diff --git a/CMakeLists.txt b/CMakeLists.txt
index 4432b264a13..6c3c77f849b 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -617,6 +617,7 @@ set(SOURCES
         env/env_encryption.cc
         env/env_hdfs.cc
         env/file_system.cc
+        env/file_system_tracer.cc
         env/mock_env.cc
         file/delete_scheduler.cc
         file/file_prefetch_buffer.cc
@@ -719,6 +720,7 @@ set(SOURCES
         tools/trace_analyzer_tool.cc
         trace_replay/trace_replay.cc
         trace_replay/block_cache_tracer.cc
+        trace_replay/io_tracer.cc
         util/coding.cc
         util/compaction_job_stats_impl.cc
         util/comparator.cc
@@ -995,7 +997,7 @@ if(WITH_TESTS OR WITH_BENCHMARK_TOOLS)
   test_util/testharness.cc)
   target_link_libraries(testharness gtest)
 endif()
-  
+
 if(WITH_TESTS)
   set(TESTS
         db/db_basic_test.cc
diff --git a/db/db_impl/db_impl.cc b/db/db_impl/db_impl.cc
index b95d85a4495..65a5569105b 100644
--- a/db/db_impl/db_impl.cc
+++ b/db/db_impl/db_impl.cc
@@ -150,6 +150,7 @@ DBImpl::DBImpl(const DBOptions& options, const std::string& dbname,
       own_info_log_(options.info_log == nullptr),
       initial_db_options_(SanitizeOptions(dbname, options)),
       env_(initial_db_options_.env),
+      io_tracer_(std::make_shared<IOTracer>()),
       fs_(initial_db_options_.env->GetFileSystem()),
       immutable_db_options_(initial_db_options_),
       mutable_db_options_(initial_db_options_),
@@ -3044,6 +3045,20 @@ FileSystem* DBImpl::GetFileSystem() const {
   return immutable_db_options_.fs.get();
 }
 
+#ifndef ROCKSDB_LITE
+
+Status DBImpl::StartIOTrace(Env* env, const TraceOptions& trace_options,
+                            std::unique_ptr<TraceWriter>&& trace_writer) {
+  return io_tracer_->StartIOTrace(env, trace_options, std::move(trace_writer));
+}
+
+Status DBImpl::EndIOTrace() {
+  io_tracer_->EndIOTrace();
+  return Status::OK();
+}
+
+#endif  // ROCKSDB_LITE
+
 Options DBImpl::GetOptions(ColumnFamilyHandle* column_family) const {
   InstrumentedMutexLock l(&mutex_);
   auto cfh = static_cast_with_check<ColumnFamilyHandleImpl>(column_family);
diff --git a/db/db_impl/db_impl.h b/db/db_impl/db_impl.h
index 13dc575ccd8..09c10496a4b 100644
--- a/db/db_impl/db_impl.h
+++ b/db/db_impl/db_impl.h
@@ -55,6 +55,7 @@
 #include "rocksdb/write_buffer_manager.h"
 #include "table/scoped_arena_iterator.h"
 #include "trace_replay/block_cache_tracer.h"
+#include "trace_replay/io_tracer.h"
 #include "trace_replay/trace_replay.h"
 #include "util/autovector.h"
 #include "util/hash.h"
@@ -445,6 +446,13 @@ class DBImpl : public DB {
   using DB::EndBlockCacheTrace;
   Status EndBlockCacheTrace() override;
 
+  using DB::StartIOTrace;
+  Status StartIOTrace(Env* env, const TraceOptions& options,
+                      std::unique_ptr<TraceWriter>&& trace_writer) override;
+
+  using DB::EndIOTrace;
+  Status EndIOTrace() override;
+
   using DB::GetPropertiesOfAllTables;
   virtual Status GetPropertiesOfAllTables(
       ColumnFamilyHandle* column_family,
@@ -1003,6 +1011,7 @@ class DBImpl : public DB {
   bool own_info_log_;
   const DBOptions initial_db_options_;
   Env* const env_;
+  std::shared_ptr<IOTracer> io_tracer_;
   std::shared_ptr<FileSystem> fs_;
   const ImmutableDBOptions immutable_db_options_;
   MutableDBOptions mutable_db_options_;
diff --git a/env/composite_env_wrapper.h b/env/composite_env_wrapper.h
index 8a8e2f266c8..f12657a04b2 100644
--- a/env/composite_env_wrapper.h
+++ b/env/composite_env_wrapper.h
@@ -613,6 +613,11 @@ class CompositeEnvWrapper : public Env {
     return file_system_->OptimizeForCompactionTableRead(
         FileOptions(env_options), db_options);
   }
+
+  // This seems to clash with a macro on Windows, so #undef it here
+#ifdef GetFreeSpace
+#undef GetFreeSpace
+#endif
   Status GetFreeSpace(const std::string& path, uint64_t* diskfree) override {
     IOOptions io_opts;
     IODebugContext dbg;
@@ -1089,6 +1094,11 @@ class LegacyFileSystemWrapper : public FileSystem {
       const ImmutableDBOptions& db_options) const override {
     return target_->OptimizeForCompactionTableRead(file_options, db_options);
   }
+
+// This seems to clash with a macro on Windows, so #undef it here
+#ifdef GetFreeSpace
+#undef GetFreeSpace
+#endif
   IOStatus GetFreeSpace(const std::string& path, const IOOptions& /*options*/,
                         uint64_t* diskfree, IODebugContext* /*dbg*/) override {
     return status_to_io_status(target_->GetFreeSpace(path, diskfree));
diff --git a/env/file_system_tracer.h b/env/file_system_tracer.h
index f5c92e54c85..6899549b863 100644
--- a/env/file_system_tracer.h
+++ b/env/file_system_tracer.h
@@ -72,9 +72,6 @@ class FileSystemPtr {
         fs_tracer_(
             std::make_shared<FileSystemTracingWrapper>(fs_, io_tracer_)) {}
 
-  explicit FileSystemPtr(std::shared_ptr<FileSystem> fs)
-      : fs_(fs), io_tracer_(nullptr), fs_tracer_(nullptr) {}
-
   std::shared_ptr<FileSystem> operator->() const {
     if (io_tracer_ && io_tracer_->is_tracing_enabled()) {
       return fs_tracer_;
diff --git a/include/rocksdb/db.h b/include/rocksdb/db.h
index 5d69a2a0220..498d81d6ef8 100644
--- a/include/rocksdb/db.h
+++ b/include/rocksdb/db.h
@@ -1587,6 +1587,16 @@ class DB {
     return Status::NotSupported("EndTrace() is not implemented.");
   }
 
+  // StartIOTrace and EndIOTrace are experimental. They are not enabled yet.
+  virtual Status StartIOTrace(Env* /*env*/, const TraceOptions& /*options*/,
+                              std::unique_ptr<TraceWriter>&& /*trace_writer*/) {
+    return Status::NotSupported("StartTrace() is not implemented.");
+  }
+
+  virtual Status EndIOTrace() {
+    return Status::NotSupported("StartTrace() is not implemented.");
+  }
+
   // Trace block cache accesses. Use EndBlockCacheTrace() to stop tracing.
   virtual Status StartBlockCacheTrace(
       const TraceOptions& /*options*/,
diff --git a/trace_replay/io_tracer.cc b/trace_replay/io_tracer.cc
index fde7eb6d0b0..b1ae8f222bc 100644
--- a/trace_replay/io_tracer.cc
+++ b/trace_replay/io_tracer.cc
@@ -52,7 +52,7 @@ Status IOTraceWriter::WriteIOOp(const IOTraceRecord& record) {
       PutFixed64(&trace.payload, record.offset);
       FALLTHROUGH_INTENDED;
     case TraceType::kIOLen:
-      trace.payload.push_back(record.len);
+      PutFixed64(&trace.payload, record.len);
       break;
     default:
       assert(false);
@@ -177,13 +177,10 @@ Status IOTraceReader::ReadIOOp(IOTraceRecord* record) {
       }
       FALLTHROUGH_INTENDED;
     case TraceType::kIOLen: {
-      if (enc_slice.empty()) {
+      if (!GetFixed64(&enc_slice, &record->len)) {
         return Status::Incomplete(
             "Incomplete access record: Failed to read length.");
       }
-      record->len = static_cast<size_t>(enc_slice[0]);
-      const unsigned int kCharSize = 1;
-      enc_slice.remove_prefix(kCharSize);
       break;
     }
     default:
diff --git a/trace_replay/io_tracer.h b/trace_replay/io_tracer.h
index 9a793d05d62..4681ff54c47 100644
--- a/trace_replay/io_tracer.h
+++ b/trace_replay/io_tracer.h
@@ -25,7 +25,7 @@ struct IOTraceRecord {
   std::string io_status;
   // Required fields for read.
   std::string file_name;
-  size_t len = 0;
+  uint64_t len = 0;
   uint64_t offset = 0;
   uint64_t file_size = 0;
 
diff --git a/trace_replay/io_tracer_test.cc b/trace_replay/io_tracer_test.cc
index c83be285ad2..3e1602ea167 100644
--- a/trace_replay/io_tracer_test.cc
+++ b/trace_replay/io_tracer_test.cc
@@ -31,7 +31,7 @@ class IOTracerTest : public testing::Test {
     EXPECT_OK(env_->DeleteDir(test_path_));
   }
 
-  std::string GetFileOperation(uint32_t id) {
+  std::string GetFileOperation(uint64_t id) {
     id = id % 4;
     switch (id) {
       case 0:
@@ -42,13 +42,15 @@ class IOTracerTest : public testing::Test {
         return "FileSize";
       case 3:
         return "DeleteDir";
+      default:
+        assert(false);
     }
-    assert(false);
+    return "";
   }
 
-  void WriteIOOp(IOTraceWriter* writer, uint32_t nrecords) {
+  void WriteIOOp(IOTraceWriter* writer, uint64_t nrecords) {
     assert(writer);
-    for (uint32_t i = 0; i < nrecords; i++) {
+    for (uint64_t i = 0; i < nrecords; i++) {
       IOTraceRecord record;
       record.trace_type = TraceType::kIOLenAndOffset;
       record.file_operation = GetFileOperation(i);
@@ -100,8 +102,8 @@ TEST_F(IOTracerTest, AtomicWrite) {
     IOTraceReader reader(std::move(trace_reader));
     IOTraceHeader header;
     ASSERT_OK(reader.ReadHeader(&header));
-    ASSERT_EQ(kMajorVersion, header.rocksdb_major_version);
-    ASSERT_EQ(kMinorVersion, header.rocksdb_minor_version);
+    ASSERT_EQ(kMajorVersion, static_cast<int>(header.rocksdb_major_version));
+    ASSERT_EQ(kMinorVersion, static_cast<int>(header.rocksdb_minor_version));
     // Read record and verify data.
     IOTraceRecord access_record;
     ASSERT_OK(reader.ReadIOOp(&access_record));
@@ -162,8 +164,8 @@ TEST_F(IOTracerTest, AtomicNoWriteAfterEndTrace) {
     IOTraceReader reader(std::move(trace_reader));
     IOTraceHeader header;
     ASSERT_OK(reader.ReadHeader(&header));
-    ASSERT_EQ(kMajorVersion, header.rocksdb_major_version);
-    ASSERT_EQ(kMinorVersion, header.rocksdb_minor_version);
+    ASSERT_EQ(kMajorVersion, static_cast<int>(header.rocksdb_major_version));
+    ASSERT_EQ(kMinorVersion, static_cast<int>(header.rocksdb_minor_version));
 
     IOTraceRecord access_record;
     ASSERT_OK(reader.ReadIOOp(&access_record));
@@ -196,8 +198,8 @@ TEST_F(IOTracerTest, AtomicMultipleWrites) {
     IOTraceReader reader(std::move(trace_reader));
     IOTraceHeader header;
     ASSERT_OK(reader.ReadHeader(&header));
-    ASSERT_EQ(kMajorVersion, header.rocksdb_major_version);
-    ASSERT_EQ(kMinorVersion, header.rocksdb_minor_version);
+    ASSERT_EQ(kMajorVersion, static_cast<int>(header.rocksdb_major_version));
+    ASSERT_EQ(kMinorVersion, static_cast<int>(header.rocksdb_minor_version));
     // Read 10 records.
     VerifyIOOp(&reader, 10);
     // Read one more and record and it should report error.