diff --git a/cluster/gce/util.sh b/cluster/gce/util.sh
index e6765594a6..8020629b05 100755
--- a/cluster/gce/util.sh
+++ b/cluster/gce/util.sh
@@ -132,6 +132,41 @@ function detect-project () {
   fi
 }
 
+function sha1sum-file() {
+  if which shasum >/dev/null 2>&1; then
+    shasum -a1 "$1" | awk '{ print $1 }'
+  else
+    sha1sum "$1" | awk '{ print $1 }'
+  fi
+}
+
+function already-staged() {
+  local -r file=$1
+  local -r newsum=$2
+
+  [[ -e "${file}.sha1" ]] || return 1
+
+  local oldsum
+  oldsum=$(cat "${file}.sha1")
+
+  [[ "${oldsum}" == "${newsum}" ]]
+}
+
+# Copy a release tar, if we don't already think it's staged in GCS
+function copy-if-not-staged() {
+  local -r staging_path=$1
+  local -r gs_url=$2
+  local -r tar=$3
+  local -r hash=$4
+
+  if already-staged "${tar}" "${hash}"; then
+    echo "+++ $(basename ${tar}) already staged ('rm ${tar}.sha1' to force)"
+  else
+    echo "${server_hash}" > "${tar}.sha1"
+    gsutil -m -q -h "Cache-Control:private, max-age=0" cp "${tar}" "${tar}.sha1" "${staging_path}"
+    gsutil -m acl ch -g all:R "${gs_url}" "${gs_url}.sha1" >/dev/null 2>&1
+  fi
+}
 
 # Take the local tar files and upload them to Google Storage.  They will then be
 # downloaded by the master as part of the start up script for the master.
@@ -153,6 +188,7 @@ function upload-server-tars() {
   else
     project_hash=$(echo -n "$PROJECT" | md5sum | awk '{ print $1 }')
   fi
+
   # This requires 1 million projects before the probability of collision is 50%
   # that's probably good enough for now :P
   project_hash=${project_hash:0:10}
@@ -167,13 +203,16 @@ function upload-server-tars() {
 
   local -r staging_path="${staging_bucket}/devel"
 
+  local server_hash
+  local salt_hash
+  server_hash=$(sha1sum-file "${SERVER_BINARY_TAR}")
+  salt_hash=$(sha1sum-file "${SALT_TAR}")
+
   echo "+++ Staging server tars to Google Storage: ${staging_path}"
   local server_binary_gs_url="${staging_path}/${SERVER_BINARY_TAR##*/}"
-  gsutil -q -h "Cache-Control:private, max-age=0" cp "${SERVER_BINARY_TAR}" "${server_binary_gs_url}"
-  gsutil acl ch -g all:R "${server_binary_gs_url}" >/dev/null 2>&1
   local salt_gs_url="${staging_path}/${SALT_TAR##*/}"
-  gsutil -q -h "Cache-Control:private, max-age=0" cp "${SALT_TAR}" "${salt_gs_url}"
-  gsutil acl ch -g all:R "${salt_gs_url}" >/dev/null 2>&1
+  copy-if-not-staged "${staging_path}" "${server_binary_gs_url}" "${SERVER_BINARY_TAR}" "${server_hash}"
+  copy-if-not-staged "${staging_path}" "${salt_gs_url}" "${SALT_TAR}" "${salt_hash}"
 
   # Convert from gs:// URL to an https:// URL
   SERVER_BINARY_TAR_URL="${server_binary_gs_url/gs:\/\//https://storage.googleapis.com/}"