For those of you installing w10 on unpartitioned space

I clean installed w10 yesterday and remember someone on this forum suggesting installing Windows on unpartitioned space (Windows installer will partition drive as it sees fit). Well, for me, it didn't end too well.

UEFI partition style. (On a 256GB SSD)

1st partition -> EFI (100MB). Small cluster used, so partition wasn't properly 4k aligned.
2nd partition -> OS. Ok. But no MSR partition.
3rd partition -> Recovery partition. I prefer to reallocate those on the OS partition.

After tinkering with Macrium Reflect. I cleaned the whole disk and recreated all partitions. Thus:

1st partition -> EFI (260 MB). 4k cluster sign for proper alignment.
2nd partition -> MSR partition (16 MB).
3rd partition -> OS (and recovery folder). 75GB
4th partition -> User data. All remaining space.

In 2020, I installed Windows in the above "Unallocated Space" and got the following partitions:

Compumind said:

The EFI partition is completely unnecessary for an SSD. There is no 4K alignment of an SSD, only HDD.

Whether or not an EFI System Partition is required or not has absolutely nothing to do with whether it is on an SSD or HDD. An EFI System Partition is required for computers that will not boot from an NTFS partition in UEFI mode. Many computers will only boot in UEFI mode from a FAT partition. If you are lucky enough to have a computer that will boot in UEFI mode from an NTFS partition, then you can put the boot files in your OS partition and the EFI System Partition is optional.

Matthew Wai said:

In 2020, I installed Windows in the above "Unallocated Space" and got the following partitions:

That is also what I have on my drive.

For the 16M MR partition not showing, Windows Disk Manager is very inaccurate. It doesn't show 16M MR partition and some partitions data are showed wrong.

DiskPart shows the following:

Code:

  Volume ###  Ltr  Label        Fs     Type        Size     Status     Info
  ----------  ---  -----------  -----  ----------  -------  ---------  --------
  Volume 1     C   Windows 10   NTFS   Partition     80 GB  Healthy    Boot    
  Volume 2     D   Data         NTFS   Partition    384 GB  Healthy            
  Volume 3                      FAT32  Partition    100 MB  Healthy    System  
  Volume 4         Recovery     NTFS   Partition    499 MB  Healthy    Hidden  

  Partition ###  Type              Size     Offset
  -------------  ----------------  -------  -------
  Partition 1    System             100 MB  1024 KB
  Partition 2    Reserved            16 MB   101 MB
  Partition 3    Primary             80 GB   117 MB
  Partition 4    Recovery           499 MB    80 GB
  Partition 5    Primary            384 GB    81 GB

PowerShell shows the following:

Code:

Drive
Letter   Drive Label     Fs   Free Space Used Space  Capacity   Free
------ --------------- ------ ---------- ---------- ---------- -----
       Recovery        NTFS     83.69 MB  415.31 MB  499.00 MB  17 %
                       FAT32    69.49 MB   26.51 MB   96.00 MB  72 %
  C    Windows 10      NTFS     47.62 GB   32.78 GB   80.40 GB  59 %
  D    Data            NTFS    324.87 GB   59.89 GB  384.76 GB  84 %

I've done a hundred or more Windows 10/11 installs and they are always the same (on an unallocated drive):
100 MB EFI System Partition (FAT32)
16 MB MSR Partition (which will not appear in disk management)
XXXX GB OS partition for the OS
499 MB Recovery Partition