Windows 7 - Partition question : Unallocated Space Before

G'day Fella's,

I'm using EASEUS Partition Master Home Edition to create a single Logical partition on a WD10EARS-00Y5B1 1TB HDD. After wiping the disk completely, and selecting to create a single NTFS partition, I note that there is a 7.8MB unallocated space at the front of the disk (see image).

Can someone explain what this space is, and why it is unallocated?

Thanks,
Golden

The 7.8MB unallocated space was before you partitioned the drive as your pic shows that the 7.8MB unallocated space is 0 after, no problems to worry about there mate.

I believe the before and after we are looking at refers to where it is located on the disc in relation to the new partition (did that make sense?).

Golden, I am really not sure about this one. It looks like you can adjust those numbers. Is there anyway to make that amount smalller? Is there a possibility of it being bad sectors being left out of the partition? Can you try doing it in disk managment? For some reason it wants that space unallocated. For some reason it wants that space to be free. It's only 7.4 MB. You might just want let it be.

I'm pretty sure it is the size and not the location, if you slide either side of that partition in it will give you before and after sizes.

Alright then. I'm not all-to familiar with Partition Master. I was assuming what it was based on Golden's post.

Yeah, it's hard to tell which end had the unallocated space in his screenshot since the slider is already moved to the end.

Need just a little explanation here about disk theory.

A "logical" partition is defined inside of what's called an "extended partition", which is a special purpose "primary" partition inside of which one or more "logical" partitions can be sub-defined.

A basic MBR hard drive can support up to four primary partitions, and any one of them can be used as an "extended" partition so that one or more "logical" partitions can be sub-defined inside of it.

So you can have three real "primary" partitions, and one "extended" partition inside of which any number of "logical" partitions can then be sub-defined. Of course you can also have ZERO real "primary" partitions and just one "extended" partition on your drive (as you've done), so that all partitions defined on that drive are "logical" and located within the one single "extended" partition.

The "extended" partition has some control information (think of it as sort of a "prefix") which lives outside of real data area that's used by the "logical" partitions inside of it. This "prefix" isn't very large, but needs to exist. Since space allocation on a drive is in sector group units of 8MB, just one 8MB allocation unit is sufficient to hold the "prefix" information associated with the "extended" partition. But once it's been partially consumed for that purpose, the remainder of that 8MB is unavailable for further allocation since space allocation is in complete 8MB units.

===>> That's why you see 7.8MB "unallocated", because .2MB of that 8MB unit of space has been used for the "prefix" information tied to the one "extended" partition inside of which your "logical" partitions live.

Don't worry about it. That's perfectly normal and by design. You will not be able to make use of this 7.8MB for any purpose.

You dont need to worry about that as same 7.8MB unallocated space is on my had shown by easus

Just some more interesting examples of this small "unallocated" space tied to the presence of an "extended" partition on a drive, depending on the order in which you defined your partitions (some primary, some logical, at the start of free-space, at the end of free-space, etc.)...

(1) it doesn't have to PRECEDE the "extended" partition. It can also be located AFTER the "extended" partition.



(2) it doesn't even have to be CONSECUTIVE (i.e. adjacent) to the "extended" partition. It can actually be SEPARATED from the "extended" partition by a primary partition!




Bottom line: forget about it. This is simply part of primary/logical partition architecture.

Excellent - thanks guys. It was more about the why the 7.8MB (in logical disks its always at the front of the disk, in primary disks its always 10MB at the back of the disk). Desperber's disk theory post is what I was after.

In Windows Disk Management you never see the unallocated space graphically - it only shows up in more advanced partioning software such as EASEUS and Partition Wizard MiniTool.

Thanks again.