SNAPSHOT: Speed up HDFS Repository Writes (#37069)

* There is no point in hsyncing after every individual write since there is only value in completely written blobs for restores, this is ensures by the `SYNC` flag already and there is no need for separately invoking `hsync` after individual writes

plugins/repository-hdfs/src/main/java/org/elasticsearch/repositories/hdfs/HdfsBlobContainer.java

@@ -97,19 +97,13 @@ final class HdfsBlobContainer extends AbstractBlobContainer {
         store.execute((Operation<Void>) fileContext -> {
             Path blob = new Path(path, blobName);
             // we pass CREATE, which means it fails if a blob already exists.
-            EnumSet<CreateFlag> flags = failIfAlreadyExists ? EnumSet.of(CreateFlag.CREATE, CreateFlag.SYNC_BLOCK) :
-                EnumSet.of(CreateFlag.CREATE, CreateFlag.OVERWRITE, CreateFlag.SYNC_BLOCK);
-            CreateOpts[] opts = {CreateOpts.bufferSize(bufferSize)};
-            try (FSDataOutputStream stream = fileContext.create(blob, flags, opts)) {
+            EnumSet<CreateFlag> flags = failIfAlreadyExists ? EnumSet.of(CreateFlag.CREATE, CreateFlag.SYNC_BLOCK)
+                : EnumSet.of(CreateFlag.CREATE, CreateFlag.OVERWRITE, CreateFlag.SYNC_BLOCK);
+            try (FSDataOutputStream stream = fileContext.create(blob, flags, CreateOpts.bufferSize(bufferSize))) {
                 int bytesRead;
                 byte[] buffer = new byte[bufferSize];
                 while ((bytesRead = inputStream.read(buffer)) != -1) {
                     stream.write(buffer, 0, bytesRead);
-                    //  For safety we also hsync each write as well, because of its docs:
-                    //  SYNC_BLOCK - to force closed blocks to the disk device
-                    // "In addition Syncable.hsync() should be called after each write,
-                    //  if true synchronous behavior is required"
-                    stream.hsync();
                 }
             } catch (org.apache.hadoop.fs.FileAlreadyExistsException faee) {
                 throw new FileAlreadyExistsException(blob.toString(), null, faee.getMessage());