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Windows 7: The 100mb (or was it gb) boot partition - query


07 Oct 2010   #1

W7 Home Prem, Vista home Prem
 
 
The 100mb (or was it gb) boot partition - query

Hi,

Just read a tutorial on here about optimising hdd performance in Windows 7. It talks about doing a disk wipe and then creating a boot partition using diskpart so you don't end up with the 'dreaded' 100mb (or was it gb) boot partition

My question really is what was so dreadful about this boot partition. Due to being a little naive - I'm not even sure what problems this tutorial is solving! Thanks
Matt

My System SpecsSystem Spec
.

07 Oct 2010   #2
whs
Microsoft MVP

Vista, Windows7, Mint Mate, Zorin, Windows 8
 
 

There is nothing dreadful about the 100MB partition. Seperating the MBR from the system is in fact a good idea - just think of a double boot. The downside though is that it takes up a primary partition and this together with the C and D partitions and a possible tools partition (in preinstalled OEM systems) saturates the system (4 primaries maximum in NTFS). Many people then do not know how to get out of this bind if they want to create an extra partition (e.g. a Data Partition) - many people who are not aware of the problem run into the dreaded dynamic partitions. But there are, of course, ways how to deal with it - not easy, but possible.

In an installation with a retail Windows 7 one does not have this problem because there is no D (recovery) partition and no tools partition. There the extra 100MBs really do not hurt.
My System SpecsSystem Spec
07 Oct 2010   #3

W7 Home Prem, Vista home Prem
 
 

Ahh. My thanks for the explanation - the history makes sense of the present. Didn't know about the 4 max limit either.

Cheers
My System SpecsSystem Spec
.


07 Oct 2010   #4
Microsoft MVP

W 7 64-bit Ultimate
 
 

The original idea to do away with the dreaded 100MB boot partition was to reclaim as much space as possible from Solid State Drives (SSD) that had a small over-all size to start with; the "clean all" part of the tutorial has since shown it's worth in helping resolve installation issues where old Windows code being present is interfering with the installation process.

No problem, you won't know if you don't ask!



If you need a fourth "Primary" have a look at Option One of this tutorial.

Partition Wizard : Use the Bootable CD
My System SpecsSystem Spec
07 Oct 2010   #5
mjf

Windows 7x64 Home Premium SP1
 
 

I can only see 2 downsides to the separate 100MB partition:
1) Uses one of the 4 disk partitions. You can still use logical partitions if you want lots of partitions for some reason.
2) For some reason (which I don't understand) the 100MB partition can fill to greater than 50MB. When this happens you have problems with Windows imaging.

If 1) or 2) aren't of concern then I would just leave it alone but recognize that it contains the boot manager and the boot configuration data (BCD). It's critical to the booting of your computer.

The MBR (Master Boot Record) does not live in this 100MB partition. For BIOS booted PCs it is the first sector of the first track of the boot disk (first 512 bytes of the boot device inc USBs). It has a fixed physical location as well as data format.
My System SpecsSystem Spec
07 Oct 2010   #6
Microsoft MVP

W 7 64-bit Ultimate
 
 

Quote   Quote: Originally Posted by mjf View Post
I can only see 2 downsides to the separate 100MB partition:
1) Uses one of the 4 disk partitions. You can still use logical partitions if you want lots of partitions for some reason.
2) For some reason (which I don't understand) the 100MB partition can fill to greater than 50MB. When this happens you have problems with Windows imaging.

If 1) or 2) aren't of concern then I would just leave it alone but recognize that it contains the boot manager and the boot configuration data (BCD). It's critical to the booting of your computer.

The MBR (Master Boot Record) does not live in this 100MB partition. For BIOS booted PCs it is the first sector of the first track of the boot disk (first 512 bytes of the boot device inc USBs). It has a fixed physical location as well as data format.

There's an option to create a larger "System Reserved" and place it where you want and mark it "Active" before you start the Windows 7 install so that space won't be an issue, using the Partition Wizard boot disk.

Partition Wizard : Use the Bootable CD
click to enlarge
The 100mb (or was it gb) boot partition - query-sr-second.jpg
The 100mb (or was it gb) boot partition - query-system-reserved.jpg



My System SpecsSystem Spec
08 Oct 2010   #7
Microsoft MVP

 

Quote   Quote: Originally Posted by mjf View Post
I2) For some reason (which I don't understand) the 100MB partition can fill to greater than 50MB. When this happens you have problems with Windows imaging.
This seems to be the result of the drive having a letter, the only way anything can write to it as far as I know.

I would resist giving it a letter.
My System SpecsSystem Spec
08 Oct 2010   #8
mjf

Windows 7x64 Home Premium SP1
 
 

Quote   Quote: Originally Posted by gregrocker View Post
Quote   Quote: Originally Posted by mjf View Post
I2) For some reason (which I don't understand) the 100MB partition can fill to greater than 50MB. When this happens you have problems with Windows imaging.
This seems to be the result of the drive having a letter, the only way anything can write to it as far as I know.

I would resist giving it a letter.
You shouldn't assign a letter to the System reserved partition. It's not for users to write to except when using tools like bcdedit to edit the boot configuration data. The OS can write to it.

Quote from Microsoft technical information:
"System Partition Requirements

Basic system partition requirements are:
  • Must have at least 100 megabytes (MB) of hard drive space.

  • Must have enough free space to create shadow copies of the partition.

    • If the partition is less than 500 MB, it must have at least 50 MB of free space.

    • If the partition is 500 MB or larger, it must have at least 320 MB of free space.

    • If the partition is larger than 1 gigabyte (GB), we recommend that it should have at least 1 GB free."
I thought this only applied to UEFI but clearly applies to BIOS boot as well. As stated the OS requires space for shadow copies of the partition.
There appears to be circumstances where the OS writes to the partition not leaving 50 MB of free space. When other users have found themselves in this situation they have problems with Windows imaging.
My System SpecsSystem Spec
08 Oct 2010   #9
Microsoft MVP

W 7 64-bit Ultimate
 
 

Quote   Quote: Originally Posted by mjf View Post



When other users have found themselves in this situation they have problems with Windows imaging.


Then it may be helpful to get them to enlarge the size of the SysResv partition using something like the Partition Wizard boot disk, similar to Step One, then resize the SysResv into the free space created by the OS shrink; have a look at this tutorial for an out-line.

Dual Boot : Create Partitions Using PWBD
My System SpecsSystem Spec
08 Oct 2010   #10
mjf

Windows 7x64 Home Premium SP1
 
 

Quote   Quote: Originally Posted by Bare Foot Kid View Post
Quote   Quote: Originally Posted by mjf View Post



When other users have found themselves in this situation they have problems with Windows imaging.


Then it may be helpful to get them to enlarge the size of the SysResv partition using something like the Partition Wizard boot disk, similar to Step One, then resize the SysResv into the free space created by the OS shrink; have a look at this tutorial for an out-line.

Dual Boot : Create Partitions Using PWBD
Agreed. This is a very useful tutorial. Maybe the partition should have been larger to begin with?
My System SpecsSystem Spec
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