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Windows 7: Benefits of GPT vs MBR Primary and MBR Logical Partitions ?

28 Dec 2014   #51
mjf

Windows 7x64 Home Premium SP1
 
 

Quote   Quote: Originally Posted by jumanji View Post

@mjf, your statement is confusing. Are you agreeing with Geneo's statement "Windows never rewrites a disk signature" or are you saying that Windows writes the new signature?
Sorry for any confusion.
Yes Windows will write a new disk signature when there is a clash and you need to reassign a new disk signature through an application like Windows Disk Management. I've had external WD drives with the same disk signature and they need to be changed if both are connected. In the MBR disk signatures identify a specific disk (HDD).


My System SpecsSystem Spec
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28 Dec 2014   #52
GeneO

Windows 10 Pro. EFI boot partition, full EFI boot
 
 

Quote   Quote: Originally Posted by mjf View Post
Quote   Quote: Originally Posted by jumanji View Post

@mjf, your statement is confusing. Are you agreeing with Geneo's statement "Windows never rewrites a disk signature" or are you saying that Windows writes the new signature?
Sorry for any confusion.
Yes Windows will write a new disk signature when there is a clash and you need to reassign a new disk signature through an application like Windows Disk Management. I've had external WD drives with the same disk signature and they need to be changed if both are connected. In the MBR disk signatures identify a specific disk (HDD).

But you manually have to resolve the clash by bringing one of the drives online (then windows creates a new signature for it).

I think the reason why WD external drives had such clashes is that they deliver pre-formatted disks ready to use out of the box. They don't format them in windows; they probably had a master that the cloned, including disk signature - so they all had the same signature. I expect that have since fixed that process (they could just use the epoch time- the number of seconds since Jan 1, 1970 for the signature for instance).
My System SpecsSystem Spec
28 Dec 2014   #53
jumanji

Windows 7 Home Premium 32 bit
 
 

@alan10, I would still like to know:

Once you had your OS kicking in - in whatever way you managed to - you could have tried to change the Unique ID of your GPT drive to 00 00 00 00 and your GPT drive should have come alive after a reboot - provided that is the only change that had taken place as you aver.( With Diskpart Uniqueid command one can change the signature of any disk)

Why did you not try it and why did you straightaway go into data recovery mode with Lazesoft?

Since a GPT/MBR mix is being used on your system, atleast now I would advise you to save a copy of the GPT Protective MBR at LBA0 so that you can easily restore it in case of any mishap in future. I have already confirmed that it works in my post#44.

The GPT data redundancy (the backup of the GPT header and partition tables in the last 32 sectors of the GPT drive) do not come to one's rescue if the Protective MBR gets corrupted.
My System SpecsSystem Spec
.

29 Dec 2014   #54
GeneO

Windows 10 Pro. EFI boot partition, full EFI boot
 
 

Hi Jumanji,

I think he would have to have done more than that. If you read the link I posted he tried to reset the GUID for the GPT via diskpart. But diskpart thinks it is a MBR disk, so it did not work. If he would have set it to zero using DISKPART UNIQUEID, it would have just generated a new MBR signature, not GUID, and it still would appear as a MBR disk, though the conflict would have been gone. Setting the GUID to zero with a hex editor or whatever would still have left being interpreted as a MBR disk.

He would have had to change the MBR partition type to 0xEE though and the MBR signature to zero with an editor. Then who knows what else to make it appear as a GPT again.
My System SpecsSystem Spec
29 Dec 2014   #55
jumanji

Windows 7 Home Premium 32 bit
 
 

Ok, that makes sense.

So in the final analysis, do you agree that had he saved the Protective MBR earlier and restored it once the problem cropped up, he would have saved the situation and would have been back in business without calling upon Lazesoft or any other data recovery software?

My little experiment does confirm so. I corrupted the Protective MBR and then restored it from the backup and the drive was back as before.(Also when Windows initialises a disk as an MBR disk, it does not write anything beyond Sector 0. It just writes the MBR Code and zeroes the Partition table area in sector 0, ready to take a new partition table.)
My System SpecsSystem Spec
29 Dec 2014   #56
alan10

Windows 7 Ultimate 64 bit SP1 x64
 
 

Quote:
I think the reason why WD external drives had such clashes is that they deliver pre-formatted disks ready to use out of the box.
Sorry but that is totally and completely wrong.
There was only one off WDC HDD plus one off Samsung HDD.

For some reason Windows 7 woke up stupid - more stupid than normal.
Something idiotic (e.g. Windows 7) decided that as a special action the very first drive to be enumerated would have its GPT style ID replaced with an MBR style ID,
and out of its own latent malicious hostility towards me it did NOT use a purely random 8 digit number,
BUT copied the 8 digit number that belonged to my Samsung HDD,
so that when the Samsung was eventually enumerated it got thrown off-line.

Until 15 hours ago I would not have known what I have been shown in post #44 above,
and so would not have known about the location of 4 bytes that could be set to zero.

Even if I had known I would not have dabbled because I was still very new to the unpredictable nature of Windows 7,
having spend some years adapting to and then taming Windows XP.

Whether editing those bytes would have helped me is too late to know.

The beautiful thing about Data Recovery with Lazesoft is that it does not risk altering the partition which has lost data.
There is NO WAY that I would trust :-
the reliability of any Windows utilities to safely write to a disk without causing accidenetal data loss ;
or my ability to use correctly deploy and employ unfamiliar disk editing tools.

Regards
Alan
My System SpecsSystem Spec
29 Dec 2014   #57
GeneO

Windows 10 Pro. EFI boot partition, full EFI boot
 
 

Quote   Quote: Originally Posted by alan10 View Post
Quote:
I think the reason why WD external drives had such clashes is that they deliver pre-formatted disks ready to use out of the box.
Sorry but that is totally and completely wrong.
There was only one off WDC HDD plus one off Samsung HDD.
Alan, I wasn't talking about your issue with your WDC drive, but the one Michael and others have run across with two WDC having the same disk ID.

Quote:

For some reason Windows 7 woke up stupid - more stupid than normal.
Something idiotic (e.g. Windows 7) decided that as a special action the very first drive to be enumerated would have its GPT style ID replaced with an MBR style ID, and out of its own latent malicious hostility towards me it did NOT use a purely random 8 digit number,
BUT copied the 8 digit number that belonged to my Samsung HDD,
As others have also pointed out, it is more likely something happened in your immediate previous boot or the Syslinux boot that failed immediately in between, since Syslinux was obviously having an issue. If you only use the SysLinux for recovery tools like partition magic and macrium, were you trying to boot to it to fix some problem?
My System SpecsSystem Spec
29 Dec 2014   #58
alan10

Windows 7 Ultimate 64 bit SP1 x64
 
 

I doubt that anyone here believes that Windows ignores disk identities.
If it finds an identity clash it fixes it somehow - typically by putting something off-line.

Does anyone here seriously believe that SysLinux on a Flash drive would go out of its way to fix a HDD problem that it was NOT supposed to address ?

I do not care what I was doing with what bit of SysLinux,
nothing should have "Fixed" my GPT drive which still holds all the original data in perfect condition.
The bulk of that data was Macrium Reflect image backups which are created with extensive hash-checksums too detect ANY CORRUPTION that may occur to the files,
and there is a total of about 300 GB data in such image files ranging in size from 50 MB up to 6000 MB each,
and Lazesoft recovered them all and they have all been checksum validated by Macrium.

Only Windows is so perverse that it sticks its nose in where it does no need to be,
and ONLY WINDOWS would have thought that an EXACT duplicate of the Samsung HDD MBR ID would enhance my WDC HDD GPT

The actual SysLinux components were Grub.exe at 282 kB and Idlinux.sys at 37 kB plus about 6 other sundry files to launch a Linux boot that then gives me a menu to choose from various recovery tools.
Code:
29/01/2013  16:40        44,812,288 PartitionWizard-Pro-7.iso
30/01/2013  12:49       181,530,624 Macrium-Rescue-5529.iso
29/01/2013  16:38        44,756,992 PartitionWizard-Pro-6.iso
19/01/2013  16:43       181,518,336 Macrium-Rescue-5496.iso
You seriously underestimate my capabilities by rashly assuming I was fixing something with SysLinux.
I was actually testing how to boot into my new Flash Drive with the YUMI Boot loader and ENSURE that both the latest and the previous Boot Rescue versions of PartitionWizard and Macrium-Rescue could be launched should I ever have need of them.

I WAS NOT FIXING ANYTHING,
I WAS SIMPLY TESTING TO BE SURE THAT IF / WHEN I NEEDED THE TOOL IT WOULD WORK FOR ME.

Anyone who creates partition image backups and does not test them until a moment of need is living in a fool's paradise.

THIS is the current site of the YUMI Boot Loader
YUMI
The current version is
YUMI-2.0.1.2.exe December 12, 2014 Changelog

‎The version which I was using was much simpler, and dated
02 ‎October ‎2012, ‏‎09:05:26

I think it is foolish for anyone to suggest that the Yumi boot loader would use its Linux capabilities to fix a problem that it was not asked to fix.
There really was no problem, until Windows chose to trash a Disk that had no problem and still holds all the files in good condition.

Geneo, you were very naive when you said
"The ppl that wrote this code are not stupid."
They are so stupid that in my first year of using Windows 7, it trashed itself with two separate "Windows Updates".
I NEVER allow an update until I have made a backup - but originally the differences from XP were so different that I had not completely blocked the updates and I lost work in progress as my PC was turned into dead metal, i.e. non-boot-able.
Fortunately my Boot Recovery tools were able to rescue all my "lost work-in-progress" before I restored my previous image backup.

Others MAY have suggested that SysLinux might have been implicated in my GPT disaster
But you are the only one who continues to drone on-and-on about this,
and you totally ignore the peculiar 4 billion to one "random" coincidence that resulted in the WDC drive being given the same ID as the Samsung Drive.
Please give up what seem to be needless repetitions of your beliefs that Windows is perfect and does no harm - that is not my experience.

Regards
Alan
My System SpecsSystem Spec
29 Dec 2014   #59
GeneO

Windows 10 Pro. EFI boot partition, full EFI boot
 
 

Well I give up all right, but not for any of your reasons.
My System SpecsSystem Spec
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 Benefits of GPT vs MBR Primary and MBR Logical Partitions ?




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