aws-ebs-incremental-snapshot-diff.sh

#!/usr/bin/env bash

FIRST_SNAPSHOT=$1
SECOND_SNAPSHOT=$2

if [ -z "$FIRST_SNAPSHOT" ] || [ -z "$SECOND_SNAPSHOT" ]; then
  echo "Usage: $0 <first-snapshot-id> <second-snapshot-id>"
  exit 1
fi

echo "Comparing snapshots:"
echo "FROM: $FIRST_SNAPSHOT"
echo "TO:   $SECOND_SNAPSHOT"
echo

TOKEN=""
BLOCKS=0

while : ; do
  if [ -z "$TOKEN" ]; then
    RESP=$(aws ebs list-changed-blocks \
      --first-snapshot-id $FIRST_SNAPSHOT \
      --second-snapshot-id $SECOND_SNAPSHOT)
  else
    RESP=$(aws ebs list-changed-blocks \
      --first-snapshot-id $FIRST_SNAPSHOT \
      --second-snapshot-id $SECOND_SNAPSHOT \
      --next-token $TOKEN)
  fi

  COUNT=$(echo "$RESP" | jq '.ChangedBlocks | length')
  BLOCKS=$((BLOCKS + COUNT))

  TOKEN=$(echo "$RESP" | jq -r '.NextToken')

  if [ "$TOKEN" == "null" ]; then
    break
  fi
done

# Each block = 512 KiB
SIZE_KB=$((BLOCKS * 512))
SIZE_MB=$(echo "$SIZE_KB / 1024" | bc)
SIZE_GB=$(echo "scale=2; $SIZE_MB / 1024" | bc)

echo "Changed blocks: $BLOCKS"
echo "Incremental size:"
echo "  ${SIZE_KB} KB"
echo "  ${SIZE_MB} MB"
echo "  ${SIZE_GB} GB"