2TB MBR partition limit - help me understand

[VirtualLarry]

http://www.servethehome.com/?p=231#more-231
" One thing I had forgotten is that WHS is built on Windows Server 2003 and can only utilize MBR partitions. While this is generally fine, the 11x 1.5TB drives - 2x for parity and -1x for a hotspare yielded 10.92TB of available storage (1.365TB x 8). Due to the MBR partition and WHS limitations one can have a maximum of 8TB in a raid array for WHS on a set of drives. This is because 2TB per MBR partition and 4 partitions per device. "

Is this true? I thought that the 2TB limit was a hard limit, in that you could only use 2TB of the physical drive for a partition, not that you could partition MULTIPLE 2TB partitions on a larger physical disk.

Can someone comment which is correct?

According to this:
http://en.wikipedia.org/wiki/Master_boot_record
"Both the partition length and partition start address are stored as 32-bit quantities. Because the block size is 512 bytes, this implies that neither the maximum size of a partition nor the maximum start address (both in bytes) can exceed 2^32 × 512 bytes, or 2 TiB."

That was my understanding, that any sectors above a 2TB limit were entirely off-limits to MBR partitions.

 

[IndyColtsFan]

http://www.servethehome.com/?p=231#more-231
" One thing I had forgotten is that WHS is built on Windows Server 2003 and can only utilize MBR partitions. While this is generally fine, the 11x 1.5TB drives - 2x for parity and -1x for a hotspare yielded 10.92TB of available storage (1.365TB x 8). Due to the MBR partition and WHS limitations one can have a maximum of 8TB in a raid array for WHS on a set of drives. This is because 2TB per MBR partition and 4 partitions per device. "

Is this true? I thought that the 2TB limit was a hard limit, in that you could only use 2TB of the physical drive for a partition, not that you could partition MULTIPLE 2TB partitions on a larger physical disk.

Can someone comment which is correct?

According to this:
http://en.wikipedia.org/wiki/Master_boot_record
"Both the partition length and partition start address are stored as 32-bit quantities. Because the block size is 512 bytes, this implies that neither the maximum size of a partition nor the maximum start address (both in bytes) can exceed 2^32 × 512 bytes, or 2 TiB."

That was my understanding, that any sectors above a 2TB limit were entirely off-limits to MBR partitions.

I thought the same as you, that 2 TB was addressable limit on a single physical disk using MBR. To my knowledge, 2 TB is the max volume size (using MBR) in Windows 2003. To get around this, you have to use GPT disks. I am not sure if WHS can use GPT; if it can, that would be one way around the limit.

 

[RebateMonger]

Microsoft Windows and GPT FAQ
http://www.microsoft.com/whdc/device/storage/GPT_FAQ.mspx

"The maximum partition (and disk) size is a function of the operating system version. Windows XP and the original release of Windows Server 2003 have a limit of 2TB per physical disk, including all partitions." <----This means that under MBR, the maximum usable disk size is 2 TB per physical disk.

I thought I'd read of folks using GPT partitions to create a large RAID 5 partition underneath WHS. This would have to be for an added data "disk", since Server 2003 can't boot to a GPT partition except on an Itanium-based system.

Edit:
This reminds me: Anybody know when the first 2TB+ disks will be released (and what size they'll be)? I imagine those disks will create quite a stir, in Windows, at least, because of the need for GPT and the general inability to boot to GPT with today's standard hardware setup.

"Dr Geoff Barrall, founder and CEO of Drobo gave out his opinion in London last week that there should be a 3TB drive for Drobos by April next year. He didn't name the supplier, but Drobo does use Western Digital drives, so this 3TB drive could be a black one."

Remember when disks larger than 137 GB often included a free disk controller in the box? I don't know what the early solution is going to be for this new disk challenge.

A couple of months ago, I asked an MS Tech person if Microsoft had any magical plans to ease the transition, but he didn't have any magic to share.

 

[yinan]

This doesnt seem like it will be a problem with the modern versions of Windows.

 

[RebateMonger]

This doesnt seem like it will be a problem with the modern versions of Windows.

Some potential GPT problems with Vista and Win7:

1) You need an EFI-capable motherboard to boot from a GPT disk. Otherwise, you'll need to boot from a 2 TB or smaller MBR disk and use larger disks as secondary disks.

Traditional BIOS-based booting won't work. I don't know much about the EFI capability of recent motherboards, but assuming that your non-Intel motherboard supports EFI may not be a good assumption.

2) If you need to scan a "large" disk for errors, you'll find that your PC may be unusable for days. But this is the case with any "large" disk, MBR or GPT.

3) Current backup, data recovery, and disk utility programs may have issues with GPT disks.

 

[VirtualLarry]

We need MBR-X. A boot record layout, that supports 64-bit LBA start and size fields, and does away with the CHS fields. I'm sure someone smart could design one. It would screw with disk utilities until they were updated, but it wouldn't be hard to release BIOS updates to support it for existing mobos, and MS could add some code to their OSes to process it too.

 

[Tsaico]

I agree with everything will scale fine. With 64-bit addressing becoming more and more standard, I don't think as a home user, you will come across too many problems from a usage side. But I agree with Rebatemonger, if you run into any operations problems, you might a well just junk the disk and start over, scanning will take forever.

For myself, I limit myself to 500 GB drives for this reason. I also do not carry a USB stick over 2 GB, and the one I use for day to day is 512MB. Primarily it forces me into keeping things tidy and not just clutter up the driver, somwhat limiting my data loss when I run the thing through the washer, drop it whatever.
Until single file sizes that are multiple gigs a piece become commmon place, I don't see the need for huge single partitions. Especially with cloud computing and clustering becoming cheaper in the datawarehouses, and really the only thing I need for large single partitions is to hold my "backed up" DVD collection which I don't really watch, just thought I should have it "online" at all times.

 

[Nothinman]

We need MBR-X. A boot record layout, that supports 64-bit LBA start and size fields, and does away with the CHS fields. I'm sure someone smart could design one. It would screw with disk utilities until they were updated, but it wouldn't be hard to release BIOS updates to support it for existing mobos, and MS could add some code to their OSes to process it too.

No, we just need BIOS updates to support GTP. Adding yet another partitioning method would just make the situation worse.

For myself, I limit myself to 500 GB drives for this reason. I also do not carry a USB stick over 2 GB, and the one I use for day to day is 512MB.

I'd go mad with retarded limitations like that. The computer is supposed to work for me, not vice versa.

 

[VirtualLarry]

No, we just need BIOS updates to support GTP. Adding yet another partitioning method would just make the situation worse.

I'd go mad with retarded limitations like that. The computer is supposed to work for me, not vice versa.

But doesn't supporting GPT require supporting EFI? Or is that not true. If there's a way to support GPT booting from normal BIOS, without EFI, then I'm all for it. But if it requires EFI, then I propose an alternative interim standard, just to get things working again.

 

[Nothinman]

But doesn't supporting GPT require supporting EFI? Or is that not true. If there's a way to support GPT booting from normal BIOS, without EFI, then I'm all for it. But if it requires EFI, then I propose an alternative interim standard, just to get things working again.

EFI is just a type of firmware, AFAIK there's nothing technically tying GPT to it. But even if there is, getting everyone over to EFI would be infinitely better than some duct tape solution like you propose.

 

[RebateMonger]

I imagine we'll be hearing a LOT more about EFI once 2 GB+ disks are released. Macintosh folks have and advantage here, since Macs have been working with EFI for quite a while.

I've looked for details of "real-life" experience with PCs and EFI. This discussion
http://vip.asus.com/forum/view.aspx...d_id=1&model=P5Q&#37;20Deluxe&page=1&count=57
from late 2009 is interesting. Asus had just released an EFI flash for the Asus P5Q Deluxe motherboard. Initial reports mentioned that memory remap was broken and there was no overclocking capability offered.

I hope I'm wrong, but I get the feeling that EFI support for many of us is going to come with a new motherboard.

 

[Nothinman]

I imagine we'll be hearing a LOT more about EFI once 2 GB+ disks are released. Macintosh folks have and advantage here, since Macs have been working with EFI for quite a while.

I've looked for details of "real-life" experience with PCs and EFI. This discussion
http://vip.asus.com/forum/view.aspx...8&board_id=1&model=P5Q Deluxe&page=1&count=57
from late 2009 is interesting. Asus had just released an EFI flash for the Asus P5Q Deluxe motherboard. Initial reports mentioned that memory remap was broken and there was no overclocking capability offered.

I hope I'm wrong, but I get the feeling that EFI support for many of us is going to come with a new motherboard.

Macs are PCs =)

I'd probably say you're right about EFI based firmware being written for existing motherboard simply because the manufacturers are lazy and won't want to support every older device.

But really, GPT support in firmware is only needed for booting so as long as people have a <2TB drive for the OS it won't matter.

 

[RebateMonger]

But really, GPT support in firmware is only needed for booting so as long as people have a <2TB drive for the OS it won't matter.

Yeah. It's quite possible we'll end up with a common "high-end PC" configuration of a small SSD for a boot disk and a 3 TB+ data disk. Then if MS can modify Windows a bit so that the OS disk is write-locked (except when intentionally installing certified programs), we might not have as big a malware problem. And it'll look a bit more like George Orwell's 1984.

 

[Nothinman]

Yeah. It's quite possible we'll end up with a common "high-end PC" configuration of a small SSD for a boot disk and a 3 TB+ data disk. Then if MS can modify Windows a bit so that the OS disk is write-locked (except when intentionally installing certified programs), we might not have as big a malware problem. And it'll look a bit more like George Orwell's 1984.

MS should also consider trimming Windows down, people are already complaining about trying to squeeze Win7 on a 32G SSD. And UAC causes enough problems for people as is, restricting things even more would just piss people off more. Something like SteadyState might work, but I've never touched it so I have no idea how well it works.

I'm just glad none of this applies to me, I can configure all of my Linux systems any way my mind can imagine. =)