diff --git a/datman/src/commands/backup.rs b/datman/src/commands/backup.rs
index 4e8058c..95a4655 100644
--- a/datman/src/commands/backup.rs
+++ b/datman/src/commands/backup.rs
@@ -28,6 +28,7 @@ use std::fmt::Debug;
 use std::io::Write;
 use std::path::Path;
 use std::process::{Child, Command, Stdio};
+use std::sync::Arc;
 use yama::chunking::SENSIBLE_THRESHOLD;
 use yama::commands::{load_pile_descriptor, open_pile, store_tree_node};
 use yama::definitions::{
@@ -194,7 +195,7 @@ pub fn backup_source_to_destination<PT: ProgressTracker>(
 
             info!("Storing using yama.");
             yama::operations::storing::store_fully(
-                &pile,
+                Arc::new(pile),
                 &absolute_source_path,
                 &pointer_name,
                 root,
diff --git a/datman/src/remote/backup_source_responder.rs b/datman/src/remote/backup_source_responder.rs
index bb7ed7f..65cf394 100644
--- a/datman/src/remote/backup_source_responder.rs
+++ b/datman/src/remote/backup_source_responder.rs
@@ -7,6 +7,7 @@ use crossbeam_channel::Sender;
 use log::info;
 use std::io::{stdin, stdout, Read, Write};
 use std::path::PathBuf;
+use std::sync::Arc;
 use std::time::Instant;
 use yama::definitions::TreeNode;
 use yama::pile::{Pile, RawPile};
@@ -63,7 +64,7 @@ pub fn chunking<R: Read + Send + 'static, W: Write + Send + 'static>(
     let progress_bar = &mut ();
 
     yama::operations::storing::store_fully(
-        &pile,
+        Arc::new(pile),
         &path,
         &pointer_name,
         tree_node,
@@ -161,7 +162,7 @@ pub fn chunking_stdio() -> anyhow::Result<()> {
         let pile = Pile::new(raw_pile);
 
         yama::operations::storing::store_fully(
-            &pile,
+            Arc::new(pile),
             &path,
             &pointer_name,
             tree_node,
diff --git a/yama/src/operations/storing.rs b/yama/src/operations/storing.rs
index f536938..aa8e78f 100644
--- a/yama/src/operations/storing.rs
+++ b/yama/src/operations/storing.rs
@@ -30,10 +30,12 @@ use crate::chunking::{ChunkSubmissionTarget, RecursiveChunker, SENSIBLE_THRESHOL
 use crate::commands;
 use crate::commands::{fully_integrate_pointer_node, retrieve_tree_node};
 use crate::definitions::{PointerData, RecursiveChunkRef, RootTreeNode, TreeNode};
-use crate::pile::{Pile, RawPile, StoragePipelineSettings};
+use crate::pile::{existence_checker_stage, Pile, RawPile, StoragePipelineSettings};
 use crate::progress::ProgressTracker;
 use crate::tree::{create_uidgid_lookup_tables, differentiate_node_in_place};
+use crate::utils::get_number_of_workers;
 use std::collections::BTreeMap;
+use std::sync::Arc;
 
 pub fn store<CST: ChunkSubmissionTarget, PT: ProgressTracker>(
     root_path: &Path,
@@ -231,7 +233,7 @@ pub fn manager<PT: ProgressTracker>(
 /// loaded and fully-integrated).
 /// This also creates a pointer (which is why this is called `store_fully`).
 pub fn store_fully<PT: ProgressTracker>(
-    pile: &Pile<Box<dyn RawPile>>,
+    pile: Arc<Pile<Box<dyn RawPile>>>,
     root_dir: &PathBuf,
     new_pointer_name: &String,
     mut root_node: TreeNode,
@@ -256,12 +258,14 @@ pub fn store_fully<PT: ProgressTracker>(
     if use_pipelined_storage {
         // TODO make these configurable
         let sps = StoragePipelineSettings {
-            num_compressors: num_cpus::get() as u32,
+            num_compressors: get_number_of_workers("YAMA_PL_COMPRESSORS") as u32,
             compressor_input_bound: 64,
             writer_input_bound: 64,
         };
         let (control_tx, control_rx) = crossbeam_channel::unbounded();
+        let pile2 = pile.clone();
         let pipeline = pile.raw_pile.build_storage_pipeline(sps, control_tx)?;
+        let pipeline = existence_checker_stage(pile2, pipeline);
         store(
             &root_dir,
             &mut root_node,
@@ -270,7 +274,13 @@ pub fn store_fully<PT: ProgressTracker>(
             num_workers,
         )?;
     } else {
-        store(&root_dir, &mut root_node, pile, progress_bar, num_workers)?;
+        store(
+            &root_dir,
+            &mut root_node,
+            pile.as_ref(),
+            progress_bar,
+            num_workers,
+        )?;
     }
 
     let mut uid_lookup = BTreeMap::new();
diff --git a/yama/src/pile.rs b/yama/src/pile.rs
index 0f99fd9..a2e2fb4 100644
--- a/yama/src/pile.rs
+++ b/yama/src/pile.rs
@@ -20,6 +20,7 @@ use std::path::PathBuf;
 use serde::{Deserialize, Serialize};
 
 use crate::definitions::{ChunkId, PointerData};
+use crate::utils::get_number_of_workers;
 use crossbeam_channel::Sender;
 use std::collections::HashSet;
 use std::fmt::Debug;
@@ -82,6 +83,30 @@ pub struct StoragePipelineSettings {
     pub writer_input_bound: u32,
 }
 
+pub fn existence_checker_stage<RP: RawPile>(
+    pile: Arc<Pile<RP>>,
+    next_stage: Sender<(ChunkId, Vec<u8>)>,
+) -> Sender<(ChunkId, Vec<u8>)> {
+    let (tx, rx) = crossbeam_channel::bounded::<(ChunkId, Vec<u8>)>(32);
+
+    // TODO would like something better for the networked case
+    for _ in 0..get_number_of_workers("YAMA_EXISTENCE_CHECKERS") {
+        let next_stage = next_stage.clone();
+        let rx = rx.clone();
+        let pile = pile.clone();
+        std::thread::spawn(move || {
+            while let Ok((chunk_id, chunk)) = rx.recv() {
+                // TODO handle errors properly
+                if !pile.chunk_exists(&chunk_id).unwrap() {
+                    next_stage.send((chunk_id, chunk)).unwrap();
+                }
+            }
+        });
+    }
+
+    tx
+}
+
 pub enum ControllerMessage {
     Failure {
         worker_id: Arc<String>,
diff --git a/yama/src/remote/responder.rs b/yama/src/remote/responder.rs
index 748d65b..3786029 100644
--- a/yama/src/remote/responder.rs
+++ b/yama/src/remote/responder.rs
@@ -198,7 +198,9 @@ impl Responder {
                     {
                         let mut chunk_id = ChunkId::default();
                         chunk_id.copy_from_slice(&key[..]);
-                        writing_pipeline.pipeline_submission.send((chunk_id, value));
+                        writing_pipeline
+                            .pipeline_submission
+                            .send((chunk_id, value))?;
                         // We lie and say it was successful once we submit.
                         // We'll complain on our side if anything goes wrong, anyway.
                         Response {