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

[IcarusII]

Hi,

Just read a tutorial on here about optimising hdd performance in w7. 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

 

[whs]

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 Win7 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.

 

[IcarusII]

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

Cheers

 

[Bare Foot Kid]

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

 

[mjf]

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.

 

[Bare Foot Kid]

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

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[gregrocker]

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.

 

[mjf]

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.

 

[Bare Foot Kid]

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

 

[mjf]

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?

 

[Bare Foot Kid]

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?

Remember, MS originally set the size at 200MB and there was such a backlash that the size was reduced to the current 100MB?

 

[IcarusII]

Hi folks,

Sorry to chip in here during your discussion. Early on in the thread i thought i understood why the 100mb boot partition exists. However the more you learned folk discuss the details the more lost I've become. I'm a real noob here and so I'll ask two questions, the first of which will reveal how little I know:
A) on a brand new hdd, and a clean install of w7 will windows automatically create this 100mb boot partition?
B) is there a tutorial or wiki somewhere where I can read up on the standard structure of a windows install? Infer totally lost with primary, active, sys reserved, normal partitions etc. I really could do with understanding this once and for all so I am not guessing!

Many thanks
Matt

 

[whs]

ad A) depends. If you install into a predefined partition, it will not create the 100MBs. If you install on a blank disk, it may depending whether it is a retail version or an OEM version.

ad B) I am sure there are many tutorials. You could just Google it. Here is an example that explains the NTFS partition structure: NTFS Architecture Overview Else there is always Wikipedia: Disk partitioning - Wikipedia, the free encyclopedia

 

[IcarusII]

Thanks very much for the info and the links. Very informative - especially the PC Guide info on ntfs architecture. Much appreciated. After reading that lot and now also having googles about the 100 mb boot partition (i didn't realise only w7 adds this toba clean install) I have a final architecture question:

A user in these forums stated that recent ms os' don't need to be in a primary partition to work. He said he was running pre release w7 from a logical drive in his extended partition

This contradicts everything I've read because to boot that os in that logical drive you need to make the drive active right? And you aren't allowed to make logical partitions active - so help? What he doing?

Matt

 

[Bare Foot Kid]

Hello Matt.



As long as there is another Windows Operating System (OS) booting from a primary partition, a second (or third) can be run from an extended/logical partition, they will share the files needed to boot; that is part of the reason (among several others) for the introduction of the SysResv partition, so all the boot files can be stored in one central location.

A Windows OS cannot boot independently from an extended/logical partition.



I hope this helps clear it up for you.

 

[mjf]

Thanks very much for the info and the links. Very informative - especially the PC Guide info on ntfs architecture. Much appreciated. After reading that lot and now also having googles about the 100 mb boot partition (i didn't realise only w7 adds this toba clean install) I have a final architecture question:

A user in these forums stated that recent ms os' don't need to be in a primary partition to work. He said he was running pre release w7 from a logical drive in his extended partition

This contradicts everything I've read because to boot that os in that logical drive you need to make the drive active right? And you aren't allowed to make logical partitions active - so help? What he doing?

Matt

Here's a reference to the Master Boot Record, not to be confused with the Volume Boot Record (which is partition based).
Master boot record - Wikipedia, the free encyclopedia
The MBR is where the BIOS firmware goes to hand over it's role in the boot sequence. In the MBR is the partition table with one partition location flagged or marked active. This is often the little 100MB partition we've been talking about.