diff --git a/ftk/src/ftkfsys.cpp b/ftk/src/ftkfsys.cpp
index 4c53998..bedf9d0 100644
--- a/ftk/src/ftkfsys.cpp
+++ b/ftk/src/ftkfsys.cpp
@@ -2754,6 +2754,7 @@ void F_FileHdl::initCommonData( void)
 	m_bOpenedExclusive = FALSE;
 	m_bOpenedInAsyncMode = FALSE;
 	m_bDoDirectIO = FALSE;
+	m_numAsyncPending = 0;
 }
 
 /*****************************************************************************
@@ -2761,6 +2762,8 @@ Desc:
 ******************************************************************************/
 void F_FileHdl::freeCommonData( void)
 {
+	f_assert( !m_numAsyncPending);
+	
 	if( m_pucAlignedBuff)
 	{
 		f_freeAlignedBuffer( (void **)&m_pucAlignedBuff);
@@ -3033,6 +3036,8 @@ RCODE F_FileAsyncClient::prepareForAsync(
 		m_pIOBuffer->setPending();
 	}
 	
+	f_atomicInc( &m_pFileHdl->m_numAsyncPending);
+	
 Exit:
 
 	return( rc);
@@ -3141,6 +3146,8 @@ void FLMAPI F_FileAsyncClient::notifyComplete(
 	
 	if( m_pFileHdl)
 	{
+		f_assert( m_pFileHdl->m_numAsyncPending);
+		f_atomicDec( &m_pFileHdl->m_numAsyncPending);
 		m_pFileHdl->Release();
 		m_pFileHdl = NULL;
 	}
@@ -3268,6 +3275,10 @@ RCODE F_FileHdl::directRead(
 	{
 		ui64ReadOffset = m_ui64CurrentPos;
 	}
+	else
+	{
+		m_ui64CurrentPos = ui64ReadOffset;
+	}
 
 	// This loop does multiple reads (if necessary) to get all of the
 	// data.  It uses aligned buffers and reads at sector offsets.
@@ -3423,6 +3434,10 @@ RCODE F_FileHdl::directWrite(
 	{
 		ui64WriteOffset = m_ui64CurrentPos;
 	}
+	else
+	{
+		m_ui64CurrentPos = ui64WriteOffset;
+	}
 
 	if( pIOBuffer)
 	{
diff --git a/ftk/src/ftknlm.cpp b/ftk/src/ftknlm.cpp
index d46e8c2..591b442 100644
--- a/ftk/src/ftknlm.cpp
+++ b/ftk/src/ftknlm.cpp
@@ -3014,6 +3014,10 @@ RCODE F_FileHdl::lowLevelRead(
 	{
 		ui64ReadOffset = m_ui64CurrentPos;
 	}
+	else
+	{
+		m_ui64CurrentPos = ui64ReadOffset;
+	}
 	
 	if( !pvBuffer)
 	{
@@ -3335,6 +3339,10 @@ RCODE F_FileHdl::lowLevelWrite(
 	{
 		ui64WriteOffset = m_ui64CurrentPos;
 	}
+	else
+	{
+		m_ui64CurrentPos = ui64WriteOffset;
+	}
 
 	if( !pvBuffer)
 	{
diff --git a/ftk/src/ftksys.h b/ftk/src/ftksys.h
index 4a02fd1..3cd21fe 100644
--- a/ftk/src/ftksys.h
+++ b/ftk/src/ftksys.h
@@ -768,6 +768,7 @@
 		FLMBOOL						m_bOpenedExclusive;
 		FLMBOOL						m_bDoDirectIO;
 		FLMBOOL						m_bOpenedInAsyncMode;
+		FLMATOMIC					m_numAsyncPending;
 		
 	#if defined( FLM_WIN)
 		HANDLE						m_hFile;
diff --git a/ftk/src/ftkunix.cpp b/ftk/src/ftkunix.cpp
index 8591a30..28b1633 100644
--- a/ftk/src/ftkunix.cpp
+++ b/ftk/src/ftkunix.cpp
@@ -480,6 +480,10 @@ RCODE F_FileHdl::lowLevelRead(
 	{
 		ui64ReadOffset = m_ui64CurrentPos;
 	}
+	else
+	{
+		m_ui64CurrentPos = ui64ReadOffset;
+	}
 	
 	if( !pvBuffer)
 	{
@@ -646,6 +650,7 @@ RCODE F_FileHdl::lowLevelWrite(
 	FLMUINT					uiBytesWritten = 0;
 	F_FileAsyncClient *	pAsyncClient = NULL;
 	FLMBOOL					bWaitForWrite = FALSE;
+	FLMBYTE *				pucExtendBuffer = NULL;
 	
 	if( pIOBuffer && pvBuffer && pvBuffer != pIOBuffer->getBufferPtr())
 	{
@@ -657,8 +662,12 @@ RCODE F_FileHdl::lowLevelWrite(
 	{
 		ui64WriteOffset = m_ui64CurrentPos;
 	}
+	else
+	{
+		m_ui64CurrentPos = ui64WriteOffset;
+	}
 
-	if( m_bDoDirectIO)
+	if( m_bDoDirectIO && !m_numAsyncPending)
 	{
 		FLMUINT64			ui64CurrFileSize;
 		FLMUINT				uiTotalBytesToExtend;
@@ -698,19 +707,25 @@ RCODE F_FileHdl::lowLevelWrite(
 
 			if( uiTotalBytesToExtend)
 			{
-				FLMUINT		uiCurrBytesToExtend;
 				FLMINT		iBytesWritten;
+				FLMUINT		uiCurrBytesToExtend;
+				FLMUINT		uiExtendBufferSize;
 				
-				f_memset( m_pucAlignedBuff, 0, m_uiAlignedBuffSize);
+				uiExtendBufferSize = f_min( uiTotalBytesToExtend, 64 * 1024);
+				
+				if( RC_BAD( rc = f_allocAlignedBuffer( 
+					uiExtendBufferSize, &pucExtendBuffer)))
+				{
+					goto Exit;
+				}
 				
 				while( uiTotalBytesToExtend)
 				{
 					uiCurrBytesToExtend = f_min( 
-										uiTotalBytesToExtend, m_uiAlignedBuffSize);
+									uiTotalBytesToExtend, uiExtendBufferSize);
 					
-					if( (iBytesWritten = pwrite( m_fd, 
-						m_pucAlignedBuff, uiCurrBytesToExtend, 
-						ui64CurrFileSize)) == -1)
+					if( (iBytesWritten = pwrite( m_fd, pucExtendBuffer, 
+						uiCurrBytesToExtend, ui64CurrFileSize)) == -1)
 					{
 						if( errno == EINTR)
 						{
@@ -894,6 +909,11 @@ Exit:
 		f_assert( RC_BAD( rc));
 		pIOBuffer->notifyComplete( rc);
 	}
+	
+	if( pucExtendBuffer)
+	{
+		f_freeAlignedBuffer( &pucExtendBuffer);
+	}
 
 	if( puiBytesWritten)
 	{
diff --git a/ftk/src/ftkwin.cpp b/ftk/src/ftkwin.cpp
index d908791..2647fba 100644
--- a/ftk/src/ftkwin.cpp
+++ b/ftk/src/ftkwin.cpp
@@ -339,6 +339,10 @@ RCODE F_FileHdl::lowLevelRead(
 	{
 		ui64ReadOffset = m_ui64CurrentPos;
 	}
+	else
+	{
+		m_ui64CurrentPos = ui64ReadOffset;
+	}
 	
 	if( !pvBuffer)
 	{
@@ -491,6 +495,10 @@ RCODE F_FileHdl::lowLevelWrite(
 	{
 		ui64WriteOffset = m_ui64CurrentPos;
 	}
+	else
+	{
+		m_ui64CurrentPos = ui64WriteOffset;
+	}
 
 	if( m_bDoDirectIO)
 	{