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jonah8208

Drive Converion Question

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Just a quick question re converting MBR drive to GPT. I have all my media cloned onto a new 3GB hdd. Realising I should have initialised it as GPT, if I now use Acronis to do a convert to GPT from MBR am I going to lose all my sharing permissions and have to configure it all from scratch. Anyone done this before? Jonah

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17 hours ago, jonah8208 said:

Just a quick question re converting MBR drive to GPT. I have all my media cloned onto a new 3GB hdd. Realising I should have initialised it as GPT, if I now use Acronis to do a convert to GPT from MBR am I going to lose all my sharing permissions and have to configure it all from scratch. Anyone done this before? Jonah

Converting a drive from MBR to GPT only affects the partitioning type, no changes are made to the filesystems, so there are no issues foreseeable,

Whether "Acronis" will do a plain conversion (which is all that is needed) or - due to its "automagical" nature introduce any change, it's hard to say.

The only reason why there could be changes to the last partition/filesystem would be if there is not enough space at the end of the disk for the reversed copy of the GPT tables, but it is extremely rare that a "normally" partitioned MBR disk is occupying the whole disk.

At the beginning there are no issues, usually the whole stuff goes in 32 sectors, so even the "old" 63 sectors before were enough, and with the "new" default of 2048 there are definitely no issues.

A quick check with gdisk would be a good idea anyway:

https://www.rodsbooks.com/gdisk/

which can also do a "manual" conversion.

jaclaz

Edited by jaclaz
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There may be booting issues if converting a bootable MBR drive to GPT. Check if your motherboard and OS support EFI boot. Converting data storage drive is much safer. The full backup is highly recommended in any case.

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@Yellow Horror

Not that I am suggesting these workarounds as a "standard", but JFYI, it is perfectly possible to boot a GPT disk from BIOS (of course provided that the OS understands GPT disks) with a few tricks (and without making a Hybrid-MBR disk):

http://reboot.pro/topic/19516-hack-bootmgr-to-boot-windows-in-bios-to-gpt/

(don't be fooled by the title, several different approaches are used, none of which actually modifies the BOOTMGR)

of course only useful in some "edge" or very "specific" cases.

Simplest being using the grub4dos UMBR:

http://reboot.pro/topic/19516-hack-bootmgr-to-boot-windows-in-bios-to-gpt/?p=197690

but several other possibilities/variations have been experimented successfully.

jaclaz

 

Edited by jaclaz
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For the record - When I initially cloned my original 1Tb drive onto my new 3Tb using Acronis Disk Partition 12 set to do a straight non bootable clone - it worked - sort of - but I could not boot off my SSD (C) Drive where the OS sits. To fix this I had to do a "repair boot sector" after booting from a Windows 10 Image. This gave me a 2TB data drive with 762Gb unallocated (because I forgot to initialise the drive as GPT). I used Acronis again to fix this without losing all the data I had just cloned across to the new drive. Acronis converted my non bootable 3Tb Data Store from MBR to GPT with zero issues and I was then able to merge the unallocated 762Gb onto the drive as originally intended. So Acronis works as advertised provided you read the instructions first! Thanks for the Hacks jaclaz I will have a play with them on a test box I was considering a hybrid for a laptop that needs loads of storage but has only one HDD slot and cannot use cloud drives or NAS at work - interesting, and even better its not my project so I can shrug and walk away if it all goes wrong.

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Sure, this is perfectly normal.

The BIOS/MBR partitioning scheme has a limit in 2^32-1 sectors, i.e. roughly 2.2 TiB if sectors are 512 bytes in size.

At least starting from Windows 7, it is possible to access (as a separate volume) the 726 Gb nonetheless, again using a trick or two, bit MS won't allow to create such an "out of faked specs" setup, JFYI (start from around here):

 

But the non-bootability probably comes from another issue, the BIOS/MBR booting sequence is normally:

BIOS->MBR->PBR of active partition->BOOTMGR->\boot\BCD->WINLOAD.EXE

the UEFI/GPT is completely different:

UEFI->EFI bootloader on EFI "reserved" partition (possibly BOOTX64.EFI or BOOTIA32.EFI or anything else registered in the NVRAM)->\efi\microsoft\boot\BCD->WINLOAD.EFI

jaclaz

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37 minutes ago, jonah8208 said:

I was considering a hybrid for a laptop that needs loads of storage but has only one HDD slot

If it have DVD drive and you don't need it, you may replace it with a HDD/SSD drive. Search for "HDD caddy" for additional info.

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14 hours ago, cdob said:

In addition, there is integrated tool nowadays: MBR2GPT
https://docs.microsoft.com/en-gb/windows/deployment/mbr-to-gpt
 

Which has (rightly or wrongly) a number of checks/limitations (that gdisk hasn't AFAICT).

Quote

Before any change to the disk is made, MBR2GPT validates the layout and geometry of the selected disk to ensure that:+

The disk is currently using MBR

There is enough space not occupied by partitions to store the primary and secondary GPTs:

16KB + 2 sectors at the front of the disk

16KB + 1 sector at the end of the disk

There are at most 3 primary partitions in the MBR partition table

One of the partitions is set as active and is the system partition

The disk does not have any extended/logical partition

The BCD store on the system partition contains a default OS entry pointing to an OS partition

The volume IDs can be retrieved for each volume which has a drive letter assigned

All partitions on the disk are of MBR types recognized by Windows or has a mapping specified using the /map command-line option

If any of these checks fails, the conversion will not proceed and an error will be returned.

Some make sense, some not-so-much, particularly it seems dumb to exclude the conversion of non-system disks and to limit the conversion to partitions that are recognized by windows,

jaclaz

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On 02/01/2018 at 7:44 PM, Yellow Horror said:

If it have DVD drive and you don't need it, you may replace it with a HDD/SSD drive. Search for "HDD caddy" for additional info.

It has no DVD Drive just an empty slot behind the case, it does have the data connection on the Mobo so I could look at that - thanks man never occurred to me to use the DVD slot.

 

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1 hour ago, jonah8208 said:

It has no DVD Drive just an empty slot behind the case, it does have the data connection on the Mobo so I could look at that - thanks man never occurred to me to use the DVD slot.

 

Just in case, and probably unneeded:

jaclaz

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