VHDX | 数据恢复实验室 Data Recovery Laboratory

　　Windows Server 2012的发布带来了虚拟化方面的许多改进，但是VHDX文件格式的推出却引起了许多IT专家的注意。Windows Server 2012支持新的格式，同时允许Hyper-V管理员使用以前的VHD格式。有两种虚拟硬盘格式可供选择，下面是VHD和VHDX的对比。

　　VHD和VHDX简介

　　相对之前的VHD格式，VHDX最大的优势之一在于虚拟硬盘存储容量。在Windows Server 2012之前，Hyper-V虚拟硬盘存在最大2TB的容量限制。而VHDX最大能够达到64TB。而VHDX的优势不只限于容量方面的改进，VHDX为现在的硬盘而设计，相比于VHD文件，其4KB大小的逻辑区域大小有助于提高性能。

　　通过不断监控元数据更新，VHDX还提供在突然断电情况下的文件讹误保护功能，而VHD格式并不具备这个特性。为动态和差分磁盘提供更大的文件块，存储自定义元数据特性，这些都是VHD和VHDX的不同之处。

　　转换为VHDX格式

　　首先，需要知道的是可以在Windows Server 2012上创建和使用两种格式，但是VHDX文件和Windows Server 2008并不兼容。微软推荐大多数Windows Server 2012用户将VHD文件升级到VHDX，以使用其中的各种新特性。但是，如果你希望将虚拟机移动到之前版本的Windows Server上，那么使用VHD文件会更加方便。用户可以在Hyper-V中的编辑虚拟硬盘向导中将VHD文件转换为VHDX文件。

Windows 8中支持的VHDX虚拟磁盘格式，以下是虚拟磁盘结构代码。

//Structure 1: File Type Identifier
struct VHDX_FILE_IDENTIFIER {
	UINT64 	Signature;
	UINT16 	Creator[256];
};

//Structure 2: Header
struct VHDX_HEADER {
	UINT32 	Signature;
	UINT32 	Checksum;
	UINT64 	SequenceNumber;
	GUID 		FileWriteGuid;
	GUID 		DataWriteGuid;
	GUID 		LogGuid;
	UINT16 	LogVersion;
	UINT16 	Version;
	UINT32 	LogLength;
	UINT64 	LogOffset;
	UINT8[502] 	Reserved;
};

//Structure 3: Region Table Header
struct VHDX_REGION_TABLE_HEADER {
	UINT32 	Signature;
	UINT32 	Checksum;
	UINT32 	EntryCount;
	UINT32 	Reserved;
};

//Structure 4: Region Table Entry
struct VHDX_REGION_TABLE_ENTRY {
	GUID 		Guid;
	UINT64 	FileOffset;
	UINT32 	Length;
	UINT32 	Required:1;
	UINT32 	Reserved:31;
};

//Structure 5: Log Entry Header
struct VHDX_LOG_ENTRY_HEADER {
	UINT32 	Signature;
	UINT32 	Checksum;
	UINT32 	EntryLength;
	UINT32 	Tail;
	UINT64 	SequenceNumber;
	UINT32 	DescriptorCount;
	UINT32 	Reserved;
	GUID 		LogGuid;
	UINT64 	FlushedFileOffset;
	UINT64 	LastFileOffset;
};

//Structure 6: Log Zero Descriptor
struct VHDX_LOG_ZERO_DESCRIPTOR {
	UINT32 	ZeroSignature;
	UINT32 	Reserved;
	UINT64 	ZeroLength;
	UINT64 	FileOffset;
	UINT64 	SequenceNumber;
};

//Structure 7: Log Data Descriptor
struct VHDX_LOG_DATA_DESCRIPTOR {
	UINT32 	DataSignature;
	UINT32 	TrailingBytes;
	UINT64 	LeadingBytes;
	UINT64 	FileOffset;
	UINT64 	SequenceNumber;
};

//Structure 8: Log Data Sector
struct VHDX_LOG_DATA_SECTOR {
	UINT32 	DataSignature;
	UINT32 	SequenceHigh;
	UINT8 	Data[4084];
	UINT32 	SequenceLow;
};

//Structure 9: BAT Entry
struct VHDX_BAT_ENTRY {
	UINT64 	State:3;
	UINT64 	Reserved:17;
	UINT64 	FileOffsetMB:44;
};

//Structure 10: Metadata Table Header
struct VHDX_METADATA_TABLE_HEADER {
	UINT64 	Signature;
	UINT16 	Reserved;
	UINT16 	EntryCount;
	UINT32 	Reserved2[5];
};

//Structure 11: Metadata Table Entry
struct VHDX_METADATA_TABLE_ENTRY {
	GUID	 	ItemId;
	UINT32 	Offset;
	UINT32 	Length;
	UINT32 	IsUser:1;
	UINT32 	IsVirtualDisk:1;
	UINT32 	IsRequired:1;
	UINT32 	Reserved:29;
	UINT32 	Reserved2;
};

//Structure 12: File Parameters Metadata Item
struct VHDX_FILE_PARAMETERS {
	UINT32 	BlockSize;
	UINT32 	LeaveBlocksAllocated:1;
	UINT32 	HasParent:1;
	UINT32 	Reserved:30;
};

//Structure 13: Virtual Disk Size Metadata Item
struct VHDX_VIRTUAL_DISK_SIZE {
	UINT64 	VirtualDiskSize;
};

//Structure 14: Page 83 Data Metadata Item
struct VHDX_PAGE83_DATA {
	GUID 		Page83Data;
};

//Structure 15: Logical Sector Size Metadata Item
struct VHDX_VIRTUAL_DISK_LOGICAL_SECTOR_SIZE {
	UINT32 	LogicalSectorSize;
};

//Structure 16: Logical Sector Size Metadata Item
struct VHDX_VIRTUAL_DISK_PHYSICAL_SECTOR_SIZE {
	UINT32 	PhysicalSectorSize;
};

//Structure 17: Parent Locator Header
struct VHDX_PARENT_LOCATOR_HEADER {
	GUID 		LocatorType;
	UINT16 	Reserved;
	UINT16 	KeyValueCount;
};

//Structure 18: Parent Locator Entry
struct VHDX_PARENT_LOCATOR_ENTRY {
	UINT32 	KeyOffset;
	UINT32 	ValueOffset;
	UINT16 	KeyLength;
	UINT16 	ValueLength;
};

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//Structure 1: File Type Identifier

struct VHDX_FILE_IDENTIFIER {

UINT64 Signature;

UINT16 Creator[256];

};

//Structure 2: Header

struct VHDX_HEADER {

UINT32 Signature;

UINT32 Checksum;

UINT64 SequenceNumber;

GUID FileWriteGuid;

GUID DataWriteGuid;

GUID LogGuid;

UINT16 LogVersion;

UINT16 Version;

UINT32 LogLength;

UINT64 LogOffset;

UINT8[502] Reserved;

};

//Structure 3: Region Table Header

struct VHDX_REGION_TABLE_HEADER {

UINT32 Signature;

UINT32 Checksum;

UINT32 EntryCount;

UINT32 Reserved;

};

//Structure 4: Region Table Entry

struct VHDX_REGION_TABLE_ENTRY {

GUID Guid;

UINT64 FileOffset;

UINT32 Length;

UINT32 Required:1;

UINT32 Reserved:31;

};

//Structure 5: Log Entry Header

struct VHDX_LOG_ENTRY_HEADER {

UINT32 Signature;

UINT32 Checksum;

UINT32 EntryLength;

UINT32 Tail;

UINT64 SequenceNumber;

UINT32 DescriptorCount;

UINT32 Reserved;

GUID LogGuid;

UINT64 FlushedFileOffset;

UINT64 LastFileOffset;

};

//Structure 6: Log Zero Descriptor

struct VHDX_LOG_ZERO_DESCRIPTOR {

UINT32 ZeroSignature;

UINT32 Reserved;

UINT64 ZeroLength;

UINT64 FileOffset;

UINT64 SequenceNumber;

};

//Structure 7: Log Data Descriptor

struct VHDX_LOG_DATA_DESCRIPTOR {

UINT32 DataSignature;

UINT32 TrailingBytes;

UINT64 LeadingBytes;

UINT64 FileOffset;

UINT64 SequenceNumber;

};

//Structure 8: Log Data Sector

struct VHDX_LOG_DATA_SECTOR {

UINT32 DataSignature;

UINT32 SequenceHigh;

UINT8 Data[4084];

UINT32 SequenceLow;

};

//Structure 9: BAT Entry

struct VHDX_BAT_ENTRY {

UINT64 State:3;

UINT64 Reserved:17;

UINT64 FileOffsetMB:44;

};

//Structure 10: Metadata Table Header

struct VHDX_METADATA_TABLE_HEADER {

UINT64 Signature;

UINT16 Reserved;

UINT16 EntryCount;

UINT32 Reserved2[5];

};

//Structure 11: Metadata Table Entry

struct VHDX_METADATA_TABLE_ENTRY {

GUID ItemId;

UINT32 Offset;

UINT32 Length;

UINT32 IsUser:1;

UINT32 IsVirtualDisk:1;

UINT32 IsRequired:1;

UINT32 Reserved:29;

UINT32 Reserved2;

};

//Structure 12: File Parameters Metadata Item

struct VHDX_FILE_PARAMETERS {

UINT32 BlockSize;

UINT32 LeaveBlocksAllocated:1;

UINT32 HasParent:1;

UINT32 Reserved:30;

};

//Structure 13: Virtual Disk Size Metadata Item

struct VHDX_VIRTUAL_DISK_SIZE {

UINT64 VirtualDiskSize;

};

//Structure 14: Page 83 Data Metadata Item

struct VHDX_PAGE83_DATA {

GUID Page83Data;

};

//Structure 15: Logical Sector Size Metadata Item

struct VHDX_VIRTUAL_DISK_LOGICAL_SECTOR_SIZE {

UINT32 LogicalSectorSize;

};

//Structure 16: Logical Sector Size Metadata Item

struct VHDX_VIRTUAL_DISK_PHYSICAL_SECTOR_SIZE {

UINT32 PhysicalSectorSize;

};

//Structure 17: Parent Locator Header

struct VHDX_PARENT_LOCATOR_HEADER {

GUID LocatorType;

UINT16 Reserved;

UINT16 KeyValueCount;

};

//Structure 18: Parent Locator Entry

struct VHDX_PARENT_LOCATOR_ENTRY {

UINT32 KeyOffset;

UINT32 ValueOffset;

UINT16 KeyLength;

UINT16 ValueLength;

};

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标签归档：VHDX

VHD和VHDX：虚拟硬盘格式的区别

VHDX 虚拟磁盘格式结构