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Windows 7: Partition question : Unallocated Space Before

20 Dec 2011   #11
mx320

Windows 7 Ultimate 32 bit
 
 
Unalocated space

When you wipe a drive and restore your system, the drive still has partitions setup before hand. These are the general run of the mill storage for your system and progs. but that little 'unallocated' space is for the system itself.
When you start to re-install your OS you should be given a chance to delete these and even format them.
Go to the 'advanced' button and click, you now have the choice of a few things. I always click on the partition I want to work with then format and delete it (just to make sure).
Each time a partition is deleted it becomes 'unalocated space'. If all are deleted you end up with a completely empty drive.
Now you can opt for the allocation button, make your partitions, select which to put your OS on and then "Bob's your uncle".
Hope this works for you as it has for me in the past (this afternoon in fact !)


My System SpecsSystem Spec
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20 Dec 2011   #12
dsperber

Windows 7 Pro x64 (1), Win7 Pro X64 (2)
 
 

Quote   Quote: Originally Posted by Golden View Post
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). Dsperber's disk theory post is what I was after.
Just to be a bit more technically precise with wording... it's not a "logical disk" or a "primary disk". It's a "logical partition" or a "primary partition".

To repeat the key facts: the "physical disk" (or hard drive) contains one or more partitions, and they can be of partition type "logical" or partition type "primary". The drive can contain up to four "primary" partitions, one of which can be used as an "extended" partition inside of which can be any number of "logical" partitions. You are not required to have any true "primary" partitions (with drive letters assigned) if you don't want to. Instead, the drive can contain only one "extended" partition with any number of "logical" partitions inside of it, if you want it that way. Perfectly fine.

However if you want to have a true bootable partition on a drive (e.g. for WinXP, or the "system reserved" boot manager partition for Win7) then that partition MUST be of type "primary". It also needs to be marked "active" so that the BIOS knows to use it as part of the boot process. An "active" partition used for the boot process cannot be type "logical", but can only be type "primary". But if you don't have or need a bootable partition on a drive, then you don't need any true "primary" partitions, and you can have just one single "extended" partition with one or more "logical" partitions inside of it.

The odd small piece of "unallocated" storage (usually about 7.8MB or 10.2MB) which is directly related to the existence of an "extended" partition on the drive (i.e. that there is at least one "logical"partition defined on the drive) doesn't necessarily show up at the start or end of the drive. It's more a matter of how you defined the partitions on that drive, and the sequence you did things in, and whether the partitioning was done manually by you (using DISKMGMT or Partition Wizard, etc.) or by a Windows installer.

So if you delete all existing partitions on a drive to make it completely "unallocated" (or you take a brand new drive out of the carton and use it), and you allocate your very first partition on that drive as "logical", the 7.8MB piece will show up at the front of the drive, before the "extended' partition created so that this first "logical" partition can then be sub-defined inside of it.

But if your first defined partition is "primary" (or you install Windows on an all-unallocated drive), the first partition (OS for WinXP, "system reserved" for Win7) will begin right at the very beginning of the drive. Only if you then create a "logical" partition in the remaining space will the small "unallocated" piece now be created, and will likely be placed at the end of the drive (but I'm not completely positive).

What's important is that you don't need to be concerned at all about this little piece of "unallocated". You can't avoid it, and you can't control it or where it gets placed. The disk management services handle it and that's all we really need to know or care about.


Quote:
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.
Absolutely correct.
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20 Dec 2011   #13
Golden
Microsoft MVP

Windows 7 Ult. x64
 
 

Great stuff - I've taken note of the correct terminology of disk and partition. Thanks again Dsperber
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17 Mar 2015   #14
119baystate

WIN 7 32 bit
 
 

Quote   Quote: Originally Posted by dsperber View Post
Quote   Quote: Originally Posted by Golden View Post
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?
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.
I recently shrunk my system partition to create another partition to make a CLEAN INSTALL system on the new partition. I noticed afterward that I have 1Mb UNALLOCATED space both at the beginning & end of that hard drive. Does your explanation above account for this? I cannot seem to get rid of those 2 spaces.
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17 Mar 2015   #15
dsperber

Windows 7 Pro x64 (1), Win7 Pro X64 (2)
 
 

Quote   Quote: Originally Posted by 119baystate View Post
I recently shrunk my system partition to create another partition to make a CLEAN INSTALL system on the new partition. I noticed afterward that I have 1Mb UNALLOCATED space both at the beginning & end of that hard drive. Does your explanation above account for this? I cannot seem to get rid of those 2 spaces.
Can you please post a screenshot from DISKMGMT.MSC, so that your hard drive can be shown by picture. Please spread the columns in the upper part of the window so that we can read all the text in the cells.
My System SpecsSystem Spec
17 Mar 2015   #16
119baystate

WIN 7 32 bit
 
 

Quote   Quote: Originally Posted by dsperber View Post
Quote   Quote: Originally Posted by 119baystate View Post
I recently shrunk my system partition to create another partition to make a CLEAN INSTALL system on the new partition. I noticed afterward that I have 1Mb UNALLOCATED space both at the beginning & end of that hard drive. Does your explanation above account for this? I cannot seem to get rid of those 2 spaces.
Can you please post a screenshot from DISKMGMT.MSC, so that your hard drive can be shown by picture. Please spread the columns in the upper part of the window so that we can read all the text in the cells.
DISKMGR does not show the unallocated space, but PARTITION WIZARD does. The spaces in question are boxed in RED. You will need to magnify the view if you need to see detail. The 1st space is 1Mb while the last is 593kb.


Attached Thumbnails
Partition question : Unallocated Space Before-screenshot.jpg  
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17 Mar 2015   #17
119baystate

WIN 7 32 bit
 
 

Any further thoughts or explanations?
My System SpecsSystem Spec
17 Mar 2015   #18
dsperber

Windows 7 Pro x64 (1), Win7 Pro X64 (2)
 
 

I wonder if this is indicative of your partitions not being "aligned", as they should be for optimal performance... HD or SSD.

You can use this quick utility to test for proper partition alignment (although a from-scratch Win7 install on an completely empty drive will always create properly aligned partitions, something which wasn't true with WinXP).

And of course, you can use the Partition Wizard "align all partitions" function to perform necessary alignment. I don't know if it will prompt you first and require your confirmation (probably), after investigating for itself whether or not it's needed.

Anyway, I've never seen your symptom before. Did you use Partition Wizard to resize your partitions, or did you use DISKMGMT? If it was PW, I'm surprised this could have been the result.
My System SpecsSystem Spec
18 Mar 2015   #19
119baystate

WIN 7 32 bit
 
 

Quote   Quote: Originally Posted by dsperber View Post
I wonder if this is indicative of your partitions not being "aligned", as they should be for optimal performance... HD or SSD.

You can use this quick utility to test for proper partition alignment (although a from-scratch Win7 install on an completely empty drive will always create properly aligned partitions, something which wasn't true with WinXP).

And of course, you can use the Partition Wizard "align all partitions" function to perform necessary alignment. I don't know if it will prompt you first and require your confirmation (probably), after investigating for itself whether or not it's needed.

Anyway, I've never seen your symptom before. Did you use Partition Wizard to resize your partitions, or did you use DISKMGMT? If it was PW, I'm surprised this could have been the result.
I did use PARTITION WIZARD. Fortunately, I think I stumbled onto the solution, but I do not know exactly how. I ended up in CMD mode to WIPE out the 2nd system partition & then rebooted. It was taking forever which my guess it was looking for both system partitions in the MBR. Chalk this up to impatience. I powered down the computer in the process. Knowing that I probably FREAKED out the boot sequence I simply restored the old image. The 2 unallocated spaces are GONE.

I am in the middle of shrinking down the system partition to create the new one for a CLEAN INSTALL. I will report back on the results.
My System SpecsSystem Spec
18 Mar 2015   #20
119baystate

WIN 7 32 bit
 
 

OK, the results are in & the WINNER:

NO UNALLOCATED SPACES!!!!!!!!!!!!!!!!!!!!!!!!!!

Let me ask you this. I am positive that I have resized system partitions before without having to boot from a rescue or system boot CD. In doing so PARTITION WIZARD would require a RESTART to execute the procedure. Upon restart you would see the display information on what the PARTITION WIZARD was doing. On this particular computer that did not happen & when the computer rebooted the system partition did not change in size.

Now at that time I do not recall if the 2 unallocated spaces were present, but that may be the case. What you saw in my screenshot was my shrinking the system partition after booting from a rescue CD.

So if I ever want to change the system partition should I always boot from a system CD instead of running PARTITION WIZARD in "normal" system mode?
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 Partition question : Unallocated Space Before




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