demonstrate time to clone a ephemeral disk image

example-results

=== size=10G LABEL=ephemeral0 FSTYPE=ext3 ===
truncate          real: 0m0.053s user: 0m0.000s sys: 0m0.000s
mkfs.ext3         real: 0m8.295s user: 0m0.008s sys: 0m0.584s
cp working o      real: 0m0.284s user: 0m0.048s sys: 0m0.216s
cp working q      real: 0m0.162s user: 0m0.036s sys: 0m0.120s
rm working        real: 0m0.083s user: 0m0.000s sys: 0m0.080s
sync              real: 0m1.608s user: 0m0.000s sys: 0m0.000s
flush cache       real: 0m0.748s user: 0m0.004s sys: 0m0.032s
[1] cp new        real: 0m1.226s user: 0m0.000s sys: 0m0.048s
[1] qcow create   real: 0m1.990s user: 0m0.012s sys: 0m0.028s
[2] cp new        real: 0m0.037s user: 0m0.000s sys: 0m0.032s
[2] qcow create   real: 0m0.111s user: 0m0.008s sys: 0m0.016s
e2label           real: 0m0.999s user: 0m0.000s sys: 0m0.036s
tune2fs           real: 0m0.206s user: 0m0.004s sys: 0m0.004s
6.2M ephemeral0_ext3_10G.img
6.2M ephemeral0_ext3_10G.qcow2
6.2M new.img
136K new.qcow2
=== size=20G LABEL=ephemeral0 FSTYPE=ext3 ===
truncate          real: 0m0.023s user: 0m0.000s sys: 0m0.004s
mkfs.ext3         real: 0m15.542s user: 0m0.020s sys: 0m0.896s
cp working o      real: 0m0.641s user: 0m0.144s sys: 0m0.492s
cp working q      real: 0m0.248s user: 0m0.060s sys: 0m0.184s
rm working        real: 0m0.131s user: 0m0.000s sys: 0m0.128s
sync              real: 0m2.908s user: 0m0.004s sys: 0m0.000s
flush cache       real: 0m0.706s user: 0m0.000s sys: 0m0.044s
[1] cp new        real: 0m1.901s user: 0m0.004s sys: 0m0.072s
[1] qcow create   real: 0m2.190s user: 0m0.012s sys: 0m0.028s
[2] cp new        real: 0m0.056s user: 0m0.008s sys: 0m0.048s
[2] qcow create   real: 0m0.164s user: 0m0.008s sys: 0m0.016s
e2label           real: 0m1.582s user: 0m0.004s sys: 0m0.056s
tune2fs           real: 0m0.249s user: 0m0.004s sys: 0m0.004s
 11M ephemeral0_ext3_20G.img
 11M ephemeral0_ext3_20G.qcow2
 11M new.img
136K new.qcow2
=== size=100G LABEL=ephemeral0 FSTYPE=ext3 ===
truncate          real: 0m0.022s user: 0m0.000s sys: 0m0.004s
mkfs.ext3         real: 1m5.541s user: 0m0.156s sys: 0m4.388s
cp working o      real: 0m1.024s user: 0m0.336s sys: 0m0.684s
cp working q      real: 0m0.940s user: 0m0.216s sys: 0m0.720s
rm working        real: 0m0.563s user: 0m0.000s sys: 0m0.556s
sync              real: 0m13.101s user: 0m0.000s sys: 0m0.004s
flush cache       real: 0m0.643s user: 0m0.004s sys: 0m0.068s
[1] cp new        real: 0m6.992s user: 0m0.000s sys: 0m0.228s
[1] qcow create   real: 0m1.951s user: 0m0.008s sys: 0m0.032s
[2] cp new        real: 0m0.107s user: 0m0.008s sys: 0m0.096s
[2] qcow create   real: 0m0.118s user: 0m0.008s sys: 0m0.000s
e2label           real: 0m6.140s user: 0m0.004s sys: 0m0.264s
tune2fs           real: 0m0.298s user: 0m0.000s sys: 0m0.008s
 31M ephemeral0_ext3_100G.img
 31M ephemeral0_ext3_100G.qcow2
 31M new.img
136K new.qcow2

run-test

SIZE=${1:-20G}
LABEL="ephemeral0"
FSTYPE="ext3"
export TIMEFORMAT='real: %3lR user: %3lU sys: %3lS'

IMG_ORIG="${LABEL}_${FSTYPE}_${SIZE}.img"
IMG_NEW="new.img"
QIMG_ORIG="${IMG_ORIG%.img}.qcow2"
QIMG_NEW="${IMG_NEW%.img}.qcow2"
IMG_WORKING="$IMG.WORKING"
rm -f "$IMG_ORIG" "$IMG_NEW" "$QIMG_ORIG" "$QIMG_NEW" "$IMG_WORKING"

timeit() {
   local out=""
   printf "%-18s" "$1"
   local sudo=""
   [ "${SUDO:-0}" = "0" ] || sudo="sudo"
   time $sudo bash -fc "$2 >/dev/null 2>/dev/null" </dev/null
}

echo "=== size=$SIZE LABEL=$LABEL FSTYPE=$FSTYPE ==="

timeit "truncate"     "truncate --size $SIZE $IMG_WORKING"
timeit "mkfs.$FSTYPE" "mkfs.$FSTYPE -F -L $LABEL $IMG_WORKING"
timeit "cp working o" "cp --sparse=always $IMG_WORKING $IMG_ORIG"
timeit "cp working q" "cp --sparse=always $IMG_WORKING $QIMG_ORIG"
timeit "rm working"   "rm -f $IMG_WORKING"
timeit "sync"         "sync"
SUDO=1 timeit "flush cache"  "echo 3 | tee /proc/sys/vm/drop_caches"

for pass in 1 2; do
  rm -f $QIMG_NEW $IMG_NEW
  timeit "[$pass] cp new"       "cp --sparse=always $IMG_ORIG $IMG_NEW"
  timeit "[$pass] qcow create"  "qemu-img create -f qcow2 -b $QIMG_ORIG $QIMG_NEW"
done

timeit "e2label"      "e2label $IMG_NEW new_label"
timeit "tune2fs"      "tune2fs -U \$(uuidgen) $IMG_NEW"

ls -1hs $IMG_ORIG $IMG_NEW $QIMG_ORIG $QIMG_NEW