diff --git a/plugins/repository-gcs/qa/google-cloud-storage/build.gradle b/plugins/repository-gcs/qa/google-cloud-storage/build.gradle
index d70c1921908f5..aef065cc8d92b 100644
--- a/plugins/repository-gcs/qa/google-cloud-storage/build.gradle
+++ b/plugins/repository-gcs/qa/google-cloud-storage/build.gradle
@@ -20,6 +20,7 @@
 
 import org.elasticsearch.gradle.MavenFilteringHack
 import org.elasticsearch.gradle.info.BuildParams
+import org.elasticsearch.gradle.test.RestIntegTestTask
 
 import java.nio.file.Files
 import java.security.KeyPair
@@ -117,9 +118,21 @@ task gcsThirdPartyTests {
   dependsOn check
 }
 
-integTest.mustRunAfter(thirdPartyTest)
 check.dependsOn thirdPartyTest
 
+integTest.mustRunAfter(thirdPartyTest)
+
+/*
+ * We only use a small amount of data in these tests, which means that the resumable upload path is not tested. We add
+ * an additional test that forces the large blob threshold to be small to exercise the resumable upload path.
+ */
+task largeBlobIntegTest(type: RestIntegTestTask) {
+  mustRunAfter(thirdPartyTest)
+}
+
+check.dependsOn integTest
+check.dependsOn largeBlobIntegTest
+
 Map<String, Object> expansions = [
   'bucket'   : gcsBucket,
   'base_path': gcsBasePath + "_integration_tests"
@@ -130,11 +143,15 @@ processTestResources {
   MavenFilteringHack.filter(it, expansions)
 }
 
-integTest {
+final Closure integTestConfiguration = {
   dependsOn project(':plugins:repository-gcs').bundlePlugin
 }
 
-testClusters.integTest {
+integTest integTestConfiguration
+
+largeBlobIntegTest integTestConfiguration
+
+final Closure testClustersConfiguration = {
   plugin project(':plugins:repository-gcs').bundlePlugin.archiveFile
 
   keystore 'gcs.client.integration_test.credentials_file', serviceAccountFile, IGNORE_VALUE
@@ -148,3 +165,11 @@ testClusters.integTest {
     println "Using an external service to test the repository-gcs plugin"
   }
 }
+
+testClusters.integTest testClustersConfiguration
+
+testClusters.largeBlobIntegTest testClustersConfiguration
+testClusters.largeBlobIntegTest {
+  // force large blob uploads by setting the threshold small, forcing this code path to be tested
+  systemProperty 'es.repository_gcs.large_blob_threshold_byte_size', '256'
+}
diff --git a/plugins/repository-gcs/src/main/java/org/elasticsearch/repositories/gcs/GoogleCloudStorageBlobStore.java b/plugins/repository-gcs/src/main/java/org/elasticsearch/repositories/gcs/GoogleCloudStorageBlobStore.java
index 134c9fc3519fc..47b942de10da2 100644
--- a/plugins/repository-gcs/src/main/java/org/elasticsearch/repositories/gcs/GoogleCloudStorageBlobStore.java
+++ b/plugins/repository-gcs/src/main/java/org/elasticsearch/repositories/gcs/GoogleCloudStorageBlobStore.java
@@ -21,6 +21,7 @@
 
 import com.google.api.gax.paging.Page;
 import com.google.cloud.BatchResult;
+import com.google.cloud.WriteChannel;
 import com.google.cloud.storage.Blob;
 import com.google.cloud.storage.BlobId;
 import com.google.cloud.storage.BlobInfo;
@@ -33,6 +34,7 @@
 import org.apache.logging.log4j.Logger;
 import org.apache.logging.log4j.message.ParameterizedMessage;
 import org.elasticsearch.ExceptionsHelper;
+import org.elasticsearch.common.SuppressForbidden;
 import org.elasticsearch.common.blobstore.BlobContainer;
 import org.elasticsearch.common.blobstore.BlobMetadata;
 import org.elasticsearch.common.blobstore.BlobPath;
@@ -41,11 +43,15 @@
 import org.elasticsearch.common.blobstore.DeleteResult;
 import org.elasticsearch.common.blobstore.support.PlainBlobMetadata;
 import org.elasticsearch.common.collect.MapBuilder;
+import org.elasticsearch.common.unit.ByteSizeUnit;
+import org.elasticsearch.common.unit.ByteSizeValue;
 import org.elasticsearch.core.internal.io.Streams;
 
 import java.io.IOException;
 import java.io.InputStream;
+import java.nio.ByteBuffer;
 import java.nio.channels.Channels;
+import java.nio.channels.WritableByteChannel;
 import java.nio.file.FileAlreadyExistsException;
 import java.util.ArrayList;
 import java.util.Collection;
@@ -68,7 +74,26 @@ class GoogleCloudStorageBlobStore implements BlobStore {
     // request. Larger files should be uploaded over multiple requests (this is
     // called "resumable upload")
     // https://cloud.google.com/storage/docs/json_api/v1/how-tos/resumable-upload
-    public static final int LARGE_BLOB_THRESHOLD_BYTE_SIZE = 5 * 1024 * 1024;
+    public static final int LARGE_BLOB_THRESHOLD_BYTE_SIZE;
+
+    static {
+        final String key = "es.repository_gcs.large_blob_threshold_byte_size";
+        final String largeBlobThresholdByteSizeProperty = System.getProperty(key);
+        if (largeBlobThresholdByteSizeProperty == null) {
+            LARGE_BLOB_THRESHOLD_BYTE_SIZE = Math.toIntExact(new ByteSizeValue(5, ByteSizeUnit.MB).getBytes());
+        } else {
+            final int largeBlobThresholdByteSize;
+            try {
+              largeBlobThresholdByteSize = Integer.parseInt(largeBlobThresholdByteSizeProperty);
+            } catch (final NumberFormatException e) {
+                throw new IllegalArgumentException("failed to parse " + key + " having value [" + largeBlobThresholdByteSizeProperty + "]");
+            }
+            if (largeBlobThresholdByteSize <= 0) {
+                throw new IllegalArgumentException(key + " must be positive but was [" + largeBlobThresholdByteSizeProperty + "]");
+            }
+            LARGE_BLOB_THRESHOLD_BYTE_SIZE = largeBlobThresholdByteSize;
+        }
+    }
 
     private final String bucketName;
     private final String clientName;
@@ -212,8 +237,30 @@ private void writeBlobResumable(BlobInfo blobInfo, InputStream inputStream, bool
             new Storage.BlobWriteOption[]{Storage.BlobWriteOption.doesNotExist()} : new Storage.BlobWriteOption[0];
         for (int retry = 0; retry < 3; ++retry) {
             try {
-                SocketAccess.doPrivilegedVoidIOException(() ->
-                    Streams.copy(inputStream, Channels.newOutputStream(client().writer(blobInfo, writeOptions))));
+                final WriteChannel writeChannel = SocketAccess.doPrivilegedIOException(() -> client().writer(blobInfo, writeOptions));
+                /*
+                 * It is not enough to wrap the call to Streams#copy, we have to wrap the privileged calls too; this is because Streams#copy
+                 * is in the stacktrace and is not granted the permissions needed to close and write the channel.
+                 */
+                Streams.copy(inputStream, Channels.newOutputStream(new WritableByteChannel() {
+
+                    @SuppressForbidden(reason = "channel is based on a socket")
+                    @Override
+                    public int write(final ByteBuffer src) throws IOException {
+                        return SocketAccess.doPrivilegedIOException(() -> writeChannel.write(src));
+                    }
+
+                    @Override
+                    public boolean isOpen() {
+                        return writeChannel.isOpen();
+                    }
+
+                    @Override
+                    public void close() throws IOException {
+                        SocketAccess.doPrivilegedVoidIOException(writeChannel::close);
+                    }
+
+                }));
                 return;
             } catch (final StorageException se) {
                 final int errorCode = se.getCode();