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Deploy Windows Server on a ReFS boot volume by using Setup unattend (preview)

Important

ReFS boot is currently in PREVIEW. This information relates to a prerelease product that may be substantially modified before it's released. Microsoft makes no warranties, expressed or implied, with respect to the information provided here.

In Windows Server Insider Preview, you can use Resilient File System (ReFS) as the boot volume so that a single file system spans both the operating system and your data volumes. This setup is useful on dedicated storage hosts that already rely on ReFS features such as block cloning and integrity streams. For background on the file system itself, see Resilient File System (ReFS) overview.

ReFS doesn't support volume shrink, so Windows Setup can't create the Windows Recovery Environment (WinRE) partition automatically when you format the OS volume as ReFS. Your unattend answer file must create the WinRE partition explicitly and format it as NTFS.

This article shows you how to author a Windows Setup answer file (unattend.xml) that installs Windows Server Insider Preview onto a ReFS boot volume on a Unified Extensible Firmware Interface (UEFI) and GUID Partition Table (GPT) disk, and how to pre-create the NTFS WinRE partition so the recovery environment works.

Prerequisites

Before you begin, make sure you have the following items:

When to use ReFS for the boot volume

ReFS provides data integrity, scale, and resiliency. Boot Windows Server from ReFS when you want a single file system across the boot volume and data volumes. For example, dedicated storage hosts already rely on ReFS features such as block cloning and integrity streams for their workloads, so extending ReFS to the boot volume keeps the entire host on one file system.

Use NTFS for the boot volume when you need features that ReFS doesn't support on the OS volume. Examples include file-level compression and features that depend on volume shrink.

Validate third-party tooling before broad deployment. Antivirus, backup, and disk-management agents might assume the OS volume is NTFS and fail or behave unexpectedly on a ReFS boot volume.

Plan the partition layout

For a ReFS boot volume on UEFI and GPT, use the following partition layout. The WinRE (Recovery) partition must be NTFS even when the OS volume is ReFS. WinRE itself doesn't run from a ReFS volume.

Order Partition File system Recommended size
1 EFI System Partition (ESP) FAT32 200 MB (512/512e disks) or 300 MB (4Kn disks)
2 Microsoft Reserved (MSR) (none) 16 MB
3 Windows (OS) ReFS Remaining capacity, minus the recovery partition
4 Windows Recovery (WinRE) NTFS 2 GB

Place the recovery partition immediately after the Windows partition. This placement makes it easier to apply future WinRE updates that need a larger partition. For details, see Windows Recovery Environment (WinRE) - Hard drive partitions.

Size each partition correctly up front. ReFS doesn't support volume shrink, so you can't recover space from the OS partition after install to grow the recovery partition.

Create the disk layout

Windows Setup creates the WinRE partition automatically only on NTFS boot volumes, where it shrinks the OS volume on first boot. ReFS doesn't support volume shrink, so on a ReFS boot volume you must lay out all four partitions yourself, including the NTFS WinRE partition.

If you don't create an explicit WinRE partition, Setup installs the OS successfully on ReFS, but WinRE features (automatic repair and BitLocker recovery boot) don't work.

Create the layout in one of two ways. Use the unattend approach (recommended) so Setup performs every step from one answer file. Use the DiskPart approach if you already stage Windows PE on your build hosts and prefer to run Setup by using a minimal answer file.

Author the unattend.xml answer file for a ReFS boot volume

To create an unattend.xml answer file that targets a ReFS boot volume, add the following elements to the Microsoft-Windows-Setup component in the windowsPE configuration pass:

  1. Add a DiskConfiguration > Disk element that targets disk 0 and sets WillWipeDisk to true.

  2. Under CreatePartitions, define the EFI, MSR, OS, and recovery partitions in the order shown in Plan the partition layout.

  3. Under ModifyPartitions, format the OS partition by setting Format to REFS.

  4. In the ModifyPartition element for the recovery partition, set Format to NTFS and set the TypeID attribute to DE94BBA4-06D1-4D40-A16A-BFD50179D6AC to mark it as a Windows Recovery Tools partition.

  5. Under ImageInstall > OSImage > InstallTo, point Setup at the ReFS OS partition (DiskID 0, PartitionID 3).

The following example installs Windows Server to a ReFS partition on disk 0 and creates an NTFS recovery partition for WinRE. Expand the section to view the full answer file.

The 120-GB OS partition size in the following examples is an example configuration, not a requirement. In a typical deployment, size the OS partition to use the remaining disk capacity minus the recovery partition. Adjust the value to suit your hardware.

Example unattend.xml for UEFI and GPT, ReFS boot, and NTFS WinRE 
<?xml version="1.0" encoding="utf-8"?>
<unattend xmlns="urn:schemas-microsoft-com:unattend">
  <settings pass="windowsPE">
    <component name="Microsoft-Windows-Setup"
               processorArchitecture="amd64"
               publicKeyToken="31bf3856ad364e35"
               language="neutral"
               versionScope="nonSxS"
               xmlns:wcm="http://schemas.microsoft.com/WMIConfig/2002/State">

      <DiskConfiguration>
        <Disk wcm:action="add">
          <DiskID>0</DiskID>
          <WillWipeDisk>true</WillWipeDisk>

          <CreatePartitions>
            <!-- 1. EFI System Partition. Use 200 MB on 512/512e disks; use 300 MB on 4Kn disks. -->
            <CreatePartition wcm:action="add">
              <Order>1</Order>
              <Type>EFI</Type>
              <Size>200</Size>
            </CreatePartition>

            <!-- 2. Microsoft Reserved Partition -->
            <CreatePartition wcm:action="add">
              <Order>2</Order>
              <Type>MSR</Type>
              <Size>16</Size>
            </CreatePartition>

            <!-- 3. Windows (OS) partition -->
            <CreatePartition wcm:action="add">
              <Order>3</Order>
              <Type>Primary</Type>
              <!-- Example size only, not a requirement. To fill the disk, set this to (total disk size in MB) - 200 (ESP) - 16 (MSR) - 2048 (recovery). Don't leave trailing unallocated space after the recovery partition. -->
              <Size>120000</Size>
            </CreatePartition>

            <!-- 4. Windows Recovery (WinRE) partition - 2 GB -->
            <CreatePartition wcm:action="add">
              <Order>4</Order>
              <Type>Primary</Type>
              <Size>2048</Size>
            </CreatePartition>
          </CreatePartitions>

          <ModifyPartitions>
            <ModifyPartition wcm:action="add">
              <Order>1</Order>
              <PartitionID>1</PartitionID>
              <Label>System</Label>
              <Format>FAT32</Format>
            </ModifyPartition>

            <ModifyPartition wcm:action="add">
              <Order>2</Order>
              <PartitionID>2</PartitionID>
            </ModifyPartition>

            <!-- OS partition formatted as ReFS -->
            <ModifyPartition wcm:action="add">
              <Order>3</Order>
              <PartitionID>3</PartitionID>
              <Label>Windows</Label>
              <Letter>C</Letter>
              <Format>REFS</Format>
            </ModifyPartition>

            <!-- Recovery partition: NTFS, marked as Windows Recovery Tools. No <Letter> is set, and the recovery TypeID keeps Windows from assigning a drive letter. -->
            <ModifyPartition wcm:action="add">
              <Order>4</Order>
              <PartitionID>4</PartitionID>
              <Label>Recovery</Label>
              <Format>NTFS</Format>
              <TypeID>DE94BBA4-06D1-4D40-A16A-BFD50179D6AC</TypeID>
            </ModifyPartition>
          </ModifyPartitions>
        </Disk>

        <WillShowUI>OnError</WillShowUI>
      </DiskConfiguration>

      <ImageInstall>
        <OSImage>
          <InstallTo>
            <DiskID>0</DiskID>
            <PartitionID>3</PartitionID>
          </InstallTo>
          <InstallToAvailablePartition>false</InstallToAvailablePartition>
        </OSImage>
      </ImageInstall>

    </component>
  </settings>
</unattend>

Important

The Format element of ModifyPartition accepts REFS as a value only in Windows Server Insider Preview builds that include ReFS boot. On other builds, Setup fails the answer-file pass with an invalid format error.

The unattend ModifyPartition schema doesn't set GPT attributes directly. The example doesn't assign a drive letter to the recovery partition and relies on the recovery TypeID (DE94BBA4-06D1-4D40-A16A-BFD50179D6AC) to mark it as a Windows Recovery Tools partition, which Windows doesn't assign a drive letter. To match the DiskPart flow exactly and also set GPT_BASIC_DATA_ATTRIBUTE_NO_DRIVE_LETTER and GPT_ATTRIBUTE_PLATFORM_REQUIRED, apply gpt attributes=0x8000000000000001 to the recovery partition after installation by using DiskPart.

Prepartition the ReFS disk by using DiskPart

Instead of using the unattend DiskConfiguration section, you can lay out the disk yourself in Windows PE by using a DiskPart script. Use the answer file only for the install step. This approach produces the same layout as the unattend example in Author the unattend.xml answer file for a ReFS boot volume.

To prepartition the disk by using DiskPart, create a script with the following commands and run it from Windows PE before starting Setup. Adjust partition sizes as needed.

Warning

The following script runs clean against disk 0, which permanently deletes all partitions and data on that disk. Before you run it, confirm the target disk number by using list disk in DiskPart and update select disk 0 if your boot disk has a different number.

  1. Save the following script as X:\layout.txt in your Windows PE image. The set id command marks the partition with PARTITION_MSFT_RECOVERY_GUID so Windows recognizes it as a recovery partition. The gpt attributes command combines GPT_BASIC_DATA_ATTRIBUTE_NO_DRIVE_LETTER and GPT_ATTRIBUTE_PLATFORM_REQUIRED, which hides the drive letter and prevents accidental modification.

    rem === ReFS boot layout for UEFI and GPT ===
select disk 0
clean
convert gpt

rem 1. EFI System Partition (use size=200 on 512/512e disks; use size=300 on 4Kn disks)
create partition efi size=200
format quick fs=fat32 label="System"
assign letter=S

rem 2. Microsoft Reserved
create partition msr size=16

rem 3. Windows (OS) partition - ReFS (size=120000 is an example only, not a requirement; to fill the disk use (total disk size in MB) - 200 (ESP) - 16 (MSR) - 2048 (recovery), leaving no trailing unallocated space)
create partition primary size=120000
format quick fs=refs label="Windows"
assign letter=C

rem 4. Windows Recovery (WinRE) partition - NTFS, 2 GB, marked as recovery
create partition primary size=2048
format quick fs=ntfs label="Recovery"
assign letter=R
set id="DE94BBA4-06D1-4D40-A16A-BFD50179D6AC"
gpt attributes=0x8000000000000001

list partition
exit

  2. Copy layout.txt onto your Windows PE media (for example, to the root of the USB drive so it's available as X:\layout.txt in WinPE), and then boot the target server from that media into Windows PE. For details on creating WinPE media, see WinPE intro and Copype command-line options.

  3. From the Windows PE command prompt, run DiskPart against the script:

    diskpart /s X:\layout.txt

  4. Run Setup against the ReFS OS partition:

    setup.exe /unattend:X:\unattend.xml

    X:\unattend.xml is an answer file that contains only the ImageInstall section of the example in Author the unattend.xml answer file for a ReFS boot volume. Omit DiskConfiguration because you already partitioned the disk.

Register WinRE on the recovery partition

After Setup completes and Windows boots, register the WinRE image so the recovery tools target the dedicated recovery partition.

  1. Sign in to the new Windows Server installation as an administrator and open an elevated command prompt.

  2. Confirm the current WinRE state:

    reagentc /info

  3. If you laid out the disk with the unattend.xml or DiskPart examples in this article, the recovery partition is hidden and has no drive letter. Temporarily assign one with DiskPart so you can copy files to it. Adjust disk and partition numbers to match your layout:

    select disk 0
select partition 4
assign letter=R
exit

  4. If WinRE is disabled or points to the wrong location, copy winre.wim to the recovery partition and re-register it. Substitute the temporary drive letter you assigned (for example, R) for <RecoveryDrive>. Use the drive letter only, without a colon, because the commands already include the colon:

    mkdir <RecoveryDrive>:\Recovery\WindowsRE
xcopy /h C:\Windows\System32\Recovery\Winre.wim <RecoveryDrive>:\Recovery\WindowsRE\
reagentc /setreimage /path <RecoveryDrive>:\Recovery\WindowsRE /target C:\Windows
reagentc /enable
reagentc /info

  5. Remove the temporary drive letter so the recovery partition stays hidden. Use the same disk and partition numbers as before:

    select disk 0
select partition 4
remove letter=R
exit

  6. Verify that Windows RE status is Enabled and that the location matches the recovery partition.

For more information, see Deploy Windows RE.

Verify the ReFS boot volume

After the server reboots into Windows for the first time, confirm the boot volume is ReFS by using the Get-Volume cmdlet in PowerShell:

Get-Volume -DriveLetter C | Format-List DriveLetter, FileSystemType, Size, SizeRemaining

The FileSystemType value should be ReFS. Alternatively, check from the command line:

fsutil fsinfo volumeinfo C:

Confirm that the output includes the line File System Name : ReFS.

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