diff --git a/packages/xo-vmdk-to-vhd/src/definitions.js b/packages/xo-vmdk-to-vhd/src/definitions.js
index 03f1a4b47..9009f3c8a 100644
--- a/packages/xo-vmdk-to-vhd/src/definitions.js
+++ b/packages/xo-vmdk-to-vhd/src/definitions.js
@@ -79,33 +79,58 @@ export function unpackHeader(buffer) {
   }
 }
 
-export function createStreamOptimizedHeader(capacitySectors, descriptorSizeSectors, grainDirectoryOffsetSectors = -1) {
+export function createStreamOptimizedHeader(
+  capacitySectors,
+  descriptorSizeSectors,
+  grainDirectoryOffsetSectors = -1,
+  rGrainDirectoryOffsetSectors = 0
+) {
   const headerBuffer = Buffer.alloc(SECTOR_SIZE)
   Buffer.from('KDMV', 'ascii').copy(headerBuffer, 0)
   // version
   headerBuffer.writeUInt32LE(3, 4)
-  // newline, compression, markers
-  const flags = 1 | (1 << 16) | (1 << 17)
+  // newline, secondary grain directory , compression, markers
+  const flags = 1 | (1 << 1) | (1 << 16) | (1 << 17)
   headerBuffer.writeUInt32LE(flags, 8)
+
+  // number of sectors of the full disk
   headerBuffer.writeBigUInt64LE(BigInt(capacitySectors), 12)
+
+  // number of sectors in the data of a grain (uncompressed)
   const grainSizeSectors = 128
   headerBuffer.writeBigUInt64LE(BigInt(grainSizeSectors), 20)
+
+  // offset of the descriptor(should be directly after header which is 1 sector long)
   const descriptorOffsetSectors = 1
   headerBuffer.writeBigUInt64LE(BigInt(descriptorOffsetSectors), 28)
+  // size of the descriptor in sectors
   headerBuffer.writeBigUInt64LE(BigInt(descriptorSizeSectors), 36)
   const numGTEsPerGT = 512
+  // number of entries in a grain table
   headerBuffer.writeUInt32LE(numGTEsPerGT, 44)
-  // The rgdOffset should be ignored because bit 1 of the flags field is not set.
+
+  // redundant grain directory offset
+  headerBuffer.writeBigInt64LE(BigInt(rGrainDirectoryOffsetSectors), 48)
+
+  // grain directory offset in sector
   headerBuffer.writeBigInt64LE(BigInt(grainDirectoryOffsetSectors), 56)
   const grainDirectoryEntries = Math.ceil(Math.ceil(capacitySectors / grainSizeSectors) / numGTEsPerGT)
   const grainTableEntries = grainDirectoryEntries * numGTEsPerGT
   const grainDirectorySizeSectors = Math.ceil((grainDirectoryEntries * 4) / SECTOR_SIZE)
   const grainTableSizeSectors = Math.ceil((grainTableEntries * 4) / SECTOR_SIZE)
-  const overheadSectors = 1 + descriptorSizeSectors + grainDirectorySizeSectors + grainTableSizeSectors
+  let overheadSectors = 1 + descriptorSizeSectors
+  // only grow the header if there really is a grain directory
+  if (grainDirectoryOffsetSectors > 0) {
+    overheadSectors += grainDirectorySizeSectors + grainTableSizeSectors
+  }
+
+  // first offset available for data
   headerBuffer.writeBigInt64LE(BigInt(overheadSectors), 64)
+
   // newline mangling detector
   headerBuffer.write('\n \r\n', 73, 4, 'ascii')
-  // use DEFLATE
+
+  // use DEFLATE compression algorithm
   headerBuffer.writeUInt16LE(1, 77)
   return {
     buffer: headerBuffer,
diff --git a/packages/xo-vmdk-to-vhd/src/vmdk-generate.js b/packages/xo-vmdk-to-vhd/src/vmdk-generate.js
index 3bf035bb3..b294527a7 100644
--- a/packages/xo-vmdk-to-vhd/src/vmdk-generate.js
+++ b/packages/xo-vmdk-to-vhd/src/vmdk-generate.js
@@ -155,15 +155,28 @@ ddb.geometry.cylinders = "${geometry.cylinders}"
     yield track(descriptorBuffer)
     yield* emitBlocks(grainSizeBytes, blockGenerator)
     yield track(createEmptyMarker(MARKER_GT))
-    const tableOffset = streamPosition
+    let tableOffset = streamPosition
+    // grain tables
     yield track(tableBuffer)
+    // redundant grain directory
+    // virtual box and esxi seems to prefer having both
+    yield track(createEmptyMarker(MARKER_GD))
+    yield track(createDirectoryBuffer(headerData.grainDirectoryEntries, tableOffset))
+    const rDirectoryOffset = directoryOffset
+
+    // grain tables (again)
+    yield track(createEmptyMarker(MARKER_GT))
+    tableOffset = streamPosition
+    yield track(tableBuffer)
+    // main grain directory (same data)
     yield track(createEmptyMarker(MARKER_GD))
     yield track(createDirectoryBuffer(headerData.grainDirectoryEntries, tableOffset))
     yield track(createEmptyMarker(MARKER_FOOTER))
     const footer = createStreamOptimizedHeader(
       diskCapacitySectors,
       descriptorSizeSectors,
-      directoryOffset / SECTOR_SIZE
+      directoryOffset / SECTOR_SIZE,
+      rDirectoryOffset / SECTOR_SIZE
     )
     yield track(footer.buffer)
     yield track(createEmptyMarker(MARKER_EOS))