diff --git a/bwdatar b/bwdatar
index 1f90dba..ccc9db7 100755
--- a/bwdatar
+++ b/bwdatar
@@ -10,18 +10,25 @@ source $HOME/.bwda
 
 # Usage function
 usage(){
-  echo "Usage: $(basename $0) [opt] [dir]"
+  echo "Usage: $(basename $0) [opt] {push,pull} [dir]"
+  echo " {push,pull}              script mode: push directory to bwda, or pull it from there."
   echo " dir                      path to local directory on LSDF"
   echo " --include-size-mismatch  include files which mismatch in size to sync list"
-  echo " -n | --dry-run           print commands to stdout instead of executing them"
-  echo " -d | --tempdir dir       Path to the temporary directory where tar-file is created (default: \$PWD)"
+  echo " -c | --channel N         use N channels per file (pull only)"
+  echo " -d | --workdir dir       Path to the temporary directory where tar-file is created (default: \$PWD)"
   echo " -h | --help              display this message"
+  echo " -n | --dry-run           print commands to stdout instead of executing them"
+  echo " -P | --parallel N        transfer N files in parallel (pull only)"
+  echo " -s | --split bytes       chunk size of tar-archive in bytes. Default 500G. Expands K,M,G,KB,MB,GB. K=1024, KB=1000,..."
 }
 
 # Get command line argument
 flag_sizemismatch=false
 flag_dryrun=false
-tempdir=$PWD
+nparallel=1
+nchannel=1
+work_dir=$PWD
+bytes_split=500G
 
 POSITIONAL=()
 while [[ $# -gt 0 ]]
@@ -32,12 +39,27 @@ case $key in
     flag_sizemismatch=true
     shift
     ;;
+    -c|--channel)
+    nchannel=$2
+    shift
+    shift
+    ;;
+    -d|--work_dir)
+    work_dir="$2"
+    shift
+    shift
+    ;;
     -n|--dry-run)
     flag_dryrun=true
     shift
     ;;
-    -d|--tempdir)
-    tempdir="$2"
+    -P|--parallel)
+    nparallel=$2
+    shift
+    shift
+    ;;
+    -s|--split)
+    bytes_split=$2
     shift
     shift
     ;;
@@ -54,86 +76,232 @@ esac
 done
 set -- "${POSITIONAL[@]}" # restore positional parameters
 
-if [ $# -ne 1 ]; then
+if [ $# -ne 2 ]; then
   usage
   exit -1
 fi
 
-ldir_target="$(realpath $1)"
-if [ ! -d ${ldir_target} ]; then
-  >&2 echo "Not a directory: $1"
+# Set mode
+scriptmode=$1
+if [[ ! ${scriptmode} == 'push' ]] && [[ ! ${scriptmode} == 'pull' ]]; then
+    >&2 echo "Invalid mode: '$scriptmode'. (Valid: 'push','pull')"
+    exit -5
+fi
+
+# Set input directory and expand to absolute path
+input_dir="$(realpath $2)"
+if [[ $scriptmode == 'push' ]] && [[ ! -d ${input_dir} ]]; then
+  >&2 echo "Input is not a directory: $input_dir"
   exit -3
 fi
 
-# Get current path relative to base
-if [[ $ldir_target == "${ldir_base}"* ]]; then
-  dir_target=${ldir_target#"$ldir_base"}
-else
+# Set working directory where tar file will be stored temporarily
+work_dir=$(realpath ${work_dir})
+if [ ! -d ${work_dir} ]; then
+  >&2 echo "Workdir is not a directory: $work_dir"
+  exit -4
+fi
+
+# Validate nchannel and nparallel
+nchannel=$(printf %d $nchannel) 
+[[ $? -ne 0 ]] && >&2 echo "nchannel is not numeric." && exit 20
+nparallel=$(printf %d $nparallel) 
+[[ $? -ne 0 ]] && >&2 echo "nparallel is not numeric." && exit 20
+
+# Expand bytes_split
+bytes_split=${bytes_split/KB/*1000}
+bytes_split=${bytes_split/MB/*1000000}
+bytes_split=${bytes_split/GB/*1000000000}
+bytes_split=${bytes_split/K/*1024}
+bytes_split=${bytes_split/M/*1024**2}
+bytes_split=${bytes_split/G/*1024**3}
+if ! [[ $bytes_split =~ ^[0-9\*]+$ ]]; then
+    >&2 echo "bytes_split is not numeric."
+    exit 20
+fi
+bytes_split=$(( $bytes_split ))
+[[ $? -ne 0 ]] && >&2 echo "bytes_split is invalid." && exit 20
+
+# Set target directory relative to LSDF base directory
+if [[ ! $input_dir == "${ldir_base}"* ]]; then
   echo "Target directory is not located on LSDF!"
   echo "Is the base directory setting correct?"
   echo "ldir_base: $ldir_base"
   exit -2
 fi
+input_dir_rel=${input_dir#"$ldir_base"}     # path of input_dir relative to LSDF base directory
+target_dir_rel="$(dirname $input_dir_rel)"  # path of parent directory in which tar of input_dir will be located
+# echo $input_dir
+# echo $target_dir_rel
 
-# Construct name of tar file
-tar_exec_dir="$(dirname $ldir_target)"
-tar_target_dir="$(basename $ldir_target)"
-tar_filename="${tar_target_dir}.tar"
+# Construct base name of tar file: a number might be added if the file is split
+tar_exec_dir="$(dirname $input_dir)"        # directory from which tar is executed
+tar_target_dir="$(basename $input_dir)"     # input directory for tar command
+tar_filename="${tar_target_dir}.tar"        # file name of tar archive (trailing .XXXX may be added if archive needs to be split)
+
+# tar -cf - Ga_010 | split --numeric-suffixes --suffix-length=4 --bytes=100MB - chunk.split.
 
 # Construct paths of tar file
-rdir_target="$(dirname ${rdir_base}/${dir_target})"
-rfile_target="${rdir_target}/${tar_filename}"
-
-tempdir=$(realpath ${tempdir})
-ltmpfile="${tempdir}/${tar_filename}"
+rdir_target="${rdir_base}/${target_dir_rel}"
+# rfile_target="${rdir_target}/${tar_filenam`e}"
+lfile_target="${work_dir}/${tar_filename}"
 
 # Receive list of files on SFTP server, omit directories
 rfilelist=$(lftp sftp://${bwda_acc}@${bwda_url} -e "ls -l ${rdir_target}; bye" | grep -v '^d')
 rfilename=($(echo "$rfilelist" | awk '{print $9}'))
 rfilesize=($(echo "$rfilelist" | awk '{print $5}'))
 
-# Check if remote tar file already exists
-ipos=-1
+# Extract the relevant tar files. It should be a single file if its size is smaller than $bytes_split.
+# Otherwise the archive is split in several chunks
+nchunk=0
+chunkname=()
+chunksize=()
 for ir in ${!rfilename[@]}; do
-  if [[ ${rfilename[${ir}]} == ${tar_filename} ]]; then
-      ipos=$ir
-      break
+  if [[ ${rfilename[${ir}]} == "${tar_filename}"* ]]; then
+      chunkname[${nchunk}]=${rfilename[${ir}]}
+      chunksize[${nchunk}]=${rfilesize[${ir}]}
+      let nchunk=nchunk+1
   fi
 done
 
-# If file already exists, check if filesize matches
-if [[ $ipos -ge 0 ]]; then
-  filesize=$(cd ${tar_exec_dir}; \
-             tar cf /dev/null --totals ${tar_target_dir} 2>&1 | \
-             awk -F: '{print $2}' | awk '{print $1}')
-  if [[ ${rfilesize[${ipos}]} != ${filesize} ]]; then 
-    >&2 echo "Filesize mismatch: ${rfilename[${ipos}]}, HPSS=${rfilesize[${ipos}]}, estimate=${filesize}"
-    if [[ ! "$flag_sizemismatch" == true ]]; then
-        exit 10
+## MODE
+if [[ ${scriptmode} == 'pull' ]]; then
+    # Check if there is data to pull
+    if [[ $nchunk -lt 1 ]]; then
+        echo "Archive not available on bwda."
+        exit 51
+    fi
+    # Construct lftp command
+    cmd=""
+    cmd+="set cmd:parallel ${nparallel}; "
+    cmd+="cd ${rdir_target}; "
+    cmd+="lcd ${work_dir}; "
+    for chunk in "${chunkname[@]}"; do
+        cmd+="pget -n ${nchannel} $chunk; "
+    done
+    cmd+="bye" 
+    # Get files from bwda
+    lftp sftp://${bwda_acc}@${bwda_url} -e "$cmd"
+    ec=$?
+    if [[ $ec -ne 0 ]]; then
+        >&2 echo "lftp failed with status $ec."
+        exit 101
+    fi
+    # Extract archive
+    cat_args=""
+    for chunk in "${chunkname[@]}"; do
+        cat_args+="${work_dir}/${chunk} "
+    done
+    cat ${cat_args} | tar -C ${tar_exec_dir} -xkf -
+    ec=$?
+    if [[ $ec -ne 0 ]]; then
+        >&2 echo "tar failed with status $ec."
+        exit 100
+    fi
+    rm ${cat_args}
+elif [[ ${scriptmode} == 'push' ]]; then
+    # Estimate file size of archive
+    filesize_est=$(cd ${tar_exec_dir}; \
+                   tar cf /dev/null --totals ${tar_target_dir} 2>&1 | \
+                   awk -F: '{print $2}' | awk '{print $1}')
+    filesize_est=$(printf %d ${filesize_est})
+    # Get file size on bwda (if there are files already)
+    if [[ ${nchunk} -gt 0 ]]; then
+        filesize_bwda=0
+        for ((ii=0;ii<${nchunk};ii++)); do
+            let filesize_bwda=filesize_bwda+chunksize[ii]
+        done
+        filesize_bwda=$(printf %d ${filesize_bwda})
+    fi
+    # Check if file size matches 
+    if [[ ${nchunk} -gt 0 ]]; then
+        if [[ ${filesize_est} != ${filesize_bwda} ]]; then 
+            >&2 echo "Filesize mismatch: HPSS=${filesize_bwda}, estimate=${filesize_est}"
+            if [[ ! "$flag_sizemismatch" == true ]]; then
+                exit 10
+            fi
+        else
+            echo "File exists on BWDA and matches expected size. Not doing anything."
+            exit 0
+        fi
+    fi
+    # Estimate the number of chunks
+    nchunk_est=$(( ($filesize_est + $bytes_split - 1) / $bytes_split )) # ceil()
+    # 
+    if [ ${nchunk_est} -gt 1 ]; then
+        # nchunk>1: Asyncronously tar and upload available chunks
+        # trap "trap - SIGTERM && kill -- -$$" SIGINT SIGTERM EXIT
+        # trap 'kill $(jobs -pr)' SIGINT SIGTERM EXIT
+        # Define upload function to work asyncronously while archives are written
+        upload_to_bwda (){ # file, size
+            local chunk_file=$(realpath $1)
+            local chunk_size=$2
+            while ! ([[ -f ${chunk_file} ]] && [[ $(stat --printf=%s ${chunk_file}) -eq ${chunk_size} ]]); do
+                sleep 10
+            done
+            # local cur_size=$(stat --printf=%s ${chunk_file})
+            # while ; do
+            #     sleep 10
+            #     cur_size=$(stat --printf=%s ${chunk_file})
+            # done
+            lftp sftp://${bwda_acc}@${bwda_url} -e "cd ${rdir_target}; lcd ${work_dir}; put ${chunk_file}; bye"
+            return $?
+        }
+        # Create lists of subarchives and check if already exists
+        file_upload=()
+        for ((ii=0;ii<${nchunk_est};ii++)); do
+            file_upload[${ii}]=${lfile_target}.$(printf %04d $ii)
+            if [ -f ${file_upload[${ii}]} ]; then
+                >&2 echo "Error: temporary file ${file_upload[${ii}]} exists. Refusing to overwrite."
+                exit 90
+            fi
+        done
+        # Create tar archive
+        tar -C ${tar_exec_dir} -cf - ${tar_target_dir} | split --numeric-suffixes --suffix-length=4 --bytes=${bytes_split} - ${lfile_target}. &
+        pid_tar=$!
+        # Start upload tasks
+        pid_upload=()
+        echo $nchunk_est
+        for (( ii=0;ii<${nchunk_est}-1;ii++ )); do
+            upload_to_bwda ${file_upload[${ii}]} ${bytes_split} &
+            pid_upload[${ii}]=$!
+        done
+        upload_to_bwda ${file_upload[${ii}]} $(( $filesize_est % ${bytes_split} )) &
+        pid_upload[${ii}]=$!
+        # Wait for tar process
+        wait $pid_tar
+        ec=$?
+        if [[ $ec -ne 0 ]]; then
+            >&2 echo "tar failed with status $ec."
+            exit 100
+        fi
+        # Wait for upload processes
+        for ((ii=0;ii<${nchunk_est};ii++)); do
+            wait ${pid_upload[${ii}]}
+            ec=$?
+            if [[ $ec -ne 0 ]]; then
+                >&2 echo "lftp failed with status $ec."
+                exit 101
+            fi
+            rm ${file_upload[${ii}]}
+        done
+    else 
+        # nchunk=1: tar and upload are done sequentially
+        # Create tar archive
+        tar -C ${tar_exec_dir} -cf ${lfile_target} ${tar_target_dir}
+        ec=$?
+        if [[ $ec -ne 0 ]]; then
+            >&2 echo "tar failed with status $ec."
+            exit 100
+        fi
+        # Upload archive
+        lftp sftp://${bwda_acc}@${bwda_url} -e "cd ${rdir_target}; lcd ${work_dir}; put ${tar_filename}; bye"
+        ec=$?
+        if [[ $ec -ne 0 ]]; then
+            >&2 echo "lftp failed with status $ec."
+            exit 101
+        fi
+        # Remove temporary archive
+        rm ${lfile_target}
     fi
-  else
-    echo "Nothing to sync."
-    exit 0
-  fi
-fi
-
-# Write a lftp batch script for syncing
->&2 echo "Uploading ${rdir_target}/${tar_filename}"
-cmd="open sftp://${bwda_acc}@${bwda_url}\n"
-cmd+="set cmd:parallel 1\n"
-cmd+="cd ${rdir_target}\n"
-cmd+="lcd ${tempdir}\n"
-cmd+="put -c ${tar_filename}\n"
-cmd+="bye\n"
-
-# Execute
-if [[ "$flag_dryrun" == true ]]; then
-  printf "$cmd"
-else
-  (cd ${tar_exec_dir}; tar cf ${ltmpfile} ${tar_target_dir})
-  tmpfile=$(mktemp)
-  printf "$cmd" > $tmpfile
-  lftp -f $tmpfile
-  rm $tmpfile  
-  rm ${ltmpfile}
 fi