cmd; do
    sleep 1
  done
  local time_end=$(date +%s)
  printf "Waited %s seconds for [$cmd]\n" $(expr $time_end - $time_start)
}

# wait_until
compressratio_is_not_one() {
  zfs_get_compressratio | grep -vq '1.00x'
}

# wait_until
compressratio_is_one() {
  zfs_get_compressratio | grep -q '1.00x'
}

zfs_get_compressratio() {
  zfs get -Hp compressratio $ZFS_FS | awk '{ print $3}'
}

# Run with: test_compression file_system
# Assumes the zfs file system is mounted on /file_system
test_compression() {
  if [ -z "$1" ] || ! zfs list "$1" 2>&1 >/dev/null; then
    printf "zfs file system as argument [%s]" "$1"; return 0; fi 
  
  export ZFS_FS="$1"
  printf "Testing [%s]\n\n" "$ZFS_FS"
  cd /$ZFS_FS || return 0
  rm -f testfile*

  for i in 1 4 256 8096; do
    printf "Testing size [%s]\n" $(expr 4096 \* $i)
    wait_until compressratio_is_one
    dd if=/dev/zero bs=4k count=$i 2>/dev/null | tr "\000" "a" > testfile$i
    stat_sizes testfile$i
    wait_until compressratio_is_not_one
    zfs_get_compressratio
    echo
    rm testfile$i
  done
}