Removing Microsoft Reserved Partition (MSR) from secondary GPT disk?

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theta

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Oct 4, 2009
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I've been searching around to figure out the exact purpose of the MSR, and have found frustratingly little information on what exactly it does. Microsoft considers it a vital partition, but I'm unclear on why. So basically I want to know: if I remove the MSR from a non-boot disk, will it render the rest of the partition unreadable in Windows?

If it turns out that it just provides extra functionality for Windows, but that I can still access my data on a drive without it (which seems to me the likeliest scenario, since otherwise it would appear that all disks that weren't partitioned on Windows are unreadable on Windows!), then I'd prefer to remove it. I run Linux nearly full-time and boot into Windows only a few times a month--Windows exists on my main boot drive where I plan to keep the MSR intact. I'd just like to remove unnecessary partitions from my secondary disks.
 

RealBeast

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For Windows 7/8 it is usually essential (if the OS was installed using the SRP), although the one that you see on a secondary drive may not be the only one -- and the one that is actually working may be on the boot drive. One good reason to do a clean install with only one drive attached is so that you know the SRP is on the boot drive.

It contains the bootloader and if you do not have a functioning SRP, Win 7/8 will not run if the install was initially done with an SRP. It is possible to do an install and not have an SRP, but you cannot delete the active SRP after an install is done. Take a look at THIS for more information on this topic.

If you delete it from the non-OS drive and find that you cannot boot, just insert the install disk and you can repair the SRP and place it on the boot drive.
 

RealBeast

Titan
Moderator
For Windows 7/8 it is usually essential (if the OS was installed using the SRP), although the one that you see on a secondary drive may not be the only one -- and the one that is actually working may be on the boot drive. One good reason to do a clean install with only one drive attached is so that you know the SRP is on the boot drive.

It contains the bootloader and if you do not have a functioning SRP, Win 7/8 will not run if the install was initially done with an SRP. It is possible to do an install and not have an SRP, but you cannot delete the active SRP after an install is done. Take a look at THIS for more information on this topic.

If you delete it from the non-OS drive and find that you cannot boot, just insert the install disk and you can repair the SRP and place it on the boot drive.
 

Paul Mullen

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Sep 21, 2013
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Boot files (including NTLDR, boot manager and the BCD data) are in the EFI System Partition (ESP). The MSR (Microsoft Reserved) partition is simply 128 MB of empty space reserved by Microsoft because they wanted to leave room to convert a basic partition to a dynamic partition in future and the UEFI partition specification does not permit gaps between partitions.

Microsoft say the MSR is required on a GPT bootable drive but not needed on a secondary data drive. However the Windows Disk Manager seems to always create ESP and MSR partitions just in case you make the drive bootable in future. It should be safe to delete them provided that you can expand the data partition so that there is no gap.
If you do leave a gap your partitions will not be compliant with the UEFI standard and It is possible that some disk utilities may see the gap as the end of useful data, and then decide to overwrite any partitions after the gap!
 
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