diff --git a/src/os/bluestore/BlueFS.h b/src/os/bluestore/BlueFS.h
index 72ffd3ff9ba..fbcb0bbbf77 100644
--- a/src/os/bluestore/BlueFS.h
+++ b/src/os/bluestore/BlueFS.h
@@ -5,6 +5,7 @@
 
 #include <atomic>
 #include <mutex>
+#include <limits>
 
 #include "bluefs_types.h"
 #include "blk/BlockDevice.h"
@@ -206,15 +207,21 @@ public:
     // to use buffer_appender exclusively here (e.g., it's notion of
     // offset will remain accurate).
     void append(const char *buf, size_t len) {
+      uint64_t l0 = get_buffer_length();
+      ceph_assert(l0 + len <= std::numeric_limits<unsigned>::max());
       buffer_appender.append(buf, len);
     }
 
     // note: used internally only, for ino 1 or 0.
     void append(ceph::buffer::list& bl) {
+      uint64_t l0 = get_buffer_length();
+      ceph_assert(l0 + bl.length() <= std::numeric_limits<unsigned>::max());
       buffer.claim_append(bl);
     }
 
     void append_zero(size_t len) {
+      uint64_t l0 = get_buffer_length();
+      ceph_assert(l0 + len <= std::numeric_limits<unsigned>::max());
       buffer_appender.append_zero(len);
     }
 
@@ -564,9 +571,25 @@ public:
     int r = _flush(h, force, l);
     ceph_assert(r == 0);
   }
-  void try_flush(FileWriter *h) {
-    if (h->get_buffer_length() >= cct->_conf->bluefs_min_flush_size) {
-      flush(h, true);
+
+  void append_try_flush(FileWriter *h, const char* buf, size_t len) {
+    size_t max_size = 1ull << 30; // cap to 1GB
+    while (len > 0) {
+      bool need_flush = true;
+      auto l0 = h->get_buffer_length();
+      if (l0 < max_size) {
+	size_t l = std::min(len, max_size - l0);
+	h->append(buf, l);
+	buf += l;
+	len -= l;
+	need_flush = h->get_buffer_length() >= cct->_conf->bluefs_min_flush_size;
+      }
+      if (need_flush) {
+	flush(h, true);
+	// make sure we've made any progress with flush hence the
+	// loop doesn't iterate forever
+	ceph_assert(h->get_buffer_length() < max_size);
+      }
     }
   }
   void flush_range(FileWriter *h, uint64_t offset, uint64_t length) {
diff --git a/src/os/bluestore/BlueRocksEnv.cc b/src/os/bluestore/BlueRocksEnv.cc
index 71232b3f65f..6327fb1e8a3 100644
--- a/src/os/bluestore/BlueRocksEnv.cc
+++ b/src/os/bluestore/BlueRocksEnv.cc
@@ -173,10 +173,7 @@ class BlueRocksWritableFile : public rocksdb::WritableFile {
     }*/
 
   rocksdb::Status Append(const rocksdb::Slice& data) override {
-    h->append(data.data(), data.size());
-    // Avoid calling many time Append() and then calling Flush().
-    // Especially for buffer mode, flush much data will cause jitter.
-    fs->try_flush(h);
+    fs->append_try_flush(h, data.data(), data.size());
     return rocksdb::Status::OK();
   }
 
diff --git a/src/test/objectstore/test_bluefs.cc b/src/test/objectstore/test_bluefs.cc
index 4bbd2e6dd04..394a8e9862a 100644
--- a/src/test/objectstore/test_bluefs.cc
+++ b/src/test/objectstore/test_bluefs.cc
@@ -171,7 +171,7 @@ TEST(BlueFS, small_appends) {
 
 TEST(BlueFS, very_large_write) {
   // we'll write a ~5G file, so allocate more than that for the whole fs
-  uint64_t size = 1048576 * 1024 * 8ull;
+  uint64_t size = 1048576 * 1024 * 6ull;
   TempBdev bdev{size};
   BlueFS fs(g_ceph_context);
 
@@ -243,6 +243,59 @@ TEST(BlueFS, very_large_write) {
   g_ceph_context->_conf.set_val("bluefs_buffered_io", stringify((int)old));
 }
 
+TEST(BlueFS, very_large_write2) {
+  // we'll write a ~5G file, so allocate more than that for the whole fs
+  uint64_t size_full = 1048576 * 1024 * 6ull;
+  uint64_t size = 1048576 * 1024 * 5ull;
+  TempBdev bdev{ size_full };
+  BlueFS fs(g_ceph_context);
+
+  bool old = g_ceph_context->_conf.get_val<bool>("bluefs_buffered_io");
+  g_ceph_context->_conf.set_val("bluefs_buffered_io", "false");
+  uint64_t total_written = 0;
+
+  ASSERT_EQ(0, fs.add_block_device(BlueFS::BDEV_DB, bdev.path, false, 1048576));
+  uuid_d fsid;
+  ASSERT_EQ(0, fs.mkfs(fsid, { BlueFS::BDEV_DB, false, false }));
+  ASSERT_EQ(0, fs.mount());
+  ASSERT_EQ(0, fs.maybe_verify_layout({ BlueFS::BDEV_DB, false, false }));
+
+  char fill_arr[1 << 20]; // 1M
+  for (size_t i = 0; i < sizeof(fill_arr); ++i) {
+    fill_arr[i] = (char)i;
+  }
+  std::unique_ptr<char[]> buf;
+  buf.reset(new char[size]);
+  for (size_t i = 0; i < size; i += sizeof(fill_arr)) {
+    memcpy(buf.get() + i, fill_arr, sizeof(fill_arr));
+  }
+  {
+    BlueFS::FileWriter* h;
+    ASSERT_EQ(0, fs.mkdir("dir"));
+    ASSERT_EQ(0, fs.open_for_write("dir", "bigfile", &h, false));
+    fs.append_try_flush(h, buf.get(), size);
+    total_written = size;
+    fs.fsync(h);
+    fs.close_writer(h);
+  }
+  memset(buf.get(), 0, size);
+  {
+    BlueFS::FileReader* h;
+    ASSERT_EQ(0, fs.open_for_read("dir", "bigfile", &h));
+    ASSERT_EQ(h->file->fnode.size, total_written);
+    auto l = h->file->fnode.size;
+    int64_t r = fs.read(h, 0, l, NULL, buf.get());
+    ASSERT_EQ(r, l);
+    for (size_t i = 0; i < size; i += sizeof(fill_arr)) {
+      ceph_assert(memcmp(buf.get() + i, fill_arr, sizeof(fill_arr)) == 0);
+    }
+    delete h;
+  }
+  fs.umount();
+
+  g_ceph_context->_conf.set_val("bluefs_buffered_io", stringify((int)old));
+}
+
 #define ALLOC_SIZE 4096
 
 void write_data(BlueFS &fs, uint64_t rationed_bytes)