Add compression using zstd (#173)

fix #27

Co-authored-by: Trinity Pointard <trinity.pointard@gmail.com>
Reviewed-on: https://git.deuxfleurs.fr/Deuxfleurs/garage/pulls/173
Co-authored-by: trinity-1686a <trinity.pointard@gmail.com>
Co-committed-by: trinity-1686a <trinity.pointard@gmail.com>

8 files changed, 377 insertions, 53 deletions

diff --git a/Cargo.lock b/Cargo.lock
index 8f81c098..c07acac2 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -106,6 +106,9 @@ name = "cc"
 version = "1.0.71"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "79c2681d6594606957bbb8631c4b90a7fcaaa72cdb714743a437b156d6a7eedd"
+dependencies = [
+ "jobserver",
+]
 
 [[package]]
 name = "cfg-if"
@@ -458,6 +461,7 @@ dependencies = [
  "serde_bytes",
  "sled",
  "tokio",
+ "zstd",
 ]
 
 [[package]]
@@ -753,6 +757,15 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b71991ff56294aa922b450139ee08b3bfc70982c6b2c7562771375cf73542dd4"
 
 [[package]]
+name = "jobserver"
+version = "0.1.24"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "af25a77299a7f711a01975c35a6a424eb6862092cc2d6c72c4ed6cbc56dfc1fa"
+dependencies = [
+ "libc",
+]
+
+[[package]]
 name = "kuska-handshake"
 version = "0.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -1652,3 +1665,32 @@ name = "xxhash-rust"
 version = "0.8.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e575e15bedf6e57b5c2d763ffc6c3c760143466cbd09d762d539680ab5992ded"
+
+[[package]]
+name = "zstd"
+version = "0.9.0+zstd.1.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "07749a5dc2cb6b36661290245e350f15ec3bbb304e493db54a1d354480522ccd"
+dependencies = [
+ "zstd-safe",
+]
+
+[[package]]
+name = "zstd-safe"
+version = "4.1.1+zstd.1.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c91c90f2c593b003603e5e0493c837088df4469da25aafff8bce42ba48caf079"
+dependencies = [
+ "libc",
+ "zstd-sys",
+]
+
+[[package]]
+name = "zstd-sys"
+version = "1.6.1+zstd.1.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "615120c7a2431d16cf1cf979e7fc31ba7a5b5e5707b29c8a99e5dbf8a8392a33"
+dependencies = [
+ "cc",
+ "libc",
+]
diff --git a/Cargo.nix b/Cargo.nix
index 2e0804d5..5b38c55e 100644
--- a/Cargo.nix
+++ b/Cargo.nix
@@ -196,6 +196,13 @@ in
     version = "1.0.71";
     registry = "registry+https://github.com/rust-lang/crates.io-index";
     src = fetchCratesIo { inherit name version; sha256 = "79c2681d6594606957bbb8631c4b90a7fcaaa72cdb714743a437b156d6a7eedd"; };
+    features = builtins.concatLists [
+      [ "jobserver" ]
+      [ "parallel" ]
+    ];
+    dependencies = {
+      jobserver = rustPackages."registry+https://github.com/rust-lang/crates.io-index".jobserver."0.1.24" { inherit profileName; };
+    };
   });
   
   "registry+https://github.com/rust-lang/crates.io-index".cfg-if."1.0.0" = overridableMkRustCrate (profileName: rec {
@@ -695,6 +702,7 @@ in
       serde_bytes = rustPackages."registry+https://github.com/rust-lang/crates.io-index".serde_bytes."0.11.5" { inherit profileName; };
       sled = rustPackages."registry+https://github.com/rust-lang/crates.io-index".sled."0.34.7" { inherit profileName; };
       tokio = rustPackages."registry+https://github.com/rust-lang/crates.io-index".tokio."1.12.0" { inherit profileName; };
+      zstd = rustPackages."registry+https://github.com/rust-lang/crates.io-index".zstd."0.9.0+zstd.1.5.0" { inherit profileName; };
     };
   });
   
@@ -1055,6 +1063,16 @@ in
     ];
   });
   
+  "registry+https://github.com/rust-lang/crates.io-index".jobserver."0.1.24" = overridableMkRustCrate (profileName: rec {
+    name = "jobserver";
+    version = "0.1.24";
+    registry = "registry+https://github.com/rust-lang/crates.io-index";
+    src = fetchCratesIo { inherit name version; sha256 = "af25a77299a7f711a01975c35a6a424eb6862092cc2d6c72c4ed6cbc56dfc1fa"; };
+    dependencies = {
+      ${ if hostPlatform.isUnix then "libc" else null } = rustPackages."registry+https://github.com/rust-lang/crates.io-index".libc."0.2.103" { inherit profileName; };
+    };
+  });
+  
   "registry+https://github.com/rust-lang/crates.io-index".kuska-handshake."0.2.0" = overridableMkRustCrate (profileName: rec {
     name = "kuska-handshake";
     version = "0.2.0";
@@ -2351,4 +2369,44 @@ in
     ];
   });
   
+  "registry+https://github.com/rust-lang/crates.io-index".zstd."0.9.0+zstd.1.5.0" = overridableMkRustCrate (profileName: rec {
+    name = "zstd";
+    version = "0.9.0+zstd.1.5.0";
+    registry = "registry+https://github.com/rust-lang/crates.io-index";
+    src = fetchCratesIo { inherit name version; sha256 = "07749a5dc2cb6b36661290245e350f15ec3bbb304e493db54a1d354480522ccd"; };
+    dependencies = {
+      zstd_safe = rustPackages."registry+https://github.com/rust-lang/crates.io-index".zstd-safe."4.1.1+zstd.1.5.0" { inherit profileName; };
+    };
+  });
+  
+  "registry+https://github.com/rust-lang/crates.io-index".zstd-safe."4.1.1+zstd.1.5.0" = overridableMkRustCrate (profileName: rec {
+    name = "zstd-safe";
+    version = "4.1.1+zstd.1.5.0";
+    registry = "registry+https://github.com/rust-lang/crates.io-index";
+    src = fetchCratesIo { inherit name version; sha256 = "c91c90f2c593b003603e5e0493c837088df4469da25aafff8bce42ba48caf079"; };
+    features = builtins.concatLists [
+      [ "std" ]
+    ];
+    dependencies = {
+      libc = rustPackages."registry+https://github.com/rust-lang/crates.io-index".libc."0.2.103" { inherit profileName; };
+      zstd_sys = rustPackages."registry+https://github.com/rust-lang/crates.io-index".zstd-sys."1.6.1+zstd.1.5.0" { inherit profileName; };
+    };
+  });
+  
+  "registry+https://github.com/rust-lang/crates.io-index".zstd-sys."1.6.1+zstd.1.5.0" = overridableMkRustCrate (profileName: rec {
+    name = "zstd-sys";
+    version = "1.6.1+zstd.1.5.0";
+    registry = "registry+https://github.com/rust-lang/crates.io-index";
+    src = fetchCratesIo { inherit name version; sha256 = "615120c7a2431d16cf1cf979e7fc31ba7a5b5e5707b29c8a99e5dbf8a8392a33"; };
+    features = builtins.concatLists [
+      [ "std" ]
+    ];
+    dependencies = {
+      libc = rustPackages."registry+https://github.com/rust-lang/crates.io-index".libc."0.2.103" { inherit profileName; };
+    };
+    buildDependencies = {
+      cc = buildRustPackages."registry+https://github.com/rust-lang/crates.io-index".cc."1.0.71" { profileName = "__noProfile"; };
+    };
+  });
+  
 }
diff --git a/doc/book/src/cookbook/real_world.md b/doc/book/src/cookbook/real_world.md
index d1303d47..906fe31f 100644
--- a/doc/book/src/cookbook/real_world.md
+++ b/doc/book/src/cookbook/real_world.md
@@ -74,6 +74,8 @@ data_dir = "/var/lib/garage/data"
 
 replication_mode = "3"
 
+compression_level = 2
+
 rpc_bind_addr = "[::]:3901"
 rpc_public_addr = "<this node's public IP>:3901"
 rpc_secret = "<RPC secret>"
diff --git a/doc/book/src/reference_manual/configuration.md b/doc/book/src/reference_manual/configuration.md
index 0b1e7bc7..9f88b232 100644
--- a/doc/book/src/reference_manual/configuration.md
+++ b/doc/book/src/reference_manual/configuration.md
@@ -10,6 +10,8 @@ block_size = 1048576
 
 replication_mode = "3"
 
+compression_level = 1
+
 rpc_secret = "4425f5c26c5e11581d3223904324dcb5b5d5dfb14e5e7f35e38c595424f5f1e6"
 rpc_bind_addr = "[::]:3901"
 rpc_public_addr = "[fc00:1::1]:3901"
@@ -98,6 +100,30 @@ Never run a Garage cluster where that is not the case.**
 Changing the `replication_mode` of a cluster might work (make sure to shut down all nodes
 and changing it everywhere at the time), but is not officially supported.
 
+### `compression_level`
+
+Zstd compression level to use for storing blocks.
+
+Values between `1` (faster compression) and `19` (smaller file) are standard compression
+levels for zstd. From `20` to `22`, compression levels are referred as "ultra" and must be
+used with extra care as it will use lot of memory. A value of `0` will let zstd choose a
+default value (currently `3`). Finally, zstd has also compression designed to be faster
+than default compression levels, they range from `-1` (smaller file) to `-99` (faster 
+compression).
+
+If you do not specify a `compression_level` entry, garage will set it to `1` for you. With
+this parameters, zstd consumes low amount of cpu and should work faster than line speed in
+most situations, while saving some space and intra-cluster
+bandwidth.
+
+If you want to totally deactivate zstd in garage, you can pass the special value `'none'`. No
+zstd related code will be called, your chunks will be stored on disk without any processing.
+
+Compression is done synchronously, setting a value too high will add latency to write queries.
+
+This value can be different between nodes, compression is done by the node which receive the
+API call.
+
 #### `rpc_secret`
 
 Garage uses a secret key that is shared between all nodes of the cluster
diff --git a/script/test-smoke.sh b/script/test-smoke.sh
index 3146e637..1f900ece 100755
--- a/script/test-smoke.sh
+++ b/script/test-smoke.sh
@@ -30,6 +30,11 @@ dd if=/dev/urandom of=/tmp/garage.1.rnd bs=1k count=2 # No multipart, inline sto
 dd if=/dev/urandom of=/tmp/garage.2.rnd bs=1M count=5 # No multipart but file will be chunked
 dd if=/dev/urandom of=/tmp/garage.3.rnd bs=1M count=10 # by default, AWS starts using multipart at 8MB
 
+# data of lower entropy, to test compression
+dd if=/dev/urandom bs=1k count=2  | base64 -w0 > /tmp/garage.1.b64
+dd if=/dev/urandom bs=1M count=5  | base64 -w0 > /tmp/garage.2.b64
+dd if=/dev/urandom bs=1M count=10 | base64 -w0 > /tmp/garage.3.b64
+
 echo "🧪 S3 API testing..."
 
 # AWS
@@ -37,11 +42,11 @@ if [ -z "$SKIP_AWS" ]; then
   echo "🛠️ Testing with awscli"
   source ${SCRIPT_FOLDER}/dev-env-aws.sh
   aws s3 ls
-  for idx in $(seq 1 3); do
-    aws s3 cp "/tmp/garage.$idx.rnd" "s3://eprouvette/&+-é\"/garage.$idx.aws"
+  for idx in {1..3}.{rnd,b64}; do
+    aws s3 cp "/tmp/garage.$idx" "s3://eprouvette/&+-é\"/garage.$idx.aws"
     aws s3 ls s3://eprouvette
     aws s3 cp "s3://eprouvette/&+-é\"/garage.$idx.aws" "/tmp/garage.$idx.dl"
-    diff /tmp/garage.$idx.rnd /tmp/garage.$idx.dl
+    diff /tmp/garage.$idx /tmp/garage.$idx.dl
     rm /tmp/garage.$idx.dl
     aws s3 rm "s3://eprouvette/&+-é\"/garage.$idx.aws"
   done
@@ -52,11 +57,11 @@ if [ -z "$SKIP_S3CMD" ]; then
   echo "🛠️ Testing with s3cmd"
   source ${SCRIPT_FOLDER}/dev-env-s3cmd.sh
   s3cmd ls
-  for idx in $(seq 1 3); do
-    s3cmd put "/tmp/garage.$idx.rnd" "s3://eprouvette/&+-é\"/garage.$idx.s3cmd"
+  for idx in {1..3}.{rnd,b64}; do
+    s3cmd put "/tmp/garage.$idx" "s3://eprouvette/&+-é\"/garage.$idx.s3cmd"
     s3cmd ls s3://eprouvette
     s3cmd get "s3://eprouvette/&+-é\"/garage.$idx.s3cmd" "/tmp/garage.$idx.dl"
-    diff /tmp/garage.$idx.rnd /tmp/garage.$idx.dl
+    diff /tmp/garage.$idx /tmp/garage.$idx.dl
     rm /tmp/garage.$idx.dl
     s3cmd rm "s3://eprouvette/&+-é\"/garage.$idx.s3cmd"
   done
@@ -67,11 +72,11 @@ if [ -z "$SKIP_MC" ]; then
   echo "🛠️ Testing with mc (minio client)"
   source ${SCRIPT_FOLDER}/dev-env-mc.sh
   mc ls garage/
-  for idx in $(seq 1 3); do
-    mc cp "/tmp/garage.$idx.rnd" "garage/eprouvette/&+-é\"/garage.$idx.mc"
+  for idx in {1..3}.{rnd,b64}; do
+    mc cp "/tmp/garage.$idx" "garage/eprouvette/&+-é\"/garage.$idx.mc"
     mc ls garage/eprouvette
     mc cp "garage/eprouvette/&+-é\"/garage.$idx.mc" "/tmp/garage.$idx.dl"
-    diff /tmp/garage.$idx.rnd /tmp/garage.$idx.dl
+    diff /tmp/garage.$idx /tmp/garage.$idx.dl
     rm /tmp/garage.$idx.dl
     mc rm "garage/eprouvette/&+-é\"/garage.$idx.mc"
   done
@@ -82,13 +87,13 @@ if [ -z "$SKIP_RCLONE" ]; then
   echo "🛠️ Testing with rclone"
   source ${SCRIPT_FOLDER}/dev-env-rclone.sh
   rclone lsd garage:
-  for idx in $(seq 1 3); do
-    cp /tmp/garage.$idx.rnd /tmp/garage.$idx.dl
+  for idx in {1..3}.{rnd,b64}; do
+    cp /tmp/garage.$idx /tmp/garage.$idx.dl
     rclone copy "/tmp/garage.$idx.dl" "garage:eprouvette/&+-é\"/"
     rm /tmp/garage.$idx.dl
     rclone ls garage:eprouvette
     rclone copy "garage:eprouvette/&+-é\"/garage.$idx.dl" "/tmp/"
-    diff /tmp/garage.$idx.rnd /tmp/garage.$idx.dl
+    diff /tmp/garage.$idx /tmp/garage.$idx.dl
     rm /tmp/garage.$idx.dl
     rclone delete "garage:eprouvette/&+-é\"/garage.$idx.dl"
   done
@@ -100,17 +105,17 @@ if [ -z "$SKIP_DUCK" ]; then
   source ${SCRIPT_FOLDER}/dev-env-duck.sh
   duck --list garage:/
   duck --mkdir "garage:/eprouvette/duck"
-  for idx in $(seq 1 3); do
-    duck --verbose --upload "garage:/eprouvette/duck/" "/tmp/garage.$idx.rnd" 
+  for idx in {1..3}.{rnd,b64}; do
+    duck --verbose --upload "garage:/eprouvette/duck/" "/tmp/garage.$idx"
     duck --list garage:/eprouvette/duck/
-    duck --download "garage:/eprouvette/duck/garage.$idx.rnd" "/tmp/garage.$idx.dl"
-    diff /tmp/garage.$idx.rnd /tmp/garage.$idx.dl
+    duck --download "garage:/eprouvette/duck/garage.$idx" "/tmp/garage.$idx.dl"
+    diff /tmp/garage.$idx /tmp/garage.$idx.dl
     rm /tmp/garage.$idx.dl
     duck --delete "garage:/eprouvette/duck/garage.$idx.dk"
   done
 fi
 
-rm /tmp/garage.{1,2,3}.rnd
+rm /tmp/garage.{1..3}.{rnd,b64}
 
 if [ -z "$SKIP_AWS" ]; then
   echo "🧪 Website Testing"
diff --git a/src/model/Cargo.toml b/src/model/Cargo.toml
index 7979a79a..1d695192 100644
--- a/src/model/Cargo.toml
+++ b/src/model/Cargo.toml
@@ -23,6 +23,7 @@ arc-swap = "1.0"
 hex = "0.4"
 log = "0.4"
 rand = "0.8"
+zstd = { version = "0.9", default-features = false }
 
 sled = "0.34"
 
diff --git a/src/model/block.rs b/src/model/block.rs
index 8b1919bb..6df8e265 100644
--- a/src/model/block.rs
+++ b/src/model/block.rs
@@ -11,6 +11,7 @@ use serde::{Deserialize, Serialize};
 use tokio::fs;
 use tokio::io::{AsyncReadExt, AsyncWriteExt};
 use tokio::sync::{watch, Mutex, Notify};
+use zstd::stream::{decode_all as zstd_decode, Encoder};
 
 use garage_util::data::*;
 use garage_util::error::*;
@@ -55,22 +56,81 @@ pub enum BlockRpc {
 	GetBlock(Hash),
 	/// Message to send a block of data, either because requested, of for first delivery of new
 	/// block
-	PutBlock(PutBlockMessage),
+	PutBlock {
+		hash: Hash,
+		data: DataBlock,
+	},
 	/// Ask other node if they should have this block, but don't actually have it
 	NeedBlockQuery(Hash),
 	/// Response : whether the node do require that block
 	NeedBlockReply(bool),
 }
 
-/// Structure used to send a block
+/// A possibly compressed block of data
 #[derive(Debug, Serialize, Deserialize)]
-pub struct PutBlockMessage {
-	/// Hash of the block
-	pub hash: Hash,
+pub enum DataBlock {
+	/// Uncompressed data
+	Plain(#[serde(with = "serde_bytes")] Vec<u8>),
+	/// Data compressed with zstd
+	Compressed(#[serde(with = "serde_bytes")] Vec<u8>),
+}
+
+impl DataBlock {
+	/// Query whether this block is compressed
+	pub fn is_compressed(&self) -> bool {
+		matches!(self, DataBlock::Compressed(_))
+	}
+
+	/// Get the inner, possibly compressed buffer. You should probably use [`DataBlock::verify_get`]
+	/// instead
+	pub fn inner_buffer(&self) -> &[u8] {
+		use DataBlock::*;
+		let (Plain(ref res) | Compressed(ref res)) = self;
+		res
+	}
 
-	/// Content of the block
-	#[serde(with = "serde_bytes")]
-	pub data: Vec<u8>,
+	/// Get the buffer, possibly decompressing it, and verify it's integrity.
+	/// For Plain block, data is compared to hash, for Compressed block, zstd checksumming system
+	/// is used instead.
+	pub fn verify_get(self, hash: Hash) -> Result<Vec<u8>, Error> {
+		match self {
+			DataBlock::Plain(data) => {
+				if blake2sum(&data) == hash {
+					Ok(data)
+				} else {
+					Err(Error::CorruptData(hash))
+				}
+			}
+			DataBlock::Compressed(data) => {
+				zstd_decode(&data[..]).map_err(|_| Error::CorruptData(hash))
+			}
+		}
+	}
+
+	/// Verify data integrity. Allocate less than [`DataBlock::verify_get`] and don't consume self, but
+	/// does not return the buffer content.
+	pub fn verify(&self, hash: Hash) -> Result<(), Error> {
+		match self {
+			DataBlock::Plain(data) => {
+				if blake2sum(data) == hash {
+					Ok(())
+				} else {
+					Err(Error::CorruptData(hash))
+				}
+			}
+			DataBlock::Compressed(data) => zstd::stream::copy_decode(&data[..], std::io::sink())
+				.map_err(|_| Error::CorruptData(hash)),
+		}
+	}
+
+	pub fn from_buffer(data: Vec<u8>, level: Option<i32>) -> DataBlock {
+		if let Some(level) = level {
+			if let Ok(data) = zstd_encode(&data[..], level) {
+				return DataBlock::Compressed(data);
+			}
+		}
+		DataBlock::Plain(data)
+	}
 }
 
 impl Rpc for BlockRpc {
@@ -138,10 +198,8 @@ impl BlockManager {
 		block_manager
 	}
 
-	// ---- Public interface ----
-
-	/// Ask nodes that might have a block for it
-	pub async fn rpc_get_block(&self, hash: &Hash) -> Result<Vec<u8>, Error> {
+	/// Ask nodes that might have a (possibly compressed) block for it
+	async fn rpc_get_raw_block(&self, hash: &Hash) -> Result<DataBlock, Error> {
 		let who = self.replication.read_nodes(hash);
 		let resps = self
 			.system
@@ -158,8 +216,8 @@ impl BlockManager {
 			.await?;
 
 		for resp in resps {
-			if let BlockRpc::PutBlock(msg) = resp {
-				return Ok(msg.data);
+			if let BlockRpc::PutBlock { data, .. } = resp {
+				return Ok(data);
 			}
 		}
 		Err(Error::Message(format!(
@@ -168,15 +226,30 @@ impl BlockManager {
 		)))
 	}
 
+	// ---- Public interface ----
+
+	/// Ask nodes that might have a block for it
+	pub async fn rpc_get_block(&self, hash: &Hash) -> Result<Vec<u8>, Error> {
+		self.rpc_get_raw_block(hash).await?.verify_get(*hash)
+	}
+
 	/// Send block to nodes that should have it
 	pub async fn rpc_put_block(&self, hash: Hash, data: Vec<u8>) -> Result<(), Error> {
 		let who = self.replication.write_nodes(&hash);
+		let compression_level = self
+			.garage
+			.load()
+			.as_ref()
+			.unwrap()
+			.config
+			.compression_level;
+		let data = DataBlock::from_buffer(data, compression_level);
 		self.system
 			.rpc
 			.try_call_many(
 				&self.endpoint,
 				&who[..],
-				BlockRpc::PutBlock(PutBlockMessage { hash, data }),
+				BlockRpc::PutBlock { hash, data },
 				RequestStrategy::with_priority(PRIO_NORMAL)
 					.with_quorum(self.replication.write_quorum())
 					.with_timeout(BLOCK_RW_TIMEOUT),
@@ -306,7 +379,7 @@ impl BlockManager {
 	// ---- Reading and writing blocks locally ----
 
 	/// Write a block to disk
-	async fn write_block(&self, hash: &Hash, data: &[u8]) -> Result<BlockRpc, Error> {
+	async fn write_block(&self, hash: &Hash, data: &DataBlock) -> Result<BlockRpc, Error> {
 		self.mutation_lock
 			.lock()
 			.await
@@ -316,21 +389,31 @@ impl BlockManager {
 
 	/// Read block from disk, verifying it's integrity
 	async fn read_block(&self, hash: &Hash) -> Result<BlockRpc, Error> {
-		let path = self.block_path(hash);
-
-		let mut f = match fs::File::open(&path).await {
-			Ok(f) => f,
+		let mut path = self.block_path(hash);
+		let compressed = match self.is_block_compressed(hash).await {
+			Ok(c) => c,
 			Err(e) => {
 				// Not found but maybe we should have had it ??
 				self.put_to_resync(hash, 2 * BLOCK_RW_TIMEOUT)?;
 				return Err(Into::into(e));
 			}
 		};
+		if compressed {
+			path.set_extension("zst");
+		}
+		let mut f = fs::File::open(&path).await?;
+
 		let mut data = vec![];
 		f.read_to_end(&mut data).await?;
 		drop(f);
 
-		if blake2sum(&data[..]) != *hash {
+		let data = if compressed {
+			DataBlock::Compressed(data)
+		} else {
+			DataBlock::Plain(data)
+		};
+
+		if data.verify(*hash).is_err() {
 			self.mutation_lock
 				.lock()
 				.await
@@ -340,7 +423,7 @@ impl BlockManager {
 			return Err(Error::CorruptData(*hash));
 		}
 
-		Ok(BlockRpc::PutBlock(PutBlockMessage { hash: *hash, data }))
+		Ok(BlockRpc::PutBlock { hash: *hash, data })
 	}
 
 	/// Check if this node should have a block, but don't actually have it
@@ -362,13 +445,25 @@ impl BlockManager {
 		path
 	}
 
-	/// Utility: give the full path where a block should be found
+	/// Utility: give the full path where a block should be found, minus extension if block is
+	/// compressed
 	fn block_path(&self, hash: &Hash) -> PathBuf {
 		let mut path = self.block_dir(hash);
 		path.push(hex::encode(hash.as_ref()));
 		path
 	}
 
+	/// Utility: check if block is stored compressed. Error if block is not stored
+	async fn is_block_compressed(&self, hash: &Hash) -> Result<bool, Error> {
+		let mut path = self.block_path(hash);
+		path.set_extension("zst");
+		if fs::metadata(&path).await.is_ok() {
+			return Ok(true);
+		}
+		path.set_extension("");
+		fs::metadata(&path).await.map(|_| false).map_err(Into::into)
+	}
+
 	// ---- Resync loop ----
 
 	pub fn spawn_background_worker(self: Arc<Self>) {
@@ -550,8 +645,8 @@ impl BlockManager {
 				hash
 			);
 
-			let block_data = self.rpc_get_block(hash).await?;
-			self.write_block(hash, &block_data[..]).await?;
+			let block_data = self.rpc_get_raw_block(hash).await?;
+			self.write_block(hash, &block_data).await?;
 		}
 
 		Ok(())
@@ -602,6 +697,7 @@ impl BlockManager {
 				};
 				let ent_type = data_dir_ent.file_type().await?;
 
+				let name = name.strip_suffix(".zst").unwrap_or(&name);
 				if name.len() == 2 && hex::decode(&name).is_ok() && ent_type.is_dir() {
 					state = self
 						.for_each_file_rec(&data_dir_ent.path(), state, f, must_exit)
@@ -631,7 +727,7 @@ impl EndpointHandler<BlockRpc> for BlockManager {
 		_from: NodeID,
 	) -> Result<BlockRpc, Error> {
 		match message {
-			BlockRpc::PutBlock(m) => self.write_block(&m.hash, &m.data).await,
+			BlockRpc::PutBlock { hash, data } => self.write_block(hash, data).await,
 			BlockRpc::GetBlock(h) => self.read_block(h).await,
 			BlockRpc::NeedBlockQuery(h) => self.need_block(h).await.map(BlockRpc::NeedBlockReply),
 			_ => Err(Error::BadRpc("Unexpected RPC message".to_string())),
@@ -650,9 +746,7 @@ impl BlockManagerLocked {
 		hash: &Hash,
 		mgr: &BlockManager,
 	) -> Result<BlockStatus, Error> {
-		let path = mgr.block_path(hash);
-
-		let exists = fs::metadata(&path).await.is_ok();
+		let exists = mgr.is_block_compressed(hash).await.is_ok();
 		let needed = mgr.get_block_rc(hash)?;
 
 		Ok(BlockStatus { exists, needed })
@@ -661,16 +755,31 @@ impl BlockManagerLocked {
 	async fn write_block(
 		&self,
 		hash: &Hash,
-		data: &[u8],
+		data: &DataBlock,
 		mgr: &BlockManager,
 	) -> Result<BlockRpc, Error> {
+		let compressed = data.is_compressed();
+		let data = data.inner_buffer();
+
 		let mut path = mgr.block_dir(hash);
 		fs::create_dir_all(&path).await?;
 
 		path.push(hex::encode(hash));
-		if fs::metadata(&path).await.is_ok() {
-			return Ok(BlockRpc::Ok);
-		}
+		let to_delete = match (mgr.is_block_compressed(hash).await, compressed) {
+			(Ok(true), _) => return Ok(BlockRpc::Ok),
+			(Ok(false), false) => return Ok(BlockRpc::Ok),
+			(Ok(false), true) => {
+				let path_to_delete = path.clone();
+				path.set_extension("zst");
+				Some(path_to_delete)
+			}
+			(Err(_), compressed) => {
+				if compressed {
+					path.set_extension("zst");
+				}
+				None
+			}
+		};
 
 		let mut path2 = path.clone();
 		path2.set_extension("tmp");
@@ -679,6 +788,9 @@ impl BlockManagerLocked {
 		drop(f);
 
 		fs::rename(path2, path).await?;
+		if let Some(to_delete) = to_delete {
+			fs::remove_file(to_delete).await?;
+		}
 
 		Ok(BlockRpc::Ok)
 	}
@@ -688,9 +800,14 @@ impl BlockManagerLocked {
 			"Block {:?} is corrupted. Renaming to .corrupted and resyncing.",
 			hash
 		);
-		let path = mgr.block_path(hash);
+		let mut path = mgr.block_path(hash);
 		let mut path2 = path.clone();
-		path2.set_extension("corrupted");
+		if mgr.is_block_compressed(hash).await? {
+			path.set_extension("zst");
+			path2.set_extension("zst.corrupted");
+		} else {
+			path2.set_extension("corrupted");
+		}
 		fs::rename(path, path2).await?;
 		Ok(())
 	}
@@ -699,7 +816,10 @@ impl BlockManagerLocked {
 		let BlockStatus { exists, needed } = self.check_block_status(hash, mgr).await?;
 
 		if exists && needed.is_deletable() {
-			let path = mgr.block_path(hash);
+			let mut path = mgr.block_path(hash);
+			if mgr.is_block_compressed(hash).await? {
+				path.set_extension("zst");
+			}
 			fs::remove_file(path).await?;
 		}
 		Ok(())
@@ -806,3 +926,12 @@ impl RcEntry {
 		!self.is_deletable()
 	}
 }
+
+fn zstd_encode<R: std::io::Read>(mut source: R, level: i32) -> std::io::Result<Vec<u8>> {
+	let mut result = Vec::<u8>::new();
+	let mut encoder = Encoder::new(&mut result, level)?;
+	encoder.include_checksum(true)?;
+	std::io::copy(&mut source, &mut encoder)?;
+	encoder.finish()?;
+	Ok(result)
+}
diff --git a/src/util/config.rs b/src/util/config.rs
index 33802012..61a749e3 100644
--- a/src/util/config.rs
+++ b/src/util/config.rs
@@ -30,6 +30,13 @@ pub struct Config {
 	// (we can add more aliases for this later)
 	pub replication_mode: String,
 
+	/// Zstd compression level used on data blocks
+	#[serde(
+		deserialize_with = "deserialize_compression",
+		default = "default_compression"
+	)]
+	pub compression_level: Option<i32>,
+
 	/// RPC secret key: 32 bytes hex encoded
 	pub rpc_secret: String,
 
@@ -123,3 +130,57 @@ where
 
 	Ok(ret)
 }
+
+fn default_compression() -> Option<i32> {
+	Some(1)
+}
+
+fn deserialize_compression<'de, D>(deserializer: D) -> Result<Option<i32>, D::Error>
+where
+	D: de::Deserializer<'de>,
+{
+	use std::convert::TryFrom;
+
+	struct OptionVisitor;
+
+	impl<'de> serde::de::Visitor<'de> for OptionVisitor {
+		type Value = Option<i32>;
+		fn expecting(&self, formatter: &mut std::fmt::Formatter) -> std::fmt::Result {
+			formatter.write_str("int or 'none'")
+		}
+
+		fn visit_str<E>(self, value: &str) -> Result<Self::Value, E>
+		where
+			E: de::Error,
+		{
+			if value.eq_ignore_ascii_case("none") {
+				Ok(None)
+			} else {
+				Err(E::custom(format!(
+					"Invalid compression level: '{}', should be a number, or 'none'",
+					value
+				)))
+			}
+		}
+
+		fn visit_i64<E>(self, v: i64) -> Result<Self::Value, E>
+		where
+			E: de::Error,
+		{
+			i32::try_from(v)
+				.map(Some)
+				.map_err(|_| E::custom("Compression level out of bound".to_owned()))
+		}
+
+		fn visit_u64<E>(self, v: u64) -> Result<Self::Value, E>
+		where
+			E: de::Error,
+		{
+			i32::try_from(v)
+				.map(Some)
+				.map_err(|_| E::custom("Compression level out of bound".to_owned()))
+		}
+	}
+
+	deserializer.deserialize_any(OptionVisitor)
+}