Q. How can I check the starting offset of my NTFS volumes on disk?

A. To help align volumes with physical sectors, an offset is used on volumes to give better alignment. You can use wmic to check the offset of partitions, as shown here.

C:\>wmic partition get Index, Name, StartingOffset

Index Name StartingOffset
0 Disk #1, Partition #0 1048576
1 Disk #1, Partition #1 105906176
2 Disk #1, Partition #2 266199891968
0 Disk #2, Partition #0 32256
0 Disk #3, Partition #0 32256
0 Disk #4, Partition #0 32256
0 Disk #5, Partition #0 32256
0 Disk #0, Partition #0 1048576

Note that when you have multiple partitions on one disk, you get very large offsets on the additional partitions, because they start later in the disk. It's the offset of the first partition on each disk that's important. Pretty much every disk today will use an alignment of 1048576, which is the value for disks over 4GB in size. You can check the offset defaults by looking in the registry at HKLM \SYSTEM\CurrentControlSet\services\vds\Alignment. You can view the block size used by adding blocksize to the wmic command above.

Notice in my example that I have four disks that all have an offset of 32256. They're 1TB disks, so why aren't they offset with 1048576? Those four disks are dynamic disks, which behave differently from basic disks. To check them, you can use the detail part command in diskpart once you've selected the partition that represents the dynamic disk. For example,

DISKPART> detail part

Partition 1
Type : 42
Hidden: Yes
Active: No
Offset in Bytes: 32256

There is no volume associated with this partition.

Note that you still have 32256 as the offset.

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