Share via

2.2.2 [MS-FSA] File System Algorithms

  • Article

C0004:

Windows 8 operating system, Windows Server 2012 operating system, Windows 8.1 operating system, Windows Server 2012 R2 operating system, Windows 10 operating system, Windows Server 2016 operating system, Windows Server operating system, Windows Server 2019 operating system, Windows Server 2022 operating system, and Windows 11 operating system

If the server doesn't support the FSCTL_OFFLOAD_READ and FSCTL_OFFLOAD_WRITE commands, as specified in [MS-FSA] sections 2.1.5.9.20 and 2.1.5.9.21, then any small computer system interface (SCSI) ODX commands initiated by the virtual machine operating system fail.

If the server supports the FSCTL_OFFLOAD_READ and FSCTL_OFFLOAD_WRITE commands, then Hyper-V can issue these commands to optimize the performance of virtual disk creation, merge, compaction, and mirroring operations.

C0005:

Windows 8, Windows Server 2012, Windows 8.1, Windows Server 2012 R2, Windows 10, Windows Server 2016, Windows Server operating system, Windows Server 2019, Windows Server 2022, and Windows 11

If the server supports the FSCTL_SET_ZERO_DATA command, as specified in [MS-FSA] section 2.1.5.9.39, then Hyper-V can issue this command to optimize the performance of virtual-disk-creation operations.

C0006:

Windows 8, Windows Server 2012, Windows 8.1, Windows Server 2012 R2, Windows 10, Windows Server 2016, Windows Server operating system, Windows Server 2019, Windows Server 2022, and Windows 11

If the server doesn't support the FSCTL_FILE_LEVEL_TRIM command, as specified in [MS-FSA] section 2.1.5.9.6:

  • Support for the SCSI UNMAP command is still advertised to the virtual machine operating system in the response to SCSI INQUIRY commands.

  • SCSI UNMAP requests initiated by the virtual machine operating system are still completed successfully to the virtual machine operating system, but they have no side effects (they are not translated into corresponding file system requests to release space allocated to the files backing the virtual disks attached to the virtual machine).

C0007:

Windows 10, Windows Server 2016, Windows Server operating system, Windows Server 2019, and Windows Server 2022

If the server advertises the FILE_SUPPORTS_BLOCK_REFCOUNTING flag for a given Open (as defined in FILE_FS_ATTRIBUTE_INFORMATION), the server MUST support the FSCTL_DUPLICATE_EXTENTS_TO_FILE command, as specified in [MS-FSA] section 2.1.5.9.4.

C0008:

Windows 8, Windows Server 2012, Windows 8.1, Windows Server 2012 R2, Windows 10, Windows Server 2016, Windows Server operating system, Windows Server 2019, Windows Server 2022, and Windows 11

Hyper-V doesn't support virtual disk files with any of the following flags set, as specified in [MS-FSCC] section 2.6:

  • FILE_ATTRIBUTE_COMPRESSED

  • FILE_ATTRIBUTE_ENCRYPTED

  • FILE_ATTRIBUTE_SPARSE_FILE

C0009:

Windows 10 v1703 operating system, Windows Server operating system, Windows Server 2019, and Windows Server 2022

If the server advertises the FILE_SUPPORTS_SPARSE_VDL flag for a given Open (as specified in [MS-FSCC] section 2.5.1), Hyper-V will support virtual disk files with the FILE_ATTRIBUTE_SPARSE_FILE flag set, as specified in [MS-FSCC] section 2.6.