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STORAGE_ACCESS_ALIGNMENT_DESCRIPTOR structure

Used in conjunction with the IOCTL_STORAGE_QUERY_PROPERTY control code to retrieve the storage access alignment descriptor data for a device.

Syntax

C++


typedef struct _STORAGE_ACCESS_ALIGNMENT_DESCRIPTOR {
  DWORD Version;
  DWORD Size;
  DWORD BytesPerCacheLine;
  DWORD BytesOffsetForCacheAlignment;
  DWORD BytesPerLogicalSector;
  DWORD BytesPerPhysicalSector;
  DWORD BytesOffsetForSectorAlignment;
} STORAGE_ACCESS_ALIGNMENT_DESCRIPTOR, *PSTORAGE_ACCESS_ALIGNMENT_DESCRIPTOR;

Members

Version

Contains the size of this structure, in bytes. The value of this member will change as members are added to the structure.

Size

Specifies the total size of the data returned, in bytes. This may include data that follows this structure.

BytesPerCacheLine

The number of bytes in a cache line of the device.

BytesOffsetForCacheAlignment

The address offset necessary for proper cache access alignment, in bytes.

BytesPerLogicalSector

The number of bytes in a logical sector of the device.

BytesPerPhysicalSector

The number of bytes in a physical sector of the device.

BytesOffsetForSectorAlignment

The logical sector offset within the first physical sector where the first logical sector is placed, in bytes.

Example: Offset = 3 Logical sectors

+---------+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|LBA      |##|##|##|00|01|02|03|04|05|06|07|08|09|10|11|12|13|14|15|16|17|
+---------+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|Physical |                       |                       |                ...
|Sector   |           0           |           1           |           2
+---------+-----------------------+-----------------------+---------------

In this example, BytesOffsetForSectorAlignment = 3 * BytesPerLogicalSector.

Examples

The following sample code retrieves a STORAGE_ACCESS_ALIGNMENT_DESCRIPTOR structure and displays the physical sector size and the logical sector size if it differs from the physical sector size.

C++


#include <windows.h>
#include <stdio.h>

DWORD DetectSectorSize( WCHAR * devName, PSTORAGE_ACCESS_ALIGNMENT_DESCRIPTOR pAlignmentDescriptor);

DWORD wmain()
 {
  DWORD                               Error     = NO_ERROR;
  STORAGE_ACCESS_ALIGNMENT_DESCRIPTOR Alignment = {0};
  WCHAR                               szDisk[]  = L"\\\\.\\PhysicalDrive0";

  Error = DetectSectorSize(szDisk, &Alignment);
  if (Error)
   {
    wprintf(L"Error %lu encountered while querying alignment.\n", Error);
    return Error;
   }

  wprintf(L"Disk %s Properties\n", (WCHAR*) szDisk);

  if (Alignment.BytesPerLogicalSector < Alignment.BytesPerPhysicalSector)
   {
    wprintf(L"  Emulated sector size is %lu bytes.\n", Alignment.BytesPerLogicalSector);
    wprintf(L"  Physical sector size is %lu bytes.\n", Alignment.BytesPerPhysicalSector);
   }
   else
   {
    wprintf(L"  Physical sector size is %lu bytes.\n", Alignment.BytesPerPhysicalSector);
   }

  return 0;
 }

DWORD DetectSectorSize( WCHAR * devName, PSTORAGE_ACCESS_ALIGNMENT_DESCRIPTOR pAlignmentDescriptor)
 {
  DWORD                  Bytes   = 0;
  BOOL                   bReturn = FALSE;
  DWORD                  Error   = NO_ERROR;
  STORAGE_PROPERTY_QUERY Query;
  
  ZeroMemory(&Query, sizeof(Query));

  HANDLE  hFile = CreateFileW( devName,
                               STANDARD_RIGHTS_READ, 
                               FILE_SHARE_READ | FILE_SHARE_WRITE,
                               NULL, 
                               OPEN_EXISTING, 
                               FILE_ATTRIBUTE_NORMAL,
                               NULL);

  if (hFile==INVALID_HANDLE_VALUE)
   {
    Error=GetLastError();
    return Error;
   }

  Query.QueryType  = PropertyStandardQuery;
  Query.PropertyId = StorageAccessAlignmentProperty;
      
  bReturn = DeviceIoControl( hFile, 
                             IOCTL_STORAGE_QUERY_PROPERTY, 
                             &Query, 
                             sizeof(STORAGE_PROPERTY_QUERY), 
                             pAlignmentDescriptor,
                             sizeof(STORAGE_ACCESS_ALIGNMENT_DESCRIPTOR), 
                             &Bytes,
                             NULL);

  if (bReturn == FALSE)
   {
    Error=GetLastError();
   }

  CloseHandle(hFile);
  return Error;

 }

Requirements

Minimum supported client	Windows Vista [desktop apps only]
Minimum supported server	Windows Server 2008 [desktop apps only]
Header	WinIoCtl.h (include Windows.h)

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