diff --git a/lib/configuration.sh b/lib/configuration.sh
index a85184ab5..38958d703 100644
--- a/lib/configuration.sh
+++ b/lib/configuration.sh
@@ -29,6 +29,22 @@ ROOT_MAPPER="armbian-root"
 [[ -z $ROOTFS_TYPE ]] && ROOTFS_TYPE=ext4 # default rootfs type is ext4
 [[ "ext4 f2fs btrfs nfs fel" != *$ROOTFS_TYPE* ]] && exit_with_error "Unknown rootfs type" "$ROOTFS_TYPE"
 
+# check btrfs compression variable
+if [[ -n $BTRFS_COMPRESSION ]];then
+	btrfs_compression_ok=0
+	btrfs_cmp_chks="$(echo $BTRFS_COMPRESSION | sed -e 's/:[0-9]\+//')"
+	for c in lzo zlib zstd;do
+		[[ $c == $btrfs_cmp_chks ]] && btrfs_compression_ok=1 # ${BTRFS_COMPRESSION/:[0-9]+/} not works like zstd:12
+	done
+	if [[ $btrfs_compression_ok -eq 0 ]] ;then
+		display_alert "wrong btrfs compression method" "$BTRFS_COMPRESSION" 'err'
+		display_alert "set BTRFS_COMPRESSION to default" "lzo" "wrn"
+		BTRFS_COMPRESSION=lzo
+	fi
+	unset btrfs_compression_ok
+	unset btrfs_cmp_chks
+fi
+
 # Fixed image size is in 1M dd blocks (MiB)
 # to get size of block device /dev/sdX execute as root:
 # echo $(( $(blockdev --getsize64 /dev/sdX) / 1024 / 1024 ))
@@ -43,11 +59,12 @@ fi
 [[ $ROOTFS_TYPE == nfs ]] && FIXED_IMAGE_SIZE=64
 
 # used by multiple sources - reduce code duplication
-if [[ $USE_MAINLINE_GOOGLE_MIRROR == yes ]]; then
-	MAINLINE_KERNEL_SOURCE='https://kernel.googlesource.com/pub/scm/linux/kernel/git/stable/linux-stable'
-else
-	MAINLINE_KERNEL_SOURCE='git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git'
-fi
+[[ $USE_MAINLINE_GOOGLE_MIRROR == yes ]] && MAINLINE_MIRROR=google
+case $MAINLINE_MIRROR in
+	google) MAINLINE_KERNEL_SOURCE='https://kernel.googlesource.com/pub/scm/linux/kernel/git/stable/linux-stable' ;;
+	tuna) MAINLINE_KERNEL_SOURCE='https://mirrors.tuna.tsinghua.edu.cn/git/linux-stable.git' ;;
+	*) MAINLINE_KERNEL_SOURCE='git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git' ;;
+esac
 MAINLINE_KERNEL_DIR='linux-mainline'
 
 if [[ $USE_GITHUB_UBOOT_MIRROR == yes ]]; then
@@ -226,6 +243,11 @@ esac
 DEBIAN_MIRROR='httpredir.debian.org/debian'
 UBUNTU_MIRROR='ports.ubuntu.com/'
 
+if [[ $DOWNLOAD_MIRROR == china ]] ; then
+	DEBIAN_MIRROR='mirrors.tuna.tsinghua.edu.cn/debian'
+	UBUNTU_MIRROR='mirrors.tuna.tsinghua.edu.cn/ubuntu-ports/'
+fi
+
 # For user override
 if [[ -f $SRC/userpatches/lib.config ]]; then
 	display_alert "Using user configuration override" "userpatches/lib.config" "info"
diff --git a/lib/debootstrap-ng.sh b/lib/debootstrap-ng.sh
index acf8e783c..86a9a9996 100644
--- a/lib/debootstrap-ng.sh
+++ b/lib/debootstrap-ng.sh
@@ -296,7 +296,7 @@ prepare_partitions()
 	mkopts[fat]='-n BOOT'
 	mkopts[ext2]='-q'
 	# mkopts[f2fs] is empty
-	# mkopts[btrfs] is empty
+	mkopts[btrfs]='--data single --metadata single --label btrfs'
 	# mkopts[nfs] is empty
 
 	mkfs[ext4]=ext4
@@ -310,7 +310,7 @@ prepare_partitions()
 	# mountopts[ext2] is empty
 	# mountopts[fat] is empty
 	# mountopts[f2fs] is empty
-	mountopts[btrfs]=',commit=600,compress=lzo'
+	mountopts[btrfs]=",commit=600,compress=${BTRFS_COMPRESSION:-lzo}"
 	# mountopts[nfs] is empty
 
 	# stage: determine partition configuration
@@ -358,7 +358,7 @@ prepare_partitions()
 		case $ROOTFS_TYPE in
 			btrfs)
 				# Used for server images, currently no swap functionality, so disk space
-				# requirements are rather low since rootfs gets filled with compress-force=zlib
+				# requirements are rather low since rootfs gets filled with compress=$BTRFS_COMPRESSION
 				local sdsize=$(bc -l <<< "scale=0; (($imagesize * 0.8) / 4 + 1) * 4")
 				;;
 			*)
@@ -375,7 +375,7 @@ prepare_partitions()
 
 	# stage: create blank image
 	display_alert "Creating blank image for rootfs" "$sdsize MiB" "info"
-	dd if=/dev/zero bs=1M status=none count=$sdsize | pv -p -b -r -s $(( $sdsize * 1024 * 1024 )) | dd status=none of=${SDCARD}.raw
+	truncate --size=${sdsize}M ${SDCARD}.raw
 
 	# stage: calculate boot partition size
 	local bootstart=$(($OFFSET * 2048))
@@ -433,8 +433,25 @@ prepare_partitions()
 		display_alert "Creating rootfs" "$ROOTFS_TYPE on $rootdevice"
 		mkfs.${mkfs[$ROOTFS_TYPE]} ${mkopts[$ROOTFS_TYPE]} $rootdevice
 		[[ $ROOTFS_TYPE == ext4 ]] && tune2fs -o journal_data_writeback $rootdevice > /dev/null
-		[[ $ROOTFS_TYPE == btrfs ]] && local fscreateopt="-o compress-force=zlib"
+
+		local btrfs_space_cache_version=v1
+		local kernel_support_space_cache_v2=4.5
+		dpkg --compare-versions $VER 'gt' $kernel_support_space_cache_v2 && btrfs_space_cache_version=v2
+                [[ $ROOTFS_TYPE == btrfs ]] && local fscreateopt="-o compress=${BTRFS_COMPRESSION:-lzo},space_cache=${btrfs_space_cache_version}"
+		display_alert 'fscreateopt' "$fscreateopt" 'info'
+		unset btrfs_space_cache_version
+		unset kernel_support_space_cache_v2
+
 		mount ${fscreateopt} $rootdevice $MOUNT/
+                if [[ $ROOTFS_TYPE == btrfs ]];then
+                        btrfs subvolume create $MOUNT/@$RELEASE
+                        btrfs subvolume create $MOUNT/@home
+                        btrfs subvolume create $MOUNT/@boot
+                        umount $MOUNT
+                        mount ${fscreateopt},subvol=@$RELEASE $rootdevice $MOUNT/
+                        mkdir "$MOUNT/home"
+                        mount ${fscreateopt},subvol=@home $rootdevice $MOUNT/home
+                fi
 		# create fstab (and crypttab) entry
 		if [[ $CRYPTROOT_ENABLE == yes ]]; then
 			# map the LUKS container partition via its UUID to be the 'cryptroot' device
@@ -443,7 +460,13 @@ prepare_partitions()
 		else
 			local rootfs="UUID=$(blkid -s UUID -o value $rootdevice)"
 		fi
-		echo "$rootfs / ${mkfs[$ROOTFS_TYPE]} defaults,noatime,nodiratime${mountopts[$ROOTFS_TYPE]} 0 1" >> $SDCARD/etc/fstab
+
+                if [[ $ROOTFS_TYPE == btrfs ]]; then
+                        echo "$rootfs /     ${mkfs[$ROOTFS_TYPE]} defaults,noatime,nodiratime${mountopts[$ROOTFS_TYPE]},subvol=@$RELEASE     0 1" >> $SDCARD/etc/fstab
+                        echo "$rootfs /home ${mkfs[$ROOTFS_TYPE]} defaults,noatime,nodiratime${mountopts[$ROOTFS_TYPE]},subvol=@home 0 1" >> $SDCARD/etc/fstab
+                else
+                        echo "$rootfs / ${mkfs[$ROOTFS_TYPE]} defaults,noatime,nodiratime${mountopts[$ROOTFS_TYPE]} 0 1" >> $SDCARD/etc/fstab
+                fi
 	fi
 	if [[ -n $bootpart ]]; then
 		display_alert "Creating /boot" "$bootfs"
@@ -454,7 +477,7 @@ prepare_partitions()
 		echo "UUID=$(blkid -s UUID -o value ${LOOP}p${bootpart}) /boot ${mkfs[$bootfs]} defaults${mountopts[$bootfs]} 0 2" >> $SDCARD/etc/fstab
 	fi
 	[[ $ROOTFS_TYPE == nfs ]] && echo "/dev/nfs / nfs defaults 0 0" >> $SDCARD/etc/fstab
-	echo "tmpfs /tmp tmpfs defaults,nosuid 0 0" >> $SDCARD/etc/fstab
+	echo "tmpfs /media tmpfs defaults,nosuid 0 0" >> $SDCARD/etc/fstab
 
 	# stage: adjust boot script or boot environment
 	if [[ -f $SDCARD/boot/armbianEnv.txt ]]; then
@@ -492,6 +515,9 @@ prepare_partitions()
         fi
 	fi
 
+    # kernel args for btrfs subvolume
+    [[ $ROOTFS_TYPE == btrfs ]] && echo "extraargs=rootflags=subvol=@$RELEASE" >> $SDCARD/boot/armbianEnv.txt
+
 	# recompile .cmd to .scr if boot.cmd exists
 	[[ -f $SDCARD/boot/boot.cmd ]] && \
 		mkimage -C none -A arm -T script -d $SDCARD/boot/boot.cmd $SDCARD/boot/boot.scr > /dev/null 2>&1
@@ -536,7 +562,7 @@ create_image()
 
 	if [[ $ROOTFS_TYPE != nfs ]]; then
 		display_alert "Copying files to root directory"
-		rsync -aHWXh --exclude="/boot/*" --exclude="/dev/*" --exclude="/proc/*" --exclude="/run/*" --exclude="/tmp/*" \
+		rsync -aHWXh --inplace --exclude="/boot/*" --exclude="/dev/*" --exclude="/proc/*" --exclude="/run/*" --exclude="/tmp/*" \
 			--exclude="/sys/*" --info=progress2,stats1 $SDCARD/ $MOUNT/
 	else
 		display_alert "Creating rootfs archive" "rootfs.tgz" "info"
@@ -548,10 +574,10 @@ create_image()
 	display_alert "Copying files to /boot directory"
 	if [[ $(findmnt --target $MOUNT/boot -o FSTYPE -n) == vfat ]]; then
 		# fat32
-		rsync -rLtWh --info=progress2,stats1 $SDCARD/boot $MOUNT
+		rsync -rLtWh --inplace --info=progress2,stats1 $SDCARD/boot $MOUNT
 	else
 		# ext4
-		rsync -aHWXh --info=progress2,stats1 $SDCARD/boot $MOUNT
+		rsync -aHWXh --inplace --info=progress2,stats1 $SDCARD/boot $MOUNT
 	fi
 
 	# DEBUG: print free space
diff --git a/lib/general.sh b/lib/general.sh
index a3cd0f184..82fad1195 100644
--- a/lib/general.sh
+++ b/lib/general.sh
@@ -545,6 +545,8 @@ prepare_host()
 	curl patchutils python liblz4-tool libpython2.7-dev linux-base swig libpython-dev aptly acl \
 	locales ncurses-base pixz dialog systemd-container udev lib32stdc++6 libc6-i386 lib32ncurses5 lib32tinfo5 \
 	bison libbison-dev flex libfl-dev cryptsetup gpgv1 gnupg1 cpio"
+    
+	which aria2c >/dev/null || hostdeps="$hostdeps aria2"
 
 	local codename=$(lsb_release -sc)
 	display_alert "Build host OS release" "${codename:-(unknown)}" "info"
@@ -624,7 +626,7 @@ prepare_host()
 	# sync clock
 	if [[ $SYNC_CLOCK != no ]]; then
 		display_alert "Syncing clock" "host" "info"
-		ntpdate -s ${NTP_SERVER:- time.ijs.si}
+		ntpdate -s ${NTP_SERVER:- pool.ntp.org}
 	fi
 
 	if [[ $(dpkg-query -W -f='${db:Status-Abbrev}\n' 'zlib1g:i386' 2>/dev/null) != *ii* ]]; then
@@ -658,6 +660,9 @@ prepare_host()
 	# Use backup server by default to balance the load
 
 	ARMBIANSERVER=dl.armbian.com
+	if [[ $DOWNLOAD_MIRROR == 'china' ]]; then
+		ARMBIANSERVER='mirrors.tuna.tsinghua.edu.cn/armbian-releases'
+	fi
 
 	local toolchains=(
 		"https://${ARMBIANSERVER}/_toolchains/gcc-linaro-aarch64-none-elf-4.8-2013.11_linux.tar.xz"
@@ -671,7 +676,6 @@ prepare_host()
 		"https://${ARMBIANSERVER}/_toolchains/gcc-linaro-5.5.0-2017.10-x86_64_arm-linux-gnueabihf.tar.xz"
 		"https://${ARMBIANSERVER}/_toolchains/gcc-linaro-6.4.1-2017.11-x86_64_arm-linux-gnueabihf.tar.xz"
 		"https://${ARMBIANSERVER}/_toolchains/gcc-linaro-6.4.1-2017.11-x86_64_aarch64-linux-gnu.tar.xz"
-		"https://${ARMBIANSERVER}/_toolchains/gcc-linaro-7.4.1-2019.02-x86_64_aarch64-linux-gnu.tar.xz"
 		"https://${ARMBIANSERVER}/_toolchains/gcc-linaro-7.4.1-2019.02-x86_64_arm-linux-gnueabihf.tar.xz"
 		"https://${ARMBIANSERVER}/_toolchains/gcc-linaro-7.4.1-2019.02-x86_64_arm-eabi.tar.xz"
 		"https://${ARMBIANSERVER}/_toolchains/gcc-linaro-7.4.1-2019.02-x86_64_arm-linux-gnueabi.tar.xz"
@@ -718,6 +722,16 @@ prepare_host()
 	fi
 }
 
+# downloader() <url> <outputfilename>
+downloader()
+{
+	[ $# -ne 2 ] && exit_with_error "downloader args count" "$#"
+	args='--file-allocation=falloc --auto-file-renaming=false --continue=true --allow-overwrite=false'
+	display_alert "downloader args 1" "$1" "info"
+	display_alert "downloader args 2" "$2" "info"
+	aria2c $args "$1" -o "$2"
+}
+
 # download_toolchain <url>
 #
 download_toolchain()
@@ -733,8 +747,8 @@ download_toolchain()
 	cd $SRC/cache/toolchains/
 
 	display_alert "Downloading" "$dirname"
-	curl -Lf --progress-bar $url -o $filename
-	curl -Lf --progress-bar ${url}.asc -o ${filename}.asc
+	downloader $url $filename
+	downloader ${url}.asc ${filename}.asc
 
 	local verified=false
 
@@ -783,7 +797,7 @@ download_etcher_cli()
         cd $SRC/cache/utility/
 
         display_alert "Downloading" "$dirname"
-        curl -Lf --progress-bar $url -o $filename
+        downloader $url $filename
 
         local verified=false
 	local b=$(sha256sum $filename)
diff --git a/packages/extras/firmware.sh b/packages/extras/firmware.sh
index 43de2c065..13c9ea4da 100644
--- a/packages/extras/firmware.sh
+++ b/packages/extras/firmware.sh
@@ -14,14 +14,17 @@ build_firmware()
 	local plugin_repo="https://git.kernel.org/pub/scm/linux/kernel/git/firmware/linux-firmware.git"
 	local plugin_dir="armbian-firmware${FULL}"
 	[[ -d $SRC/cache/sources/$plugin_dir ]] && rm -rf $SRC/cache/sources/$plugin_dir
+	mkdir -p $SRC/cache/sources/$plugin_dir/lib/firmware
 
 	fetch_from_repo "https://github.com/armbian/firmware" "armbian-firmware-git" "branch:master"
 	if [[ -n $FULL ]]; then
-		fetch_from_repo "$plugin_repo" "$plugin_dir/lib/firmware" "branch:master"
+		fetch_from_repo "$plugin_repo" "linux-firmware-git" "branch:master"
+		# cp : create hardlinks
+		cp -alf $SRC/cache/sources/linux-firmware-git/* $SRC/cache/sources/$plugin_dir/lib/firmware/
 	fi
-	mkdir -p $SRC/cache/sources/$plugin_dir/lib/firmware
 	# overlay our firmware
-	cp -R $SRC/cache/sources/armbian-firmware-git/* $SRC/cache/sources/$plugin_dir/lib/firmware
+	# cp : create hardlinks
+	cp -alf $SRC/cache/sources/armbian-firmware-git/* $SRC/cache/sources/$plugin_dir/lib/firmware/
 
 	# cleanup what's not needed for sure
 	rm -rf $SRC/cache/sources/$plugin_dir/lib/firmware/{amdgpu,amd-ucode,radeon,nvidia,matrox,.git}
@@ -43,9 +46,9 @@ build_firmware()
 
 	cd $SRC/cache/sources
 	# pack
-	mv armbian-firmware${FULL} armbian-firmware${FULL}_${REVISION}_all
+	ln -s armbian-firmware${FULL} armbian-firmware${FULL}_${REVISION}_all
 	fakeroot dpkg -b armbian-firmware${FULL}_${REVISION}_all >> $DEST/debug/install.log 2>&1
-	mv armbian-firmware${FULL}_${REVISION}_all armbian-firmware${FULL}
+	rm armbian-firmware${FULL}_${REVISION}_all
 	mv armbian-firmware${FULL}_${REVISION}_all.deb $DEST/debs/ || display_alert "Failed moving firmware package" "" "wrn"
 }