diff --git a/adapter/include/hermes/adapter/mpiio.h b/adapter/include/hermes/adapter/mpiio.h
index 705e5cf83..97755f644 100644
--- a/adapter/include/hermes/adapter/mpiio.h
+++ b/adapter/include/hermes/adapter/mpiio.h
@@ -33,12 +33,14 @@
 /**
  * Internal headers
  */
-#include <bucket.h>
 #include <hermes.h>
+#include <bucket.h>
+#include <vbucket.h>
+
+#include <hermes/adapter/constants.h>
+#include <hermes/adapter/singleton.h>
 #include <hermes/adapter/interceptor.h>
 #include <hermes/adapter/mpiio/mapper/mapper_factory.h>
-#include <hermes/adapter/singleton.h>
-#include <vbucket.h>
 
 #include <hermes/adapter/interceptor.cc>
 #include <hermes/adapter/mpiio/metadata_manager.cc>
diff --git a/adapter/include/hermes/adapter/posix.h b/adapter/include/hermes/adapter/posix.h
index 4dfdcfc39..f5d8d4b94 100644
--- a/adapter/include/hermes/adapter/posix.h
+++ b/adapter/include/hermes/adapter/posix.h
@@ -28,15 +28,17 @@
 /**
  * Internal headers
  */
-#include <bucket.h>
 #include <hermes.h>
+#include <bucket.h>
+#include <vbucket.h>
+
+#include <hermes/adapter/constants.h>
 #include <hermes/adapter/interceptor.h>
+#include <hermes/adapter/singleton.h>
 #include <hermes/adapter/posix/common/constants.h>
 #include <hermes/adapter/posix/common/datastructures.h>
 #include <hermes/adapter/posix/mapper/mapper_factory.h>
 #include <hermes/adapter/posix/metadata_manager.h>
-#include <hermes/adapter/singleton.h>
-#include <vbucket.h>
 
 /**
  * Function declarations
diff --git a/adapter/include/hermes/adapter/stdio.h b/adapter/include/hermes/adapter/stdio.h
index 1e5210e60..4f5021d43 100644
--- a/adapter/include/hermes/adapter/stdio.h
+++ b/adapter/include/hermes/adapter/stdio.h
@@ -33,6 +33,7 @@
  */
 #include <bucket.h>
 #include <hermes.h>
+#include <hermes/adapter/constants.h>
 #include <hermes/adapter/interceptor.h>
 #include <hermes/adapter/singleton.h>
 #include <hermes/adapter/stdio/common/constants.h>
diff --git a/adapter/src/hermes/adapter/constants.h b/adapter/src/hermes/adapter/constants.h
index 83ed19335..2c8ee8b35 100644
--- a/adapter/src/hermes/adapter/constants.h
+++ b/adapter/src/hermes/adapter/constants.h
@@ -13,6 +13,8 @@
 #ifndef HERMES_ADAPTER_CONSTANTS_H
 #define HERMES_ADAPTER_CONSTANTS_H
 
+#include <glog/logging.h>
+
 /**
  * Constants file for all adapter.
  * This file contains common constants across different adapters.
@@ -88,4 +90,40 @@ const char* kAdapterScratchMode = "SCRATCH";
  * Default value: \c 1
  */
 const char* kStopDaemon = "HERMES_STOP_DAEMON";
+
+/**
+ * The page size in bytes when mapping files to Hermes Blobs. Hermes will be
+ * more efficient if you set this number to the most common size of writes in
+ * your application. This is set via HERMES_PAGE_SIZE.
+ *
+ * Example: With a page size of 1MiB, a 100 MiB file will be mapped to 100, 1MiB
+ * Blobs. In this scenario, doing several smaller writes within the same 1MiB
+ * region will cause all of those writes to transfer 1MiB of data, which is why
+ * it's important to align the page size to your workload.
+ */
+const size_t kPageSize = []() {
+  const char *kPageSizeVar = "HERMES_PAGE_SIZE";
+  const size_t kDefaultPageSize = 1 * 1024 * 1024;
+
+  size_t result = kDefaultPageSize;
+  char *page_size = getenv(kPageSizeVar);
+
+  if (page_size) {
+    result = (size_t)std::strtoull(page_size, NULL, 0);
+    if (result == 0) {
+      LOG(FATAL) << "Invalid value of " << kPageSizeVar << ": " << page_size;
+    }
+  }
+
+  LOG(INFO) << "Adapter page size: " << result << "\n";
+
+  return result;
+}();
+
+/**
+ * Set this environment variable to '1' for more efficient performance on
+ * workloads that are write-only.
+ */
+const char* kHermesWriteOnlyVar = "HERMES_WRITE_ONLY";
+
 #endif  // HERMES_ADAPTER_CONSTANTS_H
diff --git a/adapter/src/hermes/adapter/interceptor.h b/adapter/src/hermes/adapter/interceptor.h
index 678c034d9..221e357ac 100644
--- a/adapter/src/hermes/adapter/interceptor.h
+++ b/adapter/src/hermes/adapter/interceptor.h
@@ -24,7 +24,6 @@
 #include <regex>
 
 #include <buffer_pool_internal.h>
-#include <hermes/adapter/constants.h>
 #include <hermes/adapter/enumerations.h>
 #include <hermes/adapter/singleton.h>
 
diff --git a/adapter/src/hermes/adapter/mpiio/CMakeLists.txt b/adapter/src/hermes/adapter/mpiio/CMakeLists.txt
index 5b28cad54..6efe010ee 100644
--- a/adapter/src/hermes/adapter/mpiio/CMakeLists.txt
+++ b/adapter/src/hermes/adapter/mpiio/CMakeLists.txt
@@ -17,18 +17,11 @@ set(MPIIO_ADAPTER_PRIVATE_HEADER ${CMAKE_CURRENT_SOURCE_DIR}/metadata_manager.h
         ${CMAKE_CURRENT_SOURCE_DIR}/common/enumerations.h
         ${CMAKE_CURRENT_SOURCE_DIR}/common/constants.h)
 
-set(MPIIO_INTERNAL_ADAPTER_SRC ${CMAKE_CURRENT_SOURCE_DIR}/metadata_manager.cc
-        ${CMAKE_CURRENT_SOURCE_DIR}/mapper/balanced_mapper.cc)
-
 # Add library hermes_mpiio
 add_library(hermes_mpiio SHARED ${MPIIO_ADAPTER_PRIVATE_HEADER} ${MPIIO_ADAPTER_PUBLIC_HEADER} ${MPIIO_ADAPTER_SRC})
 add_dependencies(hermes_mpiio hermes)
 target_link_libraries(hermes_mpiio hermes MPI::MPI_CXX)
 
-add_library(hermes_mpiio_internal SHARED ${MPIIO_ADAPTER_PRIVATE_HEADER} ${MPIIO_ADAPTER_PUBLIC_HEADER} ${MPIIO_INTERNAL_ADAPTER_SRC})
-add_dependencies(hermes_mpiio_internal hermes)
-target_link_libraries(hermes_mpiio_internal hermes MPI::MPI_CXX)
-
 #-----------------------------------------------------------------------------
 # Add Target(s) to CMake Install
 #-----------------------------------------------------------------------------
@@ -46,4 +39,4 @@ install(
 #-----------------------------------------------------------------------------
 if(HERMES_ENABLE_COVERAGE)
     set_coverage_flags(hermes_mpiio)
-endif()
\ No newline at end of file
+endif()
diff --git a/adapter/src/hermes/adapter/mpiio/common/constants.h b/adapter/src/hermes/adapter/mpiio/common/constants.h
index cf85363df..a2d71412b 100644
--- a/adapter/src/hermes/adapter/mpiio/common/constants.h
+++ b/adapter/src/hermes/adapter/mpiio/common/constants.h
@@ -35,10 +35,7 @@ using hermes::adapter::mpiio::MapperType;
  * Which mapper to be used by MPIIO adapter.
  */
 const MapperType kMapperType = MapperType::BALANCED;
-/**
- * Define kPageSize for balanced mapping.
- */
-const size_t kPageSize = 1024 * 1024;
+
 /**
  * String delimiter
  */
diff --git a/adapter/src/hermes/adapter/posix/CMakeLists.txt b/adapter/src/hermes/adapter/posix/CMakeLists.txt
index 90aba5959..f64da4c04 100644
--- a/adapter/src/hermes/adapter/posix/CMakeLists.txt
+++ b/adapter/src/hermes/adapter/posix/CMakeLists.txt
@@ -17,18 +17,11 @@ set(POSIX_ADAPTER_PRIVATE_HEADER ${CMAKE_CURRENT_SOURCE_DIR}/metadata_manager.h
         ${CMAKE_CURRENT_SOURCE_DIR}/common/enumerations.h
         ${CMAKE_CURRENT_SOURCE_DIR}/common/constants.h)
 
-set(POSIX_INTERNAL_ADAPTER_SRC ${CMAKE_CURRENT_SOURCE_DIR}/metadata_manager.cc
-        ${CMAKE_CURRENT_SOURCE_DIR}/mapper/balanced_mapper.cc)
-
 # Add library hermes_posix
 add_library(hermes_posix SHARED ${POSIX_ADAPTER_PRIVATE_HEADER} ${POSIX_ADAPTER_PUBLIC_HEADER} ${POSIX_ADAPTER_SRC})
 add_dependencies(hermes_posix hermes)
 target_link_libraries(hermes_posix hermes MPI::MPI_CXX)
 
-add_library(hermes_posix_internal SHARED ${POSIX_ADAPTER_PRIVATE_HEADER} ${POSIX_ADAPTER_PUBLIC_HEADER} ${POSIX_INTERNAL_ADAPTER_SRC})
-add_dependencies(hermes_posix_internal hermes)
-target_link_libraries(hermes_posix_internal hermes MPI::MPI_CXX)
-
 #-----------------------------------------------------------------------------
 # Add Target(s) to CMake Install
 #-----------------------------------------------------------------------------
@@ -46,4 +39,4 @@ install(
 #-----------------------------------------------------------------------------
 if(HERMES_ENABLE_COVERAGE)
     set_coverage_flags(hermes_posix)
-endif()
\ No newline at end of file
+endif()
diff --git a/adapter/src/hermes/adapter/posix/common/constants.h b/adapter/src/hermes/adapter/posix/common/constants.h
index 4f85f76b1..21130b853 100644
--- a/adapter/src/hermes/adapter/posix/common/constants.h
+++ b/adapter/src/hermes/adapter/posix/common/constants.h
@@ -35,10 +35,7 @@ using hermes::adapter::posix::MapperType;
  * Which mapper to be used by POSIX adapter.
  */
 const MapperType kMapperType = MapperType::BALANCED;
-/**
- * Define kPageSize for balanced mapping.
- */
-const size_t kPageSize = 1024 * 1024;
+
 /**
  * String delimiter
  */
diff --git a/adapter/src/hermes/adapter/posix/posix.cc b/adapter/src/hermes/adapter/posix/posix.cc
index 3010e2994..3f1bcaa4d 100644
--- a/adapter/src/hermes/adapter/posix/posix.cc
+++ b/adapter/src/hermes/adapter/posix/posix.cc
@@ -13,7 +13,9 @@
 #include <hermes/adapter/posix.h>
 
 #include <experimental/filesystem>
+
 #include <hermes/adapter/interceptor.cc>
+#include <hermes/adapter/utils.cc>
 #include <hermes/adapter/posix/mapper/balanced_mapper.cc>
 #include <hermes/adapter/posix/metadata_manager.cc>
 
@@ -24,11 +26,14 @@ using hermes::adapter::posix::MetadataManager;
 
 namespace hapi = hermes::api;
 namespace fs = std::experimental::filesystem;
+
+using hermes::u8;
+
 /**
  * Internal Functions
  */
-size_t perform_file_write(std::string &filename, off_t offset, size_t size,
-                          unsigned char *data_ptr) {
+size_t perform_file_write(const std::string &filename, off_t offset,
+                          size_t size, u8 *data_ptr) {
   LOG(INFO) << "Writing to file: " << filename << " offset: " << offset
             << " of size:" << size << "." << std::endl;
   INTERCEPTOR_LIST->hermes_flush_exclusion.insert(filename);
@@ -130,199 +135,152 @@ int open_internal(const std::string &path_str, int flags, int mode) {
   return ret;
 }
 
-size_t write_internal(std::pair<AdapterStat, bool> &existing, const void *ptr,
-                      size_t total_size, int fp) {
-  LOG(INFO) << "Write called for filename: "
-            << existing.first.st_bkid->GetName()
-            << " on offset: " << existing.first.st_ptr
-            << " and size: " << total_size << std::endl;
-  size_t ret;
+void PutWithPosixFallback(AdapterStat &stat, const std::string &blob_name,
+                          const std::string &filename, u8 *data, size_t size,
+                          size_t offset) {
+  hapi::Context ctx;
+  const char *hermes_write_only = getenv(kHermesWriteOnlyVar);
+
+  if (hermes_write_only && hermes_write_only[0] == '1') {
+    // Custom DPE for write-only apps like VPIC
+    ctx.rr_retry = true;
+    ctx.disable_swap = true;
+  }
+
+  hapi::Status status = stat.st_bkid->Put(blob_name, data, size, ctx);
+  if (status.Failed()) {
+    LOG(WARNING) << "Failed to Put Blob " << blob_name << " to Bucket "
+                 << filename << ". Falling back to posix I/O." << std::endl;
+    perform_file_write(filename, offset, size, data);
+  } else {
+    stat.st_blobs.emplace(blob_name);
+  }
+}
+
+size_t write_internal(AdapterStat &stat, const void *ptr, size_t total_size,
+                      int fp) {
+  std::shared_ptr<hapi::Bucket> bkt = stat.st_bkid;
+  std::string filename = bkt->GetName();
+
+  LOG(INFO) << "Write called for filename: " << filename << " on offset: "
+            << stat.st_ptr << " and size: " << total_size << std::endl;
+
+  size_t ret = 0;
   auto mdm = hermes::adapter::Singleton<MetadataManager>::GetInstance();
   auto mapper = MapperFactory().Get(kMapperType);
   auto mapping = mapper->map(
-      FileStruct(mdm->Convert(fp), existing.first.st_ptr, total_size));
+      FileStruct(mdm->Convert(fp), stat.st_ptr, total_size));
   size_t data_offset = 0;
-  auto filename = existing.first.st_bkid->GetName();
-  LOG(INFO) << "Mapping for write has " << mapping.size() << " mapping."
-            << std::endl;
-  for (const auto &item : mapping) {
-    hapi::Context ctx;
-    auto index = std::stol(item.second.blob_name_) - 1;
-    auto blob_exists =
-        existing.first.st_bkid->ContainsBlob(item.second.blob_name_);
-    unsigned char *put_data_ptr = (unsigned char *)ptr + data_offset;
-    size_t put_data_ptr_size = item.first.size_;
-
-    if (!blob_exists || item.second.size_ == kPageSize) {
-      LOG(INFO) << "Create or Overwrite blob " << item.second.blob_name_
-                << " of size:" << item.second.size_ << "." << std::endl;
-      if (item.second.size_ == kPageSize) {
-        auto status = existing.first.st_bkid->Put(
-            item.second.blob_name_, put_data_ptr, put_data_ptr_size, ctx);
-        if (status.Failed()) {
-          perform_file_write(filename, item.first.offset_, put_data_ptr_size,
-                             put_data_ptr);
-        } else {
-          existing.first.st_blobs.emplace(item.second.blob_name_);
-        }
-      } else if (item.second.offset_ == 0) {
-        auto status = existing.first.st_bkid->Put(
-            item.second.blob_name_, put_data_ptr, put_data_ptr_size, ctx);
-        if (status.Failed()) {
-          perform_file_write(filename, index * kPageSize, put_data_ptr_size,
-                             put_data_ptr);
-        } else {
-          existing.first.st_blobs.emplace(item.second.blob_name_);
-        }
+  LOG(INFO) << "Mapping for write has " << mapping.size() << " mappings.\n";
+
+  for (const auto &[finfo, hinfo] : mapping) {
+    auto index = std::stol(hinfo.blob_name_) - 1;
+    size_t offset = index * kPageSize;
+    auto blob_exists = bkt->ContainsBlob(hinfo.blob_name_);
+    u8 *put_data_ptr = (u8 *)ptr + data_offset;
+    size_t put_data_ptr_size = finfo.size_;
+
+    if (!blob_exists || hinfo.size_ == kPageSize) {
+      LOG(INFO) << "Create or Overwrite blob " << hinfo.blob_name_
+                << " of size:" << hinfo.size_ << "." << std::endl;
+      if (hinfo.size_ == kPageSize) {
+        PutWithPosixFallback(stat, hinfo.blob_name_, filename, put_data_ptr,
+                             put_data_ptr_size, finfo.offset_);
+      } else if (hinfo.offset_ == 0) {
+        PutWithPosixFallback(stat, hinfo.blob_name_, filename, put_data_ptr,
+                             put_data_ptr_size, offset);
       } else {
-        hapi::Blob final_data(item.second.offset_ + item.second.size_);
-        if (fs::exists(filename) &&
-            fs::file_size(filename) >= item.second.offset_) {
-          LOG(INFO) << "Blob has a gap in write. read gap from original file."
-                    << std::endl;
-          INTERCEPTOR_LIST->hermes_flush_exclusion.insert(filename);
-          FILE *fh = fopen(filename.c_str(), "r");
-          if (fh != nullptr) {
-            if (fseek(fh, index * kPageSize, SEEK_SET) == 0) {
-              size_t items_read = fread(final_data.data(), item.second.offset_,
-                                        sizeof(char), fh);
-              if (items_read != 1) {
-                // TODO(hari) @errorhandling read failed.
-              }
-              if (fclose(fh) != 0) {
-                // TODO(hari) @errorhandling fclose failed.
-              }
-            } else {
-              // TODO(hari) @errorhandling fseek failed.
-            }
-          } else {
-            // TODO(hari) @errorhandling FILE cannot be opened
-          }
-          INTERCEPTOR_LIST->hermes_flush_exclusion.erase(filename);
-        }
-        memcpy(final_data.data() + item.second.offset_, put_data_ptr,
+        hapi::Blob final_data(hinfo.offset_ + hinfo.size_);
+
+        ReadGap(filename, offset, final_data.data(), hinfo.offset_,
+                hinfo.offset_);
+        memcpy(final_data.data() + hinfo.offset_, put_data_ptr,
                put_data_ptr_size);
-        auto status = existing.first.st_bkid->Put(item.second.blob_name_,
-                                                  final_data, ctx);
-        if (status.Failed()) {
-          perform_file_write(filename, index * kPageSize, final_data.size(),
-                             final_data.data());
-        } else {
-          existing.first.st_blobs.emplace(item.second.blob_name_);
-        }
+        PutWithPosixFallback(stat, hinfo.blob_name_, filename,
+                             final_data.data(), final_data.size(), offset);
       }
-
     } else {
-      LOG(INFO) << "Blob " << item.second.blob_name_
-                << " of size:" << item.second.size_ << " exists." << std::endl;
+      LOG(INFO) << "Blob " << hinfo.blob_name_
+                << " of size:" << hinfo.size_ << " exists." << std::endl;
       hapi::Blob temp(0);
-      auto existing_blob_size =
-          existing.first.st_bkid->Get(item.second.blob_name_, temp, ctx);
-      if (item.second.offset_ == 0) {
+      auto existing_blob_size = bkt->Get(hinfo.blob_name_, temp);
+      if (hinfo.offset_ == 0) {
         LOG(INFO) << "Blob offset is 0" << std::endl;
-        if (item.second.size_ >= existing_blob_size) {
-          LOG(INFO) << "Overwrite blob " << item.second.blob_name_
-                    << " of size:" << item.second.size_ << "." << std::endl;
-          auto status = existing.first.st_bkid->Put(
-              item.second.blob_name_, put_data_ptr, put_data_ptr_size, ctx);
-          if (status.Failed()) {
-            perform_file_write(filename, index * kPageSize, put_data_ptr_size,
-                               put_data_ptr);
-          } else {
-            existing.first.st_blobs.emplace(item.second.blob_name_);
-          }
+        if (hinfo.size_ >= existing_blob_size) {
+          LOG(INFO) << "Overwrite blob " << hinfo.blob_name_
+                    << " of size:" << hinfo.size_ << "." << std::endl;
+          PutWithPosixFallback(stat, hinfo.blob_name_, filename,
+                               put_data_ptr, put_data_ptr_size, offset);
         } else {
-          LOG(INFO) << "Update blob " << item.second.blob_name_
+          LOG(INFO) << "Update blob " << hinfo.blob_name_
                     << " of size:" << existing_blob_size << "." << std::endl;
           hapi::Blob existing_data(existing_blob_size);
-          existing.first.st_bkid->Get(item.second.blob_name_, existing_data,
-                                      ctx);
+          bkt->Get(hinfo.blob_name_, existing_data);
           memcpy(existing_data.data(), put_data_ptr, put_data_ptr_size);
-          auto status = existing.first.st_bkid->Put(item.second.blob_name_,
-                                                    existing_data, ctx);
-          if (status.Failed()) {
-            perform_file_write(filename, index * kPageSize, existing_blob_size,
-                               existing_data.data());
-          } else {
-            existing.first.st_blobs.emplace(item.second.blob_name_);
-          }
+
+          PutWithPosixFallback(stat, hinfo.blob_name_, filename,
+                               existing_data.data(), existing_data.size(),
+                               offset);
         }
       } else {
-        LOG(INFO) << "Blob offset: " << item.second.offset_ << "." << std::endl;
-        auto new_size = item.second.offset_ + item.second.size_;
+        LOG(INFO) << "Blob offset: " << hinfo.offset_ << "." << std::endl;
+        auto new_size = hinfo.offset_ + hinfo.size_;
         hapi::Blob existing_data(existing_blob_size);
-        existing.first.st_bkid->Get(item.second.blob_name_, existing_data, ctx);
-        existing.first.st_bkid->DeleteBlob(item.second.blob_name_, ctx);
+        bkt->Get(hinfo.blob_name_, existing_data);
+        bkt->DeleteBlob(hinfo.blob_name_);
         if (new_size < existing_blob_size) {
           new_size = existing_blob_size;
         }
         hapi::Blob final_data(new_size);
-        auto existing_data_cp_size = existing_data.size() >= item.second.offset_
-                                         ? item.second.offset_
-                                         : existing_data.size();
+        auto existing_data_cp_size = existing_data.size() >= hinfo.offset_
+                                         ? hinfo.offset_ : existing_data.size();
         memcpy(final_data.data(), existing_data.data(), existing_data_cp_size);
 
-        if (existing_blob_size < item.second.offset_ + 1 &&
-            fs::exists(filename) &&
-            fs::file_size(filename) >=
-                item.second.offset_ + item.second.size_) {
-          size_t size_to_read = item.second.offset_ - existing_blob_size;
-          LOG(INFO) << "Blob has a gap in update read gap from original file."
-                    << std::endl;
-          INTERCEPTOR_LIST->hermes_flush_exclusion.insert(filename);
-          FILE *fh = fopen(filename.c_str(), "r");
-          if (fh != nullptr) {
-            if (fseek(fh, index * kPageSize + existing_data_cp_size,
-                      SEEK_SET) == 0) {
-              size_t items_read =
-                  fread(final_data.data() + existing_data_cp_size, size_to_read,
-                        sizeof(char), fh);
-              if (items_read != 1) {
-                // TODO(hari) @errorhandling read failed.
-              }
-              if (fclose(fh) != 0) {
-                // TODO(hari) @errorhandling fclose failed.
-              }
-            } else {
-              // TODO(hari) @errorhandling fseek failed.
-            }
-          } else {
-            // TODO(hari) @errorhandling FILE cannot be opened
-          }
-          INTERCEPTOR_LIST->hermes_flush_exclusion.erase(filename);
+        if (existing_blob_size < hinfo.offset_ + 1) {
+          ReadGap(filename, offset + existing_data_cp_size,
+                  final_data.data() + existing_data_cp_size,
+                  hinfo.offset_ - existing_blob_size,
+                  hinfo.offset_ + hinfo.size_);
         }
-        memcpy(final_data.data() + item.second.offset_, put_data_ptr,
+        memcpy(final_data.data() + hinfo.offset_, put_data_ptr,
                put_data_ptr_size);
-        if (item.second.offset_ + item.second.size_ < existing_blob_size) {
+
+        if (hinfo.offset_ + hinfo.size_ < existing_blob_size) {
           LOG(INFO) << "Retain last portion of blob as Blob is bigger than the "
-                       "update."
-                    << std::endl;
-          auto off_t = item.second.offset_ + item.second.size_;
+                       "update." << std::endl;
+          auto off_t = hinfo.offset_ + hinfo.size_;
           memcpy(final_data.data() + off_t, existing_data.data() + off_t,
                  existing_blob_size - off_t);
         }
-        auto status = existing.first.st_bkid->Put(item.second.blob_name_,
-                                                  final_data, ctx);
-        if (status.Failed()) {
-          perform_file_write(filename, index * kPageSize, new_size,
-                             final_data.data());
-        } else {
-          existing.first.st_blobs.emplace(item.second.blob_name_);
-        }
+
+        PutWithPosixFallback(stat, hinfo.blob_name_, filename,
+                             final_data.data(), final_data.size(), offset);
       }
     }
-    data_offset += item.first.size_;
+    data_offset += finfo.size_;
+
+    // TODO(chogan):
+    // if (PersistEagerly(filename)) {
+    //   hapi::Trait *trait = stat.st_vbkt->GetTrait(hapi::TraitType::PERSIST);
+    //   if (trait) {
+    //     hapi::PersistTrait *persist_trait = (hapi::PersistTrait *)trait;
+    //     persist_trait->file_mapping.offset_map.emplace(hinfo.blob_name_,
+    //                                                    offset);
+    //   }
+
+    //   stat.st_vbkt->Link(hinfo.blob_name_, filename);
+    // }
   }
-  existing.first.st_ptr += data_offset;
-  existing.first.st_size = existing.first.st_size >= existing.first.st_ptr
-                               ? existing.first.st_size
-                               : existing.first.st_ptr;
+  stat.st_ptr += data_offset;
+  stat.st_size = stat.st_size >= stat.st_ptr ? stat.st_size : stat.st_ptr;
+
   struct timespec ts;
   timespec_get(&ts, TIME_UTC);
-  existing.first.st_mtim = ts;
-  existing.first.st_ctim = ts;
-  mdm->Update(fp, existing.first);
+  stat.st_mtim = ts;
+  stat.st_ctim = ts;
+  mdm->Update(fp, stat);
   ret = data_offset;
+
   return ret;
 }
 
@@ -572,7 +530,7 @@ ssize_t HERMES_DECL(write)(int fd, const void *buf, size_t count) {
     auto existing = mdm->Find(fd);
     if (existing.second) {
       LOG(INFO) << "Intercept write." << std::endl;
-      ret = write_internal(existing, buf, count, fd);
+      ret = write_internal(existing.first, buf, count, fd);
     } else {
       MAP_OR_FAIL(write);
       ret = real_write_(fd, buf, count);
@@ -614,7 +572,7 @@ ssize_t HERMES_DECL(pwrite)(int fd, const void *buf, size_t count,
       LOG(INFO) << "Intercept pwrite." << std::endl;
       int status = lseek(fd, offset, SEEK_SET);
       if (status == 0) {
-        ret = write_internal(existing, buf, count, fd);
+        ret = write_internal(existing.first, buf, count, fd);
       }
     } else {
       MAP_OR_FAIL(pwrite);
@@ -657,7 +615,7 @@ ssize_t HERMES_DECL(pwrite64)(int fd, const void *buf, size_t count,
       LOG(INFO) << "Intercept pwrite." << std::endl;
       int status = lseek(fd, offset, SEEK_SET);
       if (status == 0) {
-        ret = write_internal(existing, buf, count, fd);
+        ret = write_internal(existing.first, buf, count, fd);
       }
     } else {
       MAP_OR_FAIL(pwrite);
diff --git a/adapter/src/hermes/adapter/stdio/CMakeLists.txt b/adapter/src/hermes/adapter/stdio/CMakeLists.txt
index 9bd79cbe9..b1ae5151f 100644
--- a/adapter/src/hermes/adapter/stdio/CMakeLists.txt
+++ b/adapter/src/hermes/adapter/stdio/CMakeLists.txt
@@ -17,18 +17,11 @@ set(STDIO_ADAPTER_PRIVATE_HEADER ${CMAKE_CURRENT_SOURCE_DIR}/metadata_manager.h
         ${CMAKE_CURRENT_SOURCE_DIR}/common/enumerations.h
         ${CMAKE_CURRENT_SOURCE_DIR}/common/constants.h)
 
-set(STDIO_INTERNAL_ADAPTER_SRC ${CMAKE_CURRENT_SOURCE_DIR}/metadata_manager.cc
-        ${CMAKE_CURRENT_SOURCE_DIR}/mapper/balanced_mapper.cc)
-
 # Add library hermes_stdio
 add_library(hermes_stdio SHARED ${STDIO_ADAPTER_PRIVATE_HEADER} ${STDIO_ADAPTER_PUBLIC_HEADER} ${STDIO_ADAPTER_SRC})
 add_dependencies(hermes_stdio hermes)
 target_link_libraries(hermes_stdio hermes MPI::MPI_CXX)
 
-add_library(hermes_stdio_internal SHARED ${STDIO_ADAPTER_PRIVATE_HEADER} ${STDIO_ADAPTER_PUBLIC_HEADER} ${STDIO_INTERNAL_ADAPTER_SRC})
-add_dependencies(hermes_stdio_internal hermes)
-target_link_libraries(hermes_stdio_internal hermes MPI::MPI_CXX)
-
 #-----------------------------------------------------------------------------
 # Add Target(s) to CMake Install
 #-----------------------------------------------------------------------------
diff --git a/adapter/src/hermes/adapter/stdio/common/constants.h b/adapter/src/hermes/adapter/stdio/common/constants.h
index ceba40aa5..320236a9a 100644
--- a/adapter/src/hermes/adapter/stdio/common/constants.h
+++ b/adapter/src/hermes/adapter/stdio/common/constants.h
@@ -13,19 +13,8 @@
 #ifndef HERMES_STDIO_COMMON_CONSTANTS_H
 #define HERMES_STDIO_COMMON_CONSTANTS_H
 
-/**
- * Standard header
- */
 #include <cstdlib>
 
-/**
- * Dependent library header
- */
-#include "glog/logging.h"
-
-/**
- * Internal header
- */
 #include <hermes/adapter/stdio/common/enumerations.h>
 
 /**
@@ -38,28 +27,6 @@ using hermes::adapter::stdio::MapperType;
  */
 const MapperType kMapperType = MapperType::BALANCED;
 
-/**
- * Define kPageSize for balanced mapping.
- */
-const size_t kPageSize = []() {
-  const char *kPageSizeVar = "HERMES_PAGE_SIZE";
-  const size_t kDefaultPageSize = 1 * 1024 * 1024;
-
-  size_t result = kDefaultPageSize;
-  char *page_size = getenv(kPageSizeVar);
-
-  if (page_size) {
-    result = (size_t)std::strtoull(page_size, NULL, 0);
-    if (result == 0) {
-      LOG(FATAL) << "Invalid value of " << kPageSizeVar << ": " << page_size;
-    }
-  }
-
-  LOG(INFO) << "Stdio adapter page size: " << result << "\n";
-
-  return result;
-}();
-
 /**
  * String delimiter
  */
diff --git a/adapter/src/hermes/adapter/stdio/stdio.cc b/adapter/src/hermes/adapter/stdio/stdio.cc
index 197b1ec0d..d0fbd192b 100644
--- a/adapter/src/hermes/adapter/stdio/stdio.cc
+++ b/adapter/src/hermes/adapter/stdio/stdio.cc
@@ -16,6 +16,7 @@
 #include <sys/file.h>
 
 #include <hermes/adapter/interceptor.cc>
+#include <hermes/adapter/utils.cc>
 #include <hermes/adapter/stdio/mapper/balanced_mapper.cc>
 #include <hermes/adapter/stdio/metadata_manager.cc>
 
@@ -214,42 +215,11 @@ FILE *reopen_internal(const std::string &path_str, const char *mode,
   return ret;
 }
 
-void ReadGap(const std::string &filename, size_t seek_offset, u8 *read_ptr,
-             size_t read_size, size_t file_bounds) {
-  if (fs::exists(filename) &&
-      fs::file_size(filename) >= file_bounds) {
-    LOG(INFO) << "Blob has a gap in write. Read gap from original file.\n";
-    INTERCEPTOR_LIST->hermes_flush_exclusion.insert(filename);
-    int fd = open(filename.c_str(), O_RDONLY);
-    if (fd) {
-      if (flock(fd, LOCK_SH) == -1) {
-        hermes::FailedLibraryCall("flock");
-      }
-
-      ssize_t bytes_read = pread(fd, read_ptr, read_size, seek_offset);
-      if (bytes_read == -1 || (size_t)bytes_read != read_size) {
-        hermes::FailedLibraryCall("pread");
-      }
-
-      if (flock(fd, LOCK_UN) == -1) {
-        hermes::FailedLibraryCall("flock");
-      }
-
-      if (close(fd) != 0) {
-        hermes::FailedLibraryCall("close");
-      }
-    } else {
-      hermes::FailedLibraryCall("open");
-    }
-    INTERCEPTOR_LIST->hermes_flush_exclusion.erase(filename);
-  }
-}
-
 void PutWithStdioFallback(AdapterStat &stat, const std::string &blob_name,
                           const std::string &filename, u8 *data, size_t size,
                           size_t offset) {
   hapi::Context ctx;
-  const char *hermes_write_only = getenv("HERMES_WRITE_ONLY");
+  const char *hermes_write_only = getenv(kHermesWriteOnlyVar);
 
   if (hermes_write_only && hermes_write_only[0] == '1') {
     // Custom DPE for write-only apps like VPIC
@@ -274,15 +244,16 @@ size_t write_internal(AdapterStat &stat, const void *ptr, size_t total_size,
 
   LOG(INFO) << "Write called for filename: " << filename << " on offset: "
             << stat.st_ptr << " and size: " << total_size << std::endl;
-  size_t ret;
+
+  size_t ret = 0;
   auto mdm = hermes::adapter::Singleton<MetadataManager>::GetInstance();
   auto mapper = MapperFactory().Get(kMapperType);
   auto mapping = mapper->map(
       FileStruct(mdm->Convert(fp), stat.st_ptr, total_size));
   size_t data_offset = 0;
-  LOG(INFO) << "Mapping for write has " << mapping.size() << " mappings."
-            << std::endl;
-  for (const auto& [finfo, hinfo] : mapping) {
+  LOG(INFO) << "Mapping for write has " << mapping.size() << " mappings.\n";
+
+  for (const auto &[finfo, hinfo] : mapping) {
     auto index = std::stol(hinfo.blob_name_) - 1;
     size_t offset = index * kPageSize;
     auto blob_exists = bkt->ContainsBlob(hinfo.blob_name_);
@@ -293,17 +264,16 @@ size_t write_internal(AdapterStat &stat, const void *ptr, size_t total_size,
       LOG(INFO) << "Create or Overwrite blob " << hinfo.blob_name_
                 << " of size:" << hinfo.size_ << "." << std::endl;
       if (hinfo.size_ == kPageSize) {
-        PutWithStdioFallback(stat, hinfo.blob_name_, filename,
-                             put_data_ptr, put_data_ptr_size,
-                             finfo.offset_);
+        PutWithStdioFallback(stat, hinfo.blob_name_, filename, put_data_ptr,
+                             put_data_ptr_size, finfo.offset_);
       } else if (hinfo.offset_ == 0) {
-        PutWithStdioFallback(stat, hinfo.blob_name_, filename,
-                             put_data_ptr, put_data_ptr_size, offset);
+        PutWithStdioFallback(stat, hinfo.blob_name_, filename, put_data_ptr,
+                             put_data_ptr_size, offset);
       } else {
         hapi::Blob final_data(hinfo.offset_ + hinfo.size_);
 
-        ReadGap(filename, index * kPageSize, final_data.data(),
-                hinfo.offset_, hinfo.offset_);
+        ReadGap(filename, offset, final_data.data(), hinfo.offset_,
+                hinfo.offset_);
         memcpy(final_data.data() + hinfo.offset_, put_data_ptr,
                put_data_ptr_size);
         PutWithStdioFallback(stat, hinfo.blob_name_, filename,
@@ -346,8 +316,8 @@ size_t write_internal(AdapterStat &stat, const void *ptr, size_t total_size,
                                          ? hinfo.offset_ : existing_data.size();
         memcpy(final_data.data(), existing_data.data(), existing_data_cp_size);
 
-        if (existing_blob_size < hinfo.offset_) {
-          ReadGap(filename, index * kPageSize + existing_data_cp_size,
+        if (existing_blob_size < hinfo.offset_ + 1) {
+          ReadGap(filename, offset + existing_data_cp_size,
                   final_data.data() + existing_data_cp_size,
                   hinfo.offset_ - existing_blob_size,
                   hinfo.offset_ + hinfo.size_);
@@ -362,6 +332,7 @@ size_t write_internal(AdapterStat &stat, const void *ptr, size_t total_size,
           memcpy(final_data.data() + off_t, existing_data.data() + off_t,
                  existing_blob_size - off_t);
         }
+
         PutWithStdioFallback(stat, hinfo.blob_name_, filename,
                              final_data.data(), final_data.size(), offset);
       }
diff --git a/adapter/src/hermes/adapter/utils.cc b/adapter/src/hermes/adapter/utils.cc
new file mode 100644
index 000000000..fc79da1d3
--- /dev/null
+++ b/adapter/src/hermes/adapter/utils.cc
@@ -0,0 +1,35 @@
+#include <sys/file.h>
+
+using hermes::u8;
+namespace fs = std::experimental::filesystem;
+
+void ReadGap(const std::string &filename, size_t seek_offset, u8 *read_ptr,
+             size_t read_size, size_t file_bounds) {
+  if (fs::exists(filename) &&
+      fs::file_size(filename) >= file_bounds) {
+    LOG(INFO) << "Blob has a gap in write. Read gap from original file.\n";
+    INTERCEPTOR_LIST->hermes_flush_exclusion.insert(filename);
+    int fd = open(filename.c_str(), O_RDONLY);
+    if (fd) {
+      if (flock(fd, LOCK_SH) == -1) {
+        hermes::FailedLibraryCall("flock");
+      }
+
+      ssize_t bytes_read = pread(fd, read_ptr, read_size, seek_offset);
+      if (bytes_read == -1 || (size_t)bytes_read != read_size) {
+        hermes::FailedLibraryCall("pread");
+      }
+
+      if (flock(fd, LOCK_UN) == -1) {
+        hermes::FailedLibraryCall("flock");
+      }
+
+      if (close(fd) != 0) {
+        hermes::FailedLibraryCall("close");
+      }
+    } else {
+      hermes::FailedLibraryCall("open");
+    }
+    INTERCEPTOR_LIST->hermes_flush_exclusion.erase(filename);
+  }
+}
diff --git a/adapter/test/CMakeLists.txt b/adapter/test/CMakeLists.txt
index e84f471d5..b0c4ac60c 100644
--- a/adapter/test/CMakeLists.txt
+++ b/adapter/test/CMakeLists.txt
@@ -18,7 +18,9 @@ add_dependencies(hermes_daemon hermes)
 function(gcc exec args)
     add_test(NAME Test${exec} COMMAND "${CMAKE_BINARY_DIR}/bin/${exec}" ${args})
     set_property(TEST Test${exec}
-            PROPERTY ENVIRONMENT LSAN_OPTIONS=suppressions=${CMAKE_SOURCE_DIR}/test/data/asan.supp)
+      PROPERTY ENVIRONMENT LSAN_OPTIONS=suppressions=${CMAKE_SOURCE_DIR}/test/data/asan.supp)
+    set_property(TEST Test${exec} APPEND
+      PROPERTY ENVIRONMENT HERMES_CONF=${CMAKE_SOURCE_DIR}/adapter/test/data/hermes.conf)
 endfunction()
 
 function(mpi exec mpi_proc args)
diff --git a/adapter/test/hermes_daemon.cc b/adapter/test/hermes_daemon.cc
index 8854ddad9..aa0783c93 100644
--- a/adapter/test/hermes_daemon.cc
+++ b/adapter/test/hermes_daemon.cc
@@ -1,7 +1,7 @@
-#include <mpi.h>
-
 #include <cstdlib>
 
+#include <mpi.h>
+
 #include "hermes.h"
 
 /**
diff --git a/adapter/test/stdio/CMakeLists.txt b/adapter/test/stdio/CMakeLists.txt
index 2990b9ddd..b6deeb8d3 100644
--- a/adapter/test/stdio/CMakeLists.txt
+++ b/adapter/test/stdio/CMakeLists.txt
@@ -30,8 +30,8 @@ endfunction()
 #------------------------------------------------------------------------------
 add_executable(stdio_adapter_mapper_test stdio_adapter_mapper_test.cpp ${ADAPTER_COMMON})
 target_link_libraries(stdio_adapter_mapper_test
-        hermes_stdio_internal Catch2::Catch2 -lstdc++fs -ldl -lc MPI::MPI_CXX)
-add_dependencies(stdio_adapter_mapper_test hermes_stdio_internal)
+        hermes_stdio Catch2::Catch2 -lstdc++fs -ldl -lc MPI::MPI_CXX)
+add_dependencies(stdio_adapter_mapper_test hermes_stdio)
 gcc(stdio_adapter_mapper_test "")
 
 #------------------------------------------------------------------------------
diff --git a/adapter/test/stdio/stdio_adapter_mapper_test.cpp b/adapter/test/stdio/stdio_adapter_mapper_test.cpp
index 4d8f3e5fb..10ec65853 100644
--- a/adapter/test/stdio/stdio_adapter_mapper_test.cpp
+++ b/adapter/test/stdio/stdio_adapter_mapper_test.cpp
@@ -11,6 +11,7 @@
  * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
 
 #include <catch_config.h>
+#include <hermes/adapter/constants.h>
 #include <hermes/adapter/stdio/common/constants.h>
 #include <hermes/adapter/stdio/common/datastructures.h>
 #include <hermes/adapter/stdio/mapper/mapper_factory.h>
@@ -49,11 +50,15 @@ hermes::adapter::stdio::test::Arguments args;
 hermes::adapter::stdio::test::Info info;
 
 int init(int* argc, char*** argv) {
-  (void)argc;
-  (void)argv;
+  MPI_Init(argc, argv);
+
+  return 0;
+}
+int finalize() {
+  MPI_Finalize();
+
   return 0;
 }
-int finalize() { return 0; }
 
 int pretest() {
   fs::path fullpath = args.directory;