GPT -GUID Partition Table- Disks, some basic questions

NTDEV
1

I have been trying to find up-to-date information about how Windows manage GPT (GUID Partition Disks).

I have found some pretty decent info but not very up-to-date and somewhat contradictory.

So I wonder whether the topic has been updated since that documents have been published.

My basic questions about this subject are the following:

  1. Is it possible to have a bootable GPT disk with anything other than Itanium Windows version ?

  2. Theoretically it is possible to boot on GPT under Vista/Server 2008 for EFI based systems. Right?

  3. I recall there was something called Dynamic Disks from MS. Was it the same as GPT? If not, where is it documented ?

Inaki.

2

>3. I recall there was something called Dynamic Disks from MS. Was it the same

as GPT? If not, where is it documented ?

No. Not at all.

Starting from w2k, Windows contains the simplified licensed version of
Veritas’s VxVM (aka Storage Foundation). This is a software-based RAID, and is
called Dynamic Disk.

GPT support started from Server 2003. I don’t remember whether you can boot
from GPT on non-EFI machine, but non-boot disks can surely be GPT for Server
2003.

GPT and Dynamic Disk have nothing in common in their on-disk structures.

So, you have 3 different on-disk partition table layouts - MBR, GPT and Dynamic
Disk.

–
Maxim Shatskih, Windows DDK MVP
StorageCraft Corporation
xxxxx@storagecraft.com
http://www.storagecraft.com

3

Not quite correct.

Dynamic or LDM disks are not a disk format type like MBR or GPT. Instead
a dynamic disk can be either MBR format or GPT format disk. The term
“dynamic disk” is a misnomer, it is simply a partition type - 0x42 for
MBR disks and PARTITION_LDM_METADATA_GUID and PARTITION_LDM_DATA_GUID
for GPT disks. For MBR format disks dynamic disks hide their metadata at
the end of the disk in a hidden secret partition that does not show up
in the partition table. For GPT disks the metadata is in the
PARTITION_LDM_METADATA_GUID and the “dynamic disk” is the
PARTITION_LDM_DATA_GUID partition.

-----Original Message-----
From: xxxxx@lists.osr.com
[mailto:xxxxx@lists.osr.com] On Behalf Of Maxim S. Shatskih
Sent: Monday, October 15, 2007 3:41 PM
To: Windows System Software Devs Interest List
Subject: Re:[ntdev] GPT -GUID Partition Table- Disks, some basic
questions

  1. I recall there was something called Dynamic Disks from MS. Was it
    the same
    as GPT? If not, where is it documented ?

No. Not at all.

Starting from w2k, Windows contains the simplified licensed version of
Veritas’s VxVM (aka Storage Foundation). This is a software-based RAID,
and is
called Dynamic Disk.

GPT support started from Server 2003. I don’t remember whether you can
boot
from GPT on non-EFI machine, but non-boot disks can surely be GPT for
Server
2003.

GPT and Dynamic Disk have nothing in common in their on-disk structures.

So, you have 3 different on-disk partition table layouts - MBR, GPT and
Dynamic
Disk.

–
Maxim Shatskih, Windows DDK MVP
StorageCraft Corporation
xxxxx@storagecraft.com
http://www.storagecraft.com

NTDEV is sponsored by OSR

For our schedule of WDF, WDM, debugging and other seminars visit:
http://www.osr.com/seminars

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http://www.osronline.com/page.cfm?name=ListServer

4

Thanks for correction, I never saw Dynamic GPT disks before and didn’t know
that they are possible.

GPT disk itself has an MBR partition table of 1 entry of some special type
(0xee or such) describing the whole disk.

LDM metadata for an MBR Dynamic Disk are at sector 6 and so on of the
physical disk, starts with “PRIVHEAD” string. It (at least its root) is not at
the end of the disk.

–
Maxim Shatskih, Windows DDK MVP
StorageCraft Corporation
xxxxx@storagecraft.com
http://www.storagecraft.com

“Roddy, Mark” wrote in message news:xxxxx@ntdev…
Not quite correct.

Dynamic or LDM disks are not a disk format type like MBR or GPT. Instead
a dynamic disk can be either MBR format or GPT format disk. The term
“dynamic disk” is a misnomer, it is simply a partition type - 0x42 for
MBR disks and PARTITION_LDM_METADATA_GUID and PARTITION_LDM_DATA_GUID
for GPT disks. For MBR format disks dynamic disks hide their metadata at
the end of the disk in a hidden secret partition that does not show up
in the partition table. For GPT disks the metadata is in the
PARTITION_LDM_METADATA_GUID and the “dynamic disk” is the
PARTITION_LDM_DATA_GUID partition.

-----Original Message-----
From: xxxxx@lists.osr.com
[mailto:xxxxx@lists.osr.com] On Behalf Of Maxim S. Shatskih
Sent: Monday, October 15, 2007 3:41 PM
To: Windows System Software Devs Interest List
Subject: Re:[ntdev] GPT -GUID Partition Table- Disks, some basic
questions

>3. I recall there was something called Dynamic Disks from MS. Was it
the same
>as GPT? If not, where is it documented ?

No. Not at all.

Starting from w2k, Windows contains the simplified licensed version of
Veritas’s VxVM (aka Storage Foundation). This is a software-based RAID,
and is
called Dynamic Disk.

GPT support started from Server 2003. I don’t remember whether you can
boot
from GPT on non-EFI machine, but non-boot disks can surely be GPT for
Server
2003.

GPT and Dynamic Disk have nothing in common in their on-disk structures.

So, you have 3 different on-disk partition table layouts - MBR, GPT and
Dynamic
Disk.

–
Maxim Shatskih, Windows DDK MVP
StorageCraft Corporation
xxxxx@storagecraft.com
http://www.storagecraft.com

—
NTDEV is sponsored by OSR

For our schedule of WDF, WDM, debugging and other seminars visit:
http://www.osr.com/seminars

To unsubscribe, visit the List Server section of OSR Online at
http://www.osronline.com/page.cfm?name=ListServer