diff --git a/modules/lang-painless/src/main/java/org/elasticsearch/painless/action/PainlessExecuteAction.java b/modules/lang-painless/src/main/java/org/elasticsearch/painless/action/PainlessExecuteAction.java
index a29c39bd6c5..e57bb0a6ea3 100644
--- a/modules/lang-painless/src/main/java/org/elasticsearch/painless/action/PainlessExecuteAction.java
+++ b/modules/lang-painless/src/main/java/org/elasticsearch/painless/action/PainlessExecuteAction.java
@@ -29,8 +29,9 @@ import org.apache.lucene.search.Query;
 import org.apache.lucene.search.ScoreMode;
 import org.apache.lucene.search.Scorer;
 import org.apache.lucene.search.Weight;
-import org.apache.lucene.store.RAMDirectory;
 import org.elasticsearch.Version;
+import org.apache.lucene.store.ByteBuffersDirectory;
+import org.apache.lucene.store.Directory;
 import org.elasticsearch.action.ActionRequestValidationException;
 import org.elasticsearch.action.ActionResponse;
 import org.elasticsearch.action.ActionType;
@@ -562,8 +563,8 @@ public class PainlessExecuteAction extends ActionType<PainlessExecuteAction.Resp
 
             Analyzer defaultAnalyzer = indexService.getIndexAnalyzers().getDefaultIndexAnalyzer();
 
-            try (RAMDirectory ramDirectory = new RAMDirectory()) {
-                try (IndexWriter indexWriter = new IndexWriter(ramDirectory, new IndexWriterConfig(defaultAnalyzer))) {
+            try (Directory directory = new ByteBuffersDirectory()) {
+                try (IndexWriter indexWriter = new IndexWriter(directory, new IndexWriterConfig(defaultAnalyzer))) {
                     String index = indexService.index().getName();
                     String type = indexService.mapperService().documentMapper().type();
                     BytesReference document = request.contextSetup.document;
diff --git a/modules/lang-painless/src/test/java/org/elasticsearch/painless/SimilarityScriptTests.java b/modules/lang-painless/src/test/java/org/elasticsearch/painless/SimilarityScriptTests.java
index 1b4c4eb0ff6..8b9560bbd32 100644
--- a/modules/lang-painless/src/test/java/org/elasticsearch/painless/SimilarityScriptTests.java
+++ b/modules/lang-painless/src/test/java/org/elasticsearch/painless/SimilarityScriptTests.java
@@ -34,8 +34,8 @@ import org.apache.lucene.search.IndexSearcher;
 import org.apache.lucene.search.Query;
 import org.apache.lucene.search.TermQuery;
 import org.apache.lucene.search.TopDocs;
+import org.apache.lucene.store.ByteBuffersDirectory;
 import org.apache.lucene.store.Directory;
-import org.apache.lucene.store.RAMDirectory;
 import org.elasticsearch.index.similarity.ScriptedSimilarity;
 import org.elasticsearch.painless.spi.Whitelist;
 import org.elasticsearch.script.ScriptContext;
@@ -62,7 +62,7 @@ public class SimilarityScriptTests extends ScriptTestCase {
         SimilarityScript.Factory factory = scriptEngine.compile(
                 "foobar", "return query.boost * doc.freq / doc.length", SimilarityScript.CONTEXT, Collections.emptyMap());
         ScriptedSimilarity sim = new ScriptedSimilarity("foobar", null, "foobaz", factory::newInstance, true);
-        Directory dir = new RAMDirectory();
+        Directory dir = new ByteBuffersDirectory();
         IndexWriter w = new IndexWriter(dir, newIndexWriterConfig().setSimilarity(sim));
 
         Document doc = new Document();
@@ -101,7 +101,7 @@ public class SimilarityScriptTests extends ScriptTestCase {
         SimilarityScript.Factory factory = scriptEngine.compile(
                 "foobar", "return weight * doc.freq / doc.length", SimilarityScript.CONTEXT, Collections.emptyMap());
         ScriptedSimilarity sim = new ScriptedSimilarity("foobar", weightFactory::newInstance, "foobaz", factory::newInstance, true);
-        Directory dir = new RAMDirectory();
+        Directory dir = new ByteBuffersDirectory();
         IndexWriter w = new IndexWriter(dir, newIndexWriterConfig().setSimilarity(sim));
 
         Document doc = new Document();
diff --git a/modules/percolator/src/main/java/org/elasticsearch/percolator/PercolateQueryBuilder.java b/modules/percolator/src/main/java/org/elasticsearch/percolator/PercolateQueryBuilder.java
index 882ff082d37..adaf5ca6323 100644
--- a/modules/percolator/src/main/java/org/elasticsearch/percolator/PercolateQueryBuilder.java
+++ b/modules/percolator/src/main/java/org/elasticsearch/percolator/PercolateQueryBuilder.java
@@ -36,7 +36,8 @@ import org.apache.lucene.search.ScoreMode;
 import org.apache.lucene.search.Scorer;
 import org.apache.lucene.search.Weight;
 import org.apache.lucene.search.join.BitSetProducer;
-import org.apache.lucene.store.RAMDirectory;
+import org.apache.lucene.store.ByteBuffersDirectory;
+import org.apache.lucene.store.Directory;
 import org.apache.lucene.util.BitDocIdSet;
 import org.apache.lucene.util.BitSet;
 import org.apache.lucene.util.BytesRef;
@@ -674,8 +675,8 @@ public class PercolateQueryBuilder extends AbstractQueryBuilder<PercolateQueryBu
     }
 
     static IndexSearcher createMultiDocumentSearcher(Analyzer analyzer, Collection<ParsedDocument> docs) {
-        RAMDirectory ramDirectory = new RAMDirectory();
-        try (IndexWriter indexWriter = new IndexWriter(ramDirectory, new IndexWriterConfig(analyzer))) {
+        Directory directory = new ByteBuffersDirectory();
+        try (IndexWriter indexWriter = new IndexWriter(directory, new IndexWriterConfig(analyzer))) {
             // Indexing in order here, so that the user provided order matches with the docid sequencing:
             Iterable<ParseContext.Document> iterable = () -> docs.stream()
                 .map(ParsedDocument::docs)
diff --git a/modules/percolator/src/test/java/org/elasticsearch/percolator/CandidateQueryTests.java b/modules/percolator/src/test/java/org/elasticsearch/percolator/CandidateQueryTests.java
index e9bee2164bd..9c65263df49 100644
--- a/modules/percolator/src/test/java/org/elasticsearch/percolator/CandidateQueryTests.java
+++ b/modules/percolator/src/test/java/org/elasticsearch/percolator/CandidateQueryTests.java
@@ -74,8 +74,8 @@ import org.apache.lucene.search.spans.SpanNearQuery;
 import org.apache.lucene.search.spans.SpanNotQuery;
 import org.apache.lucene.search.spans.SpanOrQuery;
 import org.apache.lucene.search.spans.SpanTermQuery;
+import org.apache.lucene.store.ByteBuffersDirectory;
 import org.apache.lucene.store.Directory;
-import org.apache.lucene.store.RAMDirectory;
 import org.apache.lucene.util.BytesRef;
 import org.elasticsearch.Version;
 import org.elasticsearch.cluster.metadata.IndexMetaData;
@@ -842,7 +842,7 @@ public class CandidateQueryTests extends ESSingleNodeTestCase {
 
         Version v = Version.CURRENT;
 
-        try (RAMDirectory directory = new RAMDirectory()) {
+        try (Directory directory = new ByteBuffersDirectory()) {
             try (IndexWriter iw = new IndexWriter(directory, newIndexWriterConfig())) {
                 List<Document> documents = new ArrayList<>();
                 Document document = new Document();
@@ -881,7 +881,7 @@ public class CandidateQueryTests extends ESSingleNodeTestCase {
         }
 
         // This will trigger using the TermsQuery instead of individual term query clauses in the CoveringQuery:
-        try (RAMDirectory directory = new RAMDirectory()) {
+        try (Directory directory = new ByteBuffersDirectory()) {
             try (IndexWriter iw = new IndexWriter(directory, newIndexWriterConfig())) {
                 Document document = new Document();
                 for (int i = 0; i < 1024; i++) {
diff --git a/server/src/test/java/org/elasticsearch/action/termvectors/AbstractTermVectorsTestCase.java b/server/src/test/java/org/elasticsearch/action/termvectors/AbstractTermVectorsTestCase.java
index 0393f5929ce..70bb016b841 100644
--- a/server/src/test/java/org/elasticsearch/action/termvectors/AbstractTermVectorsTestCase.java
+++ b/server/src/test/java/org/elasticsearch/action/termvectors/AbstractTermVectorsTestCase.java
@@ -45,8 +45,8 @@ import org.apache.lucene.search.IndexSearcher;
 import org.apache.lucene.search.ScoreDoc;
 import org.apache.lucene.search.TermQuery;
 import org.apache.lucene.search.TopDocs;
+import org.apache.lucene.store.ByteBuffersDirectory;
 import org.apache.lucene.store.Directory;
-import org.apache.lucene.store.RAMDirectory;
 import org.elasticsearch.action.admin.indices.alias.Alias;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.common.xcontent.XContentBuilder;
@@ -309,7 +309,7 @@ public abstract class AbstractTermVectorsTestCase extends ESIntegTestCase {
         }
         PerFieldAnalyzerWrapper wrapper = new PerFieldAnalyzerWrapper(new StandardAnalyzer(CharArraySet.EMPTY_SET), mapping);
 
-        Directory dir = new RAMDirectory();
+        Directory dir = new ByteBuffersDirectory();
         IndexWriterConfig conf = new IndexWriterConfig(wrapper);
 
         conf.setOpenMode(IndexWriterConfig.OpenMode.CREATE);
diff --git a/server/src/test/java/org/elasticsearch/common/lucene/search/MultiPhrasePrefixQueryTests.java b/server/src/test/java/org/elasticsearch/common/lucene/search/MultiPhrasePrefixQueryTests.java
index f0d4c88e01c..5803ab8f2b9 100644
--- a/server/src/test/java/org/elasticsearch/common/lucene/search/MultiPhrasePrefixQueryTests.java
+++ b/server/src/test/java/org/elasticsearch/common/lucene/search/MultiPhrasePrefixQueryTests.java
@@ -28,7 +28,7 @@ import org.apache.lucene.index.IndexWriter;
 import org.apache.lucene.index.IndexWriterConfig;
 import org.apache.lucene.index.Term;
 import org.apache.lucene.search.IndexSearcher;
-import org.apache.lucene.store.RAMDirectory;
+import org.apache.lucene.store.ByteBuffersDirectory;
 import org.elasticsearch.common.lucene.Lucene;
 import org.elasticsearch.test.ESTestCase;
 
@@ -36,7 +36,7 @@ import static org.hamcrest.Matchers.equalTo;
 
 public class MultiPhrasePrefixQueryTests extends ESTestCase {
     public void testSimple() throws Exception {
-        IndexWriter writer = new IndexWriter(new RAMDirectory(), new IndexWriterConfig(Lucene.STANDARD_ANALYZER));
+        IndexWriter writer = new IndexWriter(new ByteBuffersDirectory(), new IndexWriterConfig(Lucene.STANDARD_ANALYZER));
         Document doc = new Document();
         doc.add(new Field("field", "aaa bbb ccc ddd", TextField.TYPE_NOT_STORED));
         writer.addDocument(doc);
diff --git a/server/src/test/java/org/elasticsearch/common/lucene/search/morelikethis/MoreLikeThisQueryTests.java b/server/src/test/java/org/elasticsearch/common/lucene/search/morelikethis/MoreLikeThisQueryTests.java
index 337c61243ba..09e8525c6e9 100644
--- a/server/src/test/java/org/elasticsearch/common/lucene/search/morelikethis/MoreLikeThisQueryTests.java
+++ b/server/src/test/java/org/elasticsearch/common/lucene/search/morelikethis/MoreLikeThisQueryTests.java
@@ -27,8 +27,8 @@ import org.apache.lucene.index.IndexReader;
 import org.apache.lucene.index.IndexWriter;
 import org.apache.lucene.index.IndexWriterConfig;
 import org.apache.lucene.search.IndexSearcher;
+import org.apache.lucene.store.ByteBuffersDirectory;
 import org.apache.lucene.store.Directory;
-import org.apache.lucene.store.RAMDirectory;
 import org.elasticsearch.common.lucene.Lucene;
 import org.elasticsearch.common.lucene.search.MoreLikeThisQuery;
 import org.elasticsearch.test.ESTestCase;
@@ -38,7 +38,7 @@ import static org.hamcrest.Matchers.equalTo;
 
 public class MoreLikeThisQueryTests extends ESTestCase {
     public void testSimple() throws Exception {
-        Directory dir = new RAMDirectory();
+        Directory dir = new ByteBuffersDirectory();
         IndexWriter indexWriter = new IndexWriter(dir, new IndexWriterConfig(Lucene.STANDARD_ANALYZER));
         indexWriter.commit();
 
diff --git a/server/src/test/java/org/elasticsearch/common/lucene/store/InputStreamIndexInputTests.java b/server/src/test/java/org/elasticsearch/common/lucene/store/InputStreamIndexInputTests.java
index 74de6b77f77..b6a80dbf722 100644
--- a/server/src/test/java/org/elasticsearch/common/lucene/store/InputStreamIndexInputTests.java
+++ b/server/src/test/java/org/elasticsearch/common/lucene/store/InputStreamIndexInputTests.java
@@ -19,10 +19,11 @@
 
 package org.elasticsearch.common.lucene.store;
 
+import org.apache.lucene.store.ByteBuffersDirectory;
+import org.apache.lucene.store.Directory;
 import org.apache.lucene.store.IOContext;
 import org.apache.lucene.store.IndexInput;
 import org.apache.lucene.store.IndexOutput;
-import org.apache.lucene.store.RAMDirectory;
 import org.elasticsearch.test.ESTestCase;
 
 import java.io.IOException;
@@ -32,7 +33,7 @@ import static org.hamcrest.Matchers.lessThan;
 
 public class InputStreamIndexInputTests extends ESTestCase {
     public void testSingleReadSingleByteLimit() throws IOException {
-        RAMDirectory dir = new RAMDirectory();
+        Directory dir = new ByteBuffersDirectory();
         IndexOutput output = dir.createOutput("test", IOContext.DEFAULT);
         for (int i = 0; i < 3; i++) {
             output.writeByte((byte) 1);
@@ -68,7 +69,7 @@ public class InputStreamIndexInputTests extends ESTestCase {
     }
 
     public void testReadMultiSingleByteLimit1() throws IOException {
-        RAMDirectory dir = new RAMDirectory();
+        Directory dir = new ByteBuffersDirectory();
         IndexOutput output = dir.createOutput("test", IOContext.DEFAULT);
         for (int i = 0; i < 3; i++) {
             output.writeByte((byte) 1);
@@ -106,7 +107,7 @@ public class InputStreamIndexInputTests extends ESTestCase {
     }
 
     public void testSingleReadTwoBytesLimit() throws IOException {
-        RAMDirectory dir = new RAMDirectory();
+        Directory dir = new ByteBuffersDirectory();
         IndexOutput output = dir.createOutput("test", IOContext.DEFAULT);
         for (int i = 0; i < 3; i++) {
             output.writeByte((byte) 1);
@@ -147,7 +148,7 @@ public class InputStreamIndexInputTests extends ESTestCase {
     }
 
     public void testReadMultiTwoBytesLimit1() throws IOException {
-        RAMDirectory dir = new RAMDirectory();
+        Directory dir = new ByteBuffersDirectory();
         IndexOutput output = dir.createOutput("test", IOContext.DEFAULT);
         for (int i = 0; i < 3; i++) {
             output.writeByte((byte) 1);
@@ -190,7 +191,7 @@ public class InputStreamIndexInputTests extends ESTestCase {
     }
 
     public void testReadMultiFourBytesLimit() throws IOException {
-        RAMDirectory dir = new RAMDirectory();
+        Directory dir = new ByteBuffersDirectory();
         IndexOutput output = dir.createOutput("test", IOContext.DEFAULT);
         for (int i = 0; i < 3; i++) {
             output.writeByte((byte) 1);
@@ -228,7 +229,7 @@ public class InputStreamIndexInputTests extends ESTestCase {
     }
 
     public void testMarkRest() throws Exception {
-        RAMDirectory dir = new RAMDirectory();
+        Directory dir = new ByteBuffersDirectory();
         IndexOutput output = dir.createOutput("test", IOContext.DEFAULT);
         for (int i = 0; i < 3; i++) {
             output.writeByte((byte) 1);
diff --git a/server/src/test/java/org/elasticsearch/deps/lucene/SimpleLuceneTests.java b/server/src/test/java/org/elasticsearch/deps/lucene/SimpleLuceneTests.java
index 6b117fc7e96..b6f11ff77ea 100644
--- a/server/src/test/java/org/elasticsearch/deps/lucene/SimpleLuceneTests.java
+++ b/server/src/test/java/org/elasticsearch/deps/lucene/SimpleLuceneTests.java
@@ -42,8 +42,8 @@ import org.apache.lucene.search.SortField;
 import org.apache.lucene.search.TermQuery;
 import org.apache.lucene.search.TopDocs;
 import org.apache.lucene.search.TopFieldDocs;
+import org.apache.lucene.store.ByteBuffersDirectory;
 import org.apache.lucene.store.Directory;
-import org.apache.lucene.store.RAMDirectory;
 import org.apache.lucene.util.BytesRef;
 import org.elasticsearch.common.lucene.Lucene;
 import org.elasticsearch.test.ESTestCase;
@@ -55,7 +55,7 @@ import static org.hamcrest.Matchers.equalTo;
 
 public class SimpleLuceneTests extends ESTestCase {
     public void testSortValues() throws Exception {
-        Directory dir = new RAMDirectory();
+        Directory dir = new ByteBuffersDirectory();
         IndexWriter indexWriter = new IndexWriter(dir, new IndexWriterConfig(Lucene.STANDARD_ANALYZER));
         for (int i = 0; i < 10; i++) {
             Document document = new Document();
@@ -74,7 +74,7 @@ public class SimpleLuceneTests extends ESTestCase {
     }
 
     public void testSimpleNumericOps() throws Exception {
-        Directory dir = new RAMDirectory();
+        Directory dir = new ByteBuffersDirectory();
         IndexWriter indexWriter = new IndexWriter(dir, new IndexWriterConfig(Lucene.STANDARD_ANALYZER));
 
         Document document = new Document();
@@ -104,7 +104,7 @@ public class SimpleLuceneTests extends ESTestCase {
      * first (with load and break).
      */
     public void testOrdering() throws Exception {
-        Directory dir = new RAMDirectory();
+        Directory dir = new ByteBuffersDirectory();
         IndexWriter indexWriter = new IndexWriter(dir, new IndexWriterConfig(Lucene.STANDARD_ANALYZER));
 
         Document document = new Document();
@@ -132,7 +132,7 @@ public class SimpleLuceneTests extends ESTestCase {
     }
 
     public void testNRTSearchOnClosedWriter() throws Exception {
-        Directory dir = new RAMDirectory();
+        Directory dir = new ByteBuffersDirectory();
         IndexWriter indexWriter = new IndexWriter(dir, new IndexWriterConfig(Lucene.STANDARD_ANALYZER));
         DirectoryReader reader = DirectoryReader.open(indexWriter);
 
diff --git a/server/src/test/java/org/elasticsearch/deps/lucene/VectorHighlighterTests.java b/server/src/test/java/org/elasticsearch/deps/lucene/VectorHighlighterTests.java
index 7d01b3992fc..eb8cedeba82 100644
--- a/server/src/test/java/org/elasticsearch/deps/lucene/VectorHighlighterTests.java
+++ b/server/src/test/java/org/elasticsearch/deps/lucene/VectorHighlighterTests.java
@@ -35,8 +35,8 @@ import org.apache.lucene.search.TermQuery;
 import org.apache.lucene.search.TopDocs;
 import org.apache.lucene.search.vectorhighlight.CustomFieldQuery;
 import org.apache.lucene.search.vectorhighlight.FastVectorHighlighter;
+import org.apache.lucene.store.ByteBuffersDirectory;
 import org.apache.lucene.store.Directory;
-import org.apache.lucene.store.RAMDirectory;
 import org.elasticsearch.common.lucene.Lucene;
 import org.elasticsearch.test.ESTestCase;
 
@@ -46,7 +46,7 @@ import static org.hamcrest.Matchers.nullValue;
 
 public class VectorHighlighterTests extends ESTestCase {
     public void testVectorHighlighter() throws Exception {
-        Directory dir = new RAMDirectory();
+        Directory dir = new ByteBuffersDirectory();
         IndexWriter indexWriter = new IndexWriter(dir, new IndexWriterConfig(Lucene.STANDARD_ANALYZER));
 
         Document document = new Document();
@@ -72,7 +72,7 @@ public class VectorHighlighterTests extends ESTestCase {
     }
 
     public void testVectorHighlighterPrefixQuery() throws Exception {
-        Directory dir = new RAMDirectory();
+        Directory dir = new ByteBuffersDirectory();
         IndexWriter indexWriter = new IndexWriter(dir, new IndexWriterConfig(Lucene.STANDARD_ANALYZER));
 
         Document document = new Document();
@@ -113,7 +113,7 @@ public class VectorHighlighterTests extends ESTestCase {
     }
 
     public void testVectorHighlighterNoStore() throws Exception {
-        Directory dir = new RAMDirectory();
+        Directory dir = new ByteBuffersDirectory();
         IndexWriter indexWriter = new IndexWriter(dir, new IndexWriterConfig(Lucene.STANDARD_ANALYZER));
 
         Document document = new Document();
@@ -138,7 +138,7 @@ public class VectorHighlighterTests extends ESTestCase {
     }
 
     public void testVectorHighlighterNoTermVector() throws Exception {
-        Directory dir = new RAMDirectory();
+        Directory dir = new ByteBuffersDirectory();
         IndexWriter indexWriter = new IndexWriter(dir, new IndexWriterConfig(Lucene.STANDARD_ANALYZER));
 
         Document document = new Document();
diff --git a/server/src/test/java/org/elasticsearch/index/cache/bitset/BitSetFilterCacheTests.java b/server/src/test/java/org/elasticsearch/index/cache/bitset/BitSetFilterCacheTests.java
index 2c75437ee35..8789cc8935d 100644
--- a/server/src/test/java/org/elasticsearch/index/cache/bitset/BitSetFilterCacheTests.java
+++ b/server/src/test/java/org/elasticsearch/index/cache/bitset/BitSetFilterCacheTests.java
@@ -33,8 +33,8 @@ import org.apache.lucene.index.Term;
 import org.apache.lucene.search.MatchAllDocsQuery;
 import org.apache.lucene.search.TermQuery;
 import org.apache.lucene.search.join.BitSetProducer;
+import org.apache.lucene.store.ByteBuffersDirectory;
 import org.apache.lucene.store.Directory;
-import org.apache.lucene.store.RAMDirectory;
 import org.apache.lucene.util.Accountable;
 import org.apache.lucene.util.BitSet;
 import org.elasticsearch.common.lucene.index.ElasticsearchDirectoryReader;
@@ -68,7 +68,7 @@ public class BitSetFilterCacheTests extends ESTestCase {
 
     public void testInvalidateEntries() throws Exception {
         IndexWriter writer = new IndexWriter(
-                new RAMDirectory(),
+                new ByteBuffersDirectory(),
                 new IndexWriterConfig(new StandardAnalyzer()).setMergePolicy(new LogByteSizeMergePolicy())
         );
         Document document = new Document();
@@ -128,7 +128,7 @@ public class BitSetFilterCacheTests extends ESTestCase {
 
     public void testListener() throws IOException {
         IndexWriter writer = new IndexWriter(
-                new RAMDirectory(),
+                new ByteBuffersDirectory(),
                 new IndexWriterConfig(new StandardAnalyzer()).setMergePolicy(new LogByteSizeMergePolicy())
         );
         Document document = new Document();
diff --git a/server/src/test/java/org/elasticsearch/index/fielddata/AbstractFieldDataTestCase.java b/server/src/test/java/org/elasticsearch/index/fielddata/AbstractFieldDataTestCase.java
index 3b4bf428adf..d20bf83d7d0 100644
--- a/server/src/test/java/org/elasticsearch/index/fielddata/AbstractFieldDataTestCase.java
+++ b/server/src/test/java/org/elasticsearch/index/fielddata/AbstractFieldDataTestCase.java
@@ -30,7 +30,7 @@ import org.apache.lucene.index.LeafReaderContext;
 import org.apache.lucene.index.LogByteSizeMergePolicy;
 import org.apache.lucene.search.IndexSearcher;
 import org.apache.lucene.search.Query;
-import org.apache.lucene.store.RAMDirectory;
+import org.apache.lucene.store.ByteBuffersDirectory;
 import org.elasticsearch.common.lucene.index.ElasticsearchDirectoryReader;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.index.IndexService;
@@ -136,7 +136,7 @@ public abstract class AbstractFieldDataTestCase extends ESSingleNodeTestCase {
         indicesFieldDataCache = getInstanceFromNode(IndicesService.class).getIndicesFieldDataCache();
         // LogByteSizeMP to preserve doc ID order
         writer = new IndexWriter(
-            new RAMDirectory(), new IndexWriterConfig(new StandardAnalyzer()).setMergePolicy(new LogByteSizeMergePolicy())
+            new ByteBuffersDirectory(), new IndexWriterConfig(new StandardAnalyzer()).setMergePolicy(new LogByteSizeMergePolicy())
         );
         shardContext = indexService.newQueryShardContext(0, null, () -> 0, null);
     }
diff --git a/server/src/test/java/org/elasticsearch/index/fielddata/IndexFieldDataServiceTests.java b/server/src/test/java/org/elasticsearch/index/fielddata/IndexFieldDataServiceTests.java
index bfa7cf9a9e1..8cece535a68 100644
--- a/server/src/test/java/org/elasticsearch/index/fielddata/IndexFieldDataServiceTests.java
+++ b/server/src/test/java/org/elasticsearch/index/fielddata/IndexFieldDataServiceTests.java
@@ -28,7 +28,7 @@ import org.apache.lucene.index.IndexReader;
 import org.apache.lucene.index.IndexWriter;
 import org.apache.lucene.index.IndexWriterConfig;
 import org.apache.lucene.index.LeafReaderContext;
-import org.apache.lucene.store.RAMDirectory;
+import org.apache.lucene.store.ByteBuffersDirectory;
 import org.apache.lucene.util.Accountable;
 import org.elasticsearch.common.lucene.index.ElasticsearchDirectoryReader;
 import org.elasticsearch.common.settings.Settings;
@@ -110,7 +110,7 @@ public class IndexFieldDataServiceTests extends ESSingleNodeTestCase {
         final BuilderContext ctx = new BuilderContext(indexService.getIndexSettings().getSettings(), new ContentPath(1));
         final MappedFieldType mapper1 = new TextFieldMapper.Builder("field_1").fielddata(true).build(ctx).fieldType();
         final MappedFieldType mapper2 = new TextFieldMapper.Builder("field_2").fielddata(true).build(ctx).fieldType();
-        final IndexWriter writer = new IndexWriter(new RAMDirectory(), new IndexWriterConfig(new KeywordAnalyzer()));
+        final IndexWriter writer = new IndexWriter(new ByteBuffersDirectory(), new IndexWriterConfig(new KeywordAnalyzer()));
         Document doc = new Document();
         doc.add(new StringField("field_1", "thisisastring", Store.NO));
         doc.add(new StringField("field_2", "thisisanotherstring", Store.NO));
@@ -169,7 +169,7 @@ public class IndexFieldDataServiceTests extends ESSingleNodeTestCase {
 
         final BuilderContext ctx = new BuilderContext(indexService.getIndexSettings().getSettings(), new ContentPath(1));
         final MappedFieldType mapper1 = new TextFieldMapper.Builder("s").fielddata(true).build(ctx).fieldType();
-        final IndexWriter writer = new IndexWriter(new RAMDirectory(), new IndexWriterConfig(new KeywordAnalyzer()));
+        final IndexWriter writer = new IndexWriter(new ByteBuffersDirectory(), new IndexWriterConfig(new KeywordAnalyzer()));
         Document doc = new Document();
         doc.add(new StringField("s", "thisisastring", Store.NO));
         writer.addDocument(doc);
diff --git a/server/src/test/java/org/elasticsearch/index/mapper/BooleanFieldMapperTests.java b/server/src/test/java/org/elasticsearch/index/mapper/BooleanFieldMapperTests.java
index 4b4ef72ccd9..74543980d93 100644
--- a/server/src/test/java/org/elasticsearch/index/mapper/BooleanFieldMapperTests.java
+++ b/server/src/test/java/org/elasticsearch/index/mapper/BooleanFieldMapperTests.java
@@ -27,8 +27,8 @@ import org.apache.lucene.index.IndexWriterConfig;
 import org.apache.lucene.index.IndexableField;
 import org.apache.lucene.index.LeafReader;
 import org.apache.lucene.index.SortedNumericDocValues;
+import org.apache.lucene.store.ByteBuffersDirectory;
 import org.apache.lucene.store.Directory;
-import org.apache.lucene.store.RAMDirectory;
 import org.apache.lucene.util.BytesRef;
 import org.elasticsearch.common.Strings;
 import org.elasticsearch.common.bytes.BytesReference;
@@ -80,7 +80,7 @@ public class BooleanFieldMapperTests extends ESSingleNodeTestCase {
                         .endObject()),
                 XContentType.JSON));
 
-        try (Directory dir = new RAMDirectory();
+        try (Directory dir = new ByteBuffersDirectory();
              IndexWriter w = new IndexWriter(dir, new IndexWriterConfig(new MockAnalyzer(random())))) {
             w.addDocuments(doc.docs());
             try (DirectoryReader reader = DirectoryReader.open(w)) {
diff --git a/server/src/test/java/org/elasticsearch/index/mapper/StoredNumericValuesTests.java b/server/src/test/java/org/elasticsearch/index/mapper/StoredNumericValuesTests.java
index 1b279f4d268..1f9a455ff53 100644
--- a/server/src/test/java/org/elasticsearch/index/mapper/StoredNumericValuesTests.java
+++ b/server/src/test/java/org/elasticsearch/index/mapper/StoredNumericValuesTests.java
@@ -23,7 +23,7 @@ import org.apache.lucene.index.DirectoryReader;
 import org.apache.lucene.index.IndexWriter;
 import org.apache.lucene.index.IndexWriterConfig;
 import org.apache.lucene.search.IndexSearcher;
-import org.apache.lucene.store.RAMDirectory;
+import org.apache.lucene.store.ByteBuffersDirectory;
 import org.elasticsearch.common.Strings;
 import org.elasticsearch.common.bytes.BytesReference;
 import org.elasticsearch.common.compress.CompressedXContent;
@@ -41,7 +41,7 @@ import static org.hamcrest.Matchers.equalTo;
 
 public class StoredNumericValuesTests extends ESSingleNodeTestCase {
     public void testBytesAndNumericRepresentation() throws Exception {
-        IndexWriter writer = new IndexWriter(new RAMDirectory(), new IndexWriterConfig(Lucene.STANDARD_ANALYZER));
+        IndexWriter writer = new IndexWriter(new ByteBuffersDirectory(), new IndexWriterConfig(Lucene.STANDARD_ANALYZER));
 
         String mapping = Strings
                 .toString(XContentFactory.jsonBuilder()
diff --git a/server/src/test/java/org/elasticsearch/index/similarity/ScriptedSimilarityTests.java b/server/src/test/java/org/elasticsearch/index/similarity/ScriptedSimilarityTests.java
index 22089bc40e4..755086539fe 100644
--- a/server/src/test/java/org/elasticsearch/index/similarity/ScriptedSimilarityTests.java
+++ b/server/src/test/java/org/elasticsearch/index/similarity/ScriptedSimilarityTests.java
@@ -37,8 +37,8 @@ import org.apache.lucene.search.Query;
 import org.apache.lucene.search.TermQuery;
 import org.apache.lucene.search.TopDocs;
 import org.apache.lucene.search.similarities.BM25Similarity;
+import org.apache.lucene.store.ByteBuffersDirectory;
 import org.apache.lucene.store.Directory;
-import org.apache.lucene.store.RAMDirectory;
 import org.apache.lucene.util.TestUtil;
 import org.apache.lucene.util.Version;
 import org.elasticsearch.script.SimilarityScript;
@@ -117,7 +117,7 @@ public class ScriptedSimilarityTests extends ESTestCase {
             };
         };
         ScriptedSimilarity sim = new ScriptedSimilarity("foobar", null, "foobaz", scriptFactory, true);
-        Directory dir = new RAMDirectory();
+        Directory dir = new ByteBuffersDirectory();
         IndexWriter w = new IndexWriter(dir, newIndexWriterConfig().setSimilarity(sim));
 
         Document doc = new Document();
@@ -211,7 +211,7 @@ public class ScriptedSimilarityTests extends ESTestCase {
             };
         };
         ScriptedSimilarity sim = new ScriptedSimilarity("foobar", weightScriptFactory, "foobaz", scriptFactory, true);
-        Directory dir = new RAMDirectory();
+        Directory dir = new ByteBuffersDirectory();
         IndexWriter w = new IndexWriter(dir, newIndexWriterConfig().setSimilarity(sim));
 
         Document doc = new Document();
diff --git a/server/src/test/java/org/elasticsearch/index/store/StoreTests.java b/server/src/test/java/org/elasticsearch/index/store/StoreTests.java
index 0dbb6aefa17..59feabb699d 100644
--- a/server/src/test/java/org/elasticsearch/index/store/StoreTests.java
+++ b/server/src/test/java/org/elasticsearch/index/store/StoreTests.java
@@ -40,6 +40,7 @@ import org.apache.lucene.index.SegmentInfos;
 import org.apache.lucene.index.SnapshotDeletionPolicy;
 import org.apache.lucene.index.Term;
 import org.apache.lucene.store.BaseDirectoryWrapper;
+import org.apache.lucene.store.ByteBuffersDirectory;
 import org.apache.lucene.store.ChecksumIndexInput;
 import org.apache.lucene.store.Directory;
 import org.apache.lucene.store.FilterDirectory;
@@ -47,7 +48,6 @@ import org.apache.lucene.store.IOContext;
 import org.apache.lucene.store.IndexInput;
 import org.apache.lucene.store.IndexOutput;
 import org.apache.lucene.store.NIOFSDirectory;
-import org.apache.lucene.store.RAMDirectory;
 import org.apache.lucene.util.BytesRef;
 import org.apache.lucene.util.TestUtil;
 import org.apache.lucene.util.Version;
@@ -955,7 +955,7 @@ public class StoreTests extends ESTestCase {
 
     public void testDeserializeCorruptionException() throws IOException {
         final ShardId shardId = new ShardId("index", "_na_", 1);
-        final Directory dir = new RAMDirectory(); // I use ram dir to prevent that virusscanner being a PITA
+        final Directory dir = new ByteBuffersDirectory(); // I use ram dir to prevent that virusscanner being a PITA
         Store store = new Store(shardId, INDEX_SETTINGS, dir, new DummyShardLock(shardId));
         CorruptIndexException ex = new CorruptIndexException("foo", "bar");
         store.markStoreCorrupted(ex);
@@ -984,7 +984,7 @@ public class StoreTests extends ESTestCase {
 
     public void testCorruptionMarkerVersionCheck() throws IOException {
         final ShardId shardId = new ShardId("index", "_na_", 1);
-        final Directory dir = new RAMDirectory(); // I use ram dir to prevent that virusscanner being a PITA
+        final Directory dir = new ByteBuffersDirectory(); // I use ram dir to prevent that virusscanner being a PITA
 
         try (Store store = new Store(shardId, INDEX_SETTINGS, dir, new DummyShardLock(shardId))) {
             final String corruptionMarkerName = Store.CORRUPTED_MARKER_NAME_PREFIX + UUIDs.randomBase64UUID();
diff --git a/server/src/test/java/org/elasticsearch/search/collapse/CollapseBuilderTests.java b/server/src/test/java/org/elasticsearch/search/collapse/CollapseBuilderTests.java
index 7f192dfea61..c69deac7643 100644
--- a/server/src/test/java/org/elasticsearch/search/collapse/CollapseBuilderTests.java
+++ b/server/src/test/java/org/elasticsearch/search/collapse/CollapseBuilderTests.java
@@ -24,8 +24,8 @@ import org.apache.lucene.index.IndexOptions;
 import org.apache.lucene.index.IndexReader;
 import org.apache.lucene.index.IndexWriter;
 import org.apache.lucene.search.Query;
+import org.apache.lucene.store.ByteBuffersDirectory;
 import org.apache.lucene.store.Directory;
-import org.apache.lucene.store.RAMDirectory;
 import org.elasticsearch.common.io.stream.NamedWriteableRegistry;
 import org.elasticsearch.common.io.stream.Writeable;
 import org.elasticsearch.common.settings.Settings;
@@ -137,7 +137,7 @@ public class CollapseBuilderTests extends AbstractSerializingTestCase<CollapseBu
     }
 
     public void testBuild() throws IOException {
-        Directory dir = new RAMDirectory();
+        Directory dir = new ByteBuffersDirectory();
         try (IndexWriter writer = new IndexWriter(dir, newIndexWriterConfig(new MockAnalyzer(random())))) {
             writer.commit();
         }
diff --git a/server/src/test/java/org/elasticsearch/search/slice/SliceBuilderTests.java b/server/src/test/java/org/elasticsearch/search/slice/SliceBuilderTests.java
index 767722bc690..14cc0efb904 100644
--- a/server/src/test/java/org/elasticsearch/search/slice/SliceBuilderTests.java
+++ b/server/src/test/java/org/elasticsearch/search/slice/SliceBuilderTests.java
@@ -27,8 +27,8 @@ import org.apache.lucene.index.IndexWriter;
 import org.apache.lucene.search.MatchAllDocsQuery;
 import org.apache.lucene.search.MatchNoDocsQuery;
 import org.apache.lucene.search.Query;
+import org.apache.lucene.store.ByteBuffersDirectory;
 import org.apache.lucene.store.Directory;
-import org.apache.lucene.store.RAMDirectory;
 import org.elasticsearch.Version;
 import org.elasticsearch.action.OriginalIndices;
 import org.elasticsearch.action.search.SearchRequest;
@@ -204,7 +204,7 @@ public class SliceBuilderTests extends ESTestCase {
     }
 
     public void testToFilterSimple() throws IOException {
-        Directory dir = new RAMDirectory();
+        Directory dir = new ByteBuffersDirectory();
         try (IndexWriter writer = new IndexWriter(dir, newIndexWriterConfig(new MockAnalyzer(random())))) {
             writer.commit();
         }
@@ -224,7 +224,7 @@ public class SliceBuilderTests extends ESTestCase {
     }
 
     public void testToFilterRandom() throws IOException {
-        Directory dir = new RAMDirectory();
+        Directory dir = new ByteBuffersDirectory();
         try (IndexWriter writer = new IndexWriter(dir, newIndexWriterConfig(new MockAnalyzer(random())))) {
             writer.commit();
         }
@@ -307,7 +307,7 @@ public class SliceBuilderTests extends ESTestCase {
     }
 
     public void testInvalidField() throws IOException {
-        Directory dir = new RAMDirectory();
+        Directory dir = new ByteBuffersDirectory();
         try (IndexWriter writer = new IndexWriter(dir, newIndexWriterConfig(new MockAnalyzer(random())))) {
             writer.commit();
         }
@@ -321,7 +321,7 @@ public class SliceBuilderTests extends ESTestCase {
     }
 
     public void testToFilterDeprecationMessage() throws IOException {
-        Directory dir = new RAMDirectory();
+        Directory dir = new ByteBuffersDirectory();
         try (IndexWriter writer = new IndexWriter(dir, newIndexWriterConfig(new MockAnalyzer(random())))) {
             writer.commit();
         }
@@ -351,7 +351,7 @@ public class SliceBuilderTests extends ESTestCase {
     }
 
     public void testToFilterWithRouting() throws IOException {
-        Directory dir = new RAMDirectory();
+        Directory dir = new ByteBuffersDirectory();
         try (IndexWriter writer = new IndexWriter(dir, newIndexWriterConfig(new MockAnalyzer(random())))) {
             writer.commit();
         }
diff --git a/server/src/test/java/org/elasticsearch/search/suggest/phrase/NoisyChannelSpellCheckerTests.java b/server/src/test/java/org/elasticsearch/search/suggest/phrase/NoisyChannelSpellCheckerTests.java
index 94c5bf329eb..f7a0827affa 100644
--- a/server/src/test/java/org/elasticsearch/search/suggest/phrase/NoisyChannelSpellCheckerTests.java
+++ b/server/src/test/java/org/elasticsearch/search/suggest/phrase/NoisyChannelSpellCheckerTests.java
@@ -41,8 +41,8 @@ import org.apache.lucene.index.IndexWriterConfig;
 import org.apache.lucene.index.MultiTerms;
 import org.apache.lucene.search.spell.DirectSpellChecker;
 import org.apache.lucene.search.spell.SuggestMode;
+import org.apache.lucene.store.ByteBuffersDirectory;
 import org.apache.lucene.store.Directory;
-import org.apache.lucene.store.RAMDirectory;
 import org.apache.lucene.util.BytesRef;
 import org.apache.lucene.util.CharsRefBuilder;
 import org.elasticsearch.search.suggest.phrase.NoisyChannelSpellChecker.Result;
@@ -65,7 +65,7 @@ public class NoisyChannelSpellCheckerTests extends ESTestCase {
     private final BytesRef postTag = new BytesRef("</em>");
 
     public void testNgram() throws IOException {
-        RAMDirectory dir = new RAMDirectory();
+        Directory dir = new ByteBuffersDirectory();
         Map<String, Analyzer> mapping = new HashMap<>();
         mapping.put("body_ngram", new Analyzer() {
 
@@ -226,7 +226,7 @@ public class NoisyChannelSpellCheckerTests extends ESTestCase {
     }
 
     public void testMultiGenerator() throws IOException {
-        RAMDirectory dir = new RAMDirectory();
+        Directory dir = new ByteBuffersDirectory();
         Map<String, Analyzer> mapping = new HashMap<>();
         mapping.put("body_ngram", new Analyzer() {
 
@@ -343,7 +343,7 @@ public class NoisyChannelSpellCheckerTests extends ESTestCase {
     }
 
     public void testTrigram() throws IOException {
-        RAMDirectory dir = new RAMDirectory();
+        Directory dir = new ByteBuffersDirectory();
         Map<String, Analyzer> mapping = new HashMap<>();
         mapping.put("body_ngram", new Analyzer() {
 
diff --git a/server/src/test/java/org/elasticsearch/search/suggest/phrase/SmoothingModelTestCase.java b/server/src/test/java/org/elasticsearch/search/suggest/phrase/SmoothingModelTestCase.java
index a65c75817a8..39220c5eaa8 100644
--- a/server/src/test/java/org/elasticsearch/search/suggest/phrase/SmoothingModelTestCase.java
+++ b/server/src/test/java/org/elasticsearch/search/suggest/phrase/SmoothingModelTestCase.java
@@ -29,7 +29,7 @@ import org.apache.lucene.index.DirectoryReader;
 import org.apache.lucene.index.IndexWriter;
 import org.apache.lucene.index.IndexWriterConfig;
 import org.apache.lucene.index.MultiTerms;
-import org.apache.lucene.store.RAMDirectory;
+import org.apache.lucene.store.ByteBuffersDirectory;
 import org.elasticsearch.common.io.stream.NamedWriteableRegistry;
 import org.elasticsearch.common.lucene.BytesRefs;
 import org.elasticsearch.common.xcontent.ToXContent;
@@ -112,7 +112,7 @@ public abstract class SmoothingModelTestCase extends ESTestCase {
         Map<String, Analyzer> mapping = new HashMap<>();
         mapping.put("field", new WhitespaceAnalyzer());
         PerFieldAnalyzerWrapper wrapper = new PerFieldAnalyzerWrapper(new WhitespaceAnalyzer(), mapping);
-        IndexWriter writer = new IndexWriter(new RAMDirectory(), new IndexWriterConfig(wrapper));
+        IndexWriter writer = new IndexWriter(new ByteBuffersDirectory(), new IndexWriterConfig(wrapper));
         Document doc = new Document();
         doc.add(new Field("field", "someText", TextField.TYPE_NOT_STORED));
         writer.addDocument(doc);