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Storage Partitioning: The Issues With MBR

Say Goodbye To Your BIOS: Hello, UEFI!
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Windows setup automatically selects GPT for volumes larger than 2TB and allows users to decide between MBR and GPT for capacities under 2TB. This also applies to the disk management utility if you manage drive volumes on an existing Windows installation. Many BIOSes available today support GPT, but a system without UEFI support wouldn’t be capable of booting an operating system from a GPT partition once it is larger than 2TB. Let’s look at what happens if you go with the conventional MBR.

If UEFI support is unavailable, Windows will still automatically use GPT for drives 2TB or larger and offer the choice between GPT and MBR. All unused capacity above 2TB will not be used (and remain useless if partitioned with MBR).

Windows Vista is clear on this.

You would think that it should be possible to create an additional partition once a 2TB volume has been installed on a drive with 2TB or more of capacity. This is not possible, as MBR limits the entire drive to one partition of up to 2TB. The remaining storage space is now useless. Hence, it is important to only use GPT for large capacity drives, as you won’t face the 2TB limit.

So let’s move on and create a large partition using the GPT layout and the LaCie 4big Quadra eSATA drive.

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Top Comments
  • 14 Hide
    Anonymous , December 30, 2009 6:37 AM
    Excellent article, I've been musing about this myself but never got around to reading up on it. Shame to get official confirmation that motherboard makers are so far behind though.

    The current BIOS really needs to be done away with.

    Much like PATA, Serial and Parallel ports, PCI slots, Floppy connectors, PS/2 connectors, FireWire or the other odds and ends of legacy hardware interfaces that we still pay to have added into modern systems.
  • 14 Hide
    ta152h , December 30, 2009 6:00 AM
    Oh boy, you missed the mark on the PS/2.

    It was released in 1987, and IBM never liked the term MCA, but in any event, it was for Microchannel Architecture.

    However, not all PS/2s were Microchannel. The numbers below 50 were all AT or PC bus machines.

    I don't know what it had to do with BIOS clones. It was a different hardware slot, and prevented cloning of bus architecture, because IBM had many patents on the underlying technology. Of course, they eventually made companies pay for even AT-Bus (often incorrectly referred to as ISA) machines, when their patents were accepted. There was really no reason to worry about BIOS cloning, since other companies were succesful already in getting compatibles without directly copying the underlying BIOS (although, none of them had BASIC built into ROM, but then, who ever used that anyway?).

    It did greatly simplify installing new hardware. Instead of the obnoxious playing with jumpers and switches to find unused IRQs and memory spaces, you'd get a reference disk with the device and you'd run it. That was it. It doesn't sound like much now in the land of plug and play, but it was a HUGE improvement.

    Microchannel also wasn't purely 32-bit. The PS/2 50 and 60 were both 16-bit machines. Of the initially released machines (Model 30, 50, 60, and 80), only the Model 80 had 32-bit slots.

    PS/2s were probably the best made PCs, at least the Microchannel models. They would smash the lousy Lian Li cases (which represent high end now) like they were made of paper. The desktop versions had no cables in them, and could be taken apart in five minutes without any tools. They were extremely reliable as well. Of course, they were expensive as Hell. If memory serves me corretly, the PS/2 Model 50 costed $3598 in 1987, and that was the cheapest Microchannel machine released. It had a really, really slow hard disk too, which always made me laugh. They finally got rid of it (on the 50z) because it got so many complaints, only for it to migrate to the Model 30. Why they thought they needed to keep making this albatross was always funny to me, but they did. It was just soooooo slow.
  • 11 Hide
    ready4dis , December 30, 2009 1:21 PM
    Seriously, the biggest drawback of the standard bios is that it's 16-bit real mode, as opposed to 32-bit protected mode. There is no reason to go away from the BIOS as we know it, keep it simple and as a trampoline to booting your OS, but leave the OS in 32-bit mode, and have all bios interrupts 32-bit. This would give all the same benefits of UEFI without the dramatic change, and would actually simplify a lot of OS code as well. I do OS development in my spare time, and the way current bios' work leaves much to be desired. While UEFI would fix a few of these problems, so would simply making smaller changes to the current bios model.

    For those of you wondering what the benefits of EUFI are over a standard bios here is a quick example. You want to reinstall an OS on your computer, but don't have a driver disk. Well, without your NIC drivers, you can't access the internet to download them. Simple, use another PC and burn it to a CD or thumb drive, and copy them over. Well, with EUFI having network card drivers built into the BIOS, the OS will never be without. You can easily get online and save the hassle's of missing drivers. Sure you will want to update them with windows or linux specific drivers, etc, but at least all hardware will be accessible on the first load of your OS. Their has been a lot more room set aside for EUFI, which means it can have a much nicer interface. Once things get matured, you will see full graphical BIOS menu's, with mouse support and all (point n click). Another benefit would be multi-booting. Rather than using windows' or on of Linuxs' boot managers, EFI would handle all of it for you (it'd be up to the specific MB/bios manufacturer on exactly how it works), but you would no longer have to worry about which OS is compatible with what other OS for multi-booting, it would all be handled by EUFI.

    Ok, well, all that said, I still don't agree with it being as overly complex as it is, but I do agree with a few of the concepts it is (has been?) trying to introduce. The MBR is old, and should have been replaced a long time ago. The 2TB limit is not due to any bios compatibility problems, the bios can load a drive > 2TB no issues. The limit is due to the fact that windows is using an MBR which has the limit of 2TB. There are plenty of OS's booting > 2TB drives using a standard BIOS, so the biggest part about this article, being able to boot > 2TB drives, has no point whatsoever because it's a limit of the operating system, not the bios. If you use a GPT rather than MBR, as long as the OS supported it, you can have > 2TB support with whatever BIOS you're currently using (as long as the bios supported large drives). All current bios' have a 48-bit addressing mode for hard drives, which gives you 144 petabyte limit.
Other Comments
  • -9 Hide
    WheelsOfConfusion , December 30, 2009 5:41 AM
    I don't trust that LaCie enclosure not to cut off the life support to my hibernation pod or try to sever my EV suit's umbilical.
  • 3 Hide
    haplo602 , December 30, 2009 5:50 AM
    have been using EFI on various HP model itanium servers. it is quite nice what it can do. however it needs major modifications for desktop use (a friendly GUI for a start).
  • 2 Hide
    BartG , December 30, 2009 5:56 AM
    mmm, not sure I understand, why dont they just revise the current BIOS so it illuminates some of the limitations and have the benefit of not replacing something that has worked for 25 years...

    Surely there are people in the world smart enough to do that.
  • 14 Hide
    ta152h , December 30, 2009 6:00 AM
    Oh boy, you missed the mark on the PS/2.

    It was released in 1987, and IBM never liked the term MCA, but in any event, it was for Microchannel Architecture.

    However, not all PS/2s were Microchannel. The numbers below 50 were all AT or PC bus machines.

    I don't know what it had to do with BIOS clones. It was a different hardware slot, and prevented cloning of bus architecture, because IBM had many patents on the underlying technology. Of course, they eventually made companies pay for even AT-Bus (often incorrectly referred to as ISA) machines, when their patents were accepted. There was really no reason to worry about BIOS cloning, since other companies were succesful already in getting compatibles without directly copying the underlying BIOS (although, none of them had BASIC built into ROM, but then, who ever used that anyway?).

    It did greatly simplify installing new hardware. Instead of the obnoxious playing with jumpers and switches to find unused IRQs and memory spaces, you'd get a reference disk with the device and you'd run it. That was it. It doesn't sound like much now in the land of plug and play, but it was a HUGE improvement.

    Microchannel also wasn't purely 32-bit. The PS/2 50 and 60 were both 16-bit machines. Of the initially released machines (Model 30, 50, 60, and 80), only the Model 80 had 32-bit slots.

    PS/2s were probably the best made PCs, at least the Microchannel models. They would smash the lousy Lian Li cases (which represent high end now) like they were made of paper. The desktop versions had no cables in them, and could be taken apart in five minutes without any tools. They were extremely reliable as well. Of course, they were expensive as Hell. If memory serves me corretly, the PS/2 Model 50 costed $3598 in 1987, and that was the cheapest Microchannel machine released. It had a really, really slow hard disk too, which always made me laugh. They finally got rid of it (on the 50z) because it got so many complaints, only for it to migrate to the Model 30. Why they thought they needed to keep making this albatross was always funny to me, but they did. It was just soooooo slow.
  • -4 Hide
    ethaniel , December 30, 2009 6:03 AM
    That thing's not even backwards-compatible with actual motherboards. The only reason that could make me adopt UEFI is to "flash it" somehow in my current motherboard. And if you can't boot over 2 TB, bring the old DDO's back! Let the hard drive makers to provide a solution. I know current BIOSes are overpatched and overextended, but you can't just shoot in the head a technology used for 25 years. It's like "let's remove the driving wheel of all cars, tomorrow". "Transition" is the word. UEFI is not ready yet. Period.
  • 5 Hide
    Anonymous , December 30, 2009 6:31 AM
    Motherboard manufacturers(people who know lots about these things) arent going to it.
    Consumers arent going to it.

    2 people at toms hardware really arent going to change anyone's mind.

    Yes bios is aging and old. The reality though... unless uefi was bringing something to the table like openstandards and thusly open source firmware for all motherboards... at least something if not that. Hell it's kind of the complete opposite isnt it? They are pretty much moving toward open source bios isnt tagging along. That's a pretty good chunk of people who have a clue about the tech; who are going to look at this with contempt. The on your fence people looking for reviews who find both sides and pretty much everyone who is educated on this subject is more or less uninterested in it; if not hate it.

    As someone who isnt in the educated group. All I see is no value in touching this. Infact it almost certainly is a bad idea to get into it. RDRam anyone?
  • 14 Hide
    Anonymous , December 30, 2009 6:37 AM
    Excellent article, I've been musing about this myself but never got around to reading up on it. Shame to get official confirmation that motherboard makers are so far behind though.

    The current BIOS really needs to be done away with.

    Much like PATA, Serial and Parallel ports, PCI slots, Floppy connectors, PS/2 connectors, FireWire or the other odds and ends of legacy hardware interfaces that we still pay to have added into modern systems.
  • -2 Hide
    Anonymous , December 30, 2009 7:13 AM
    Macs been using efi for a while now!
  • 2 Hide
    Jaspel , December 30, 2009 7:29 AM
    haplo602have been using EFI on various HP model itanium servers. it is quite nice what it can do. however it needs major modifications for desktop use (a friendly GUI for a start).

    not to mention ia64 bootable utilities.
  • 1 Hide
    pkellmey , December 30, 2009 10:25 AM
    There is little market need right now; there is little that the end user immediately sees as "must haves" in its current state. No market equals no manufacturer willing to stick its rep on it in any real way. Dead on arrival.
  • 0 Hide
    cappster , December 30, 2009 10:58 AM
    Great Article Patrick and Achim! I was unfamiliar with this new boot process, but it sounds very intriguing. I believe with the new higher capacity drives that are coming to the market, it won't be long before the community will start really driving the MB manufacturers to step up to the plate. Lets face it, as computers continue to evolve, the average joe is starting to make use of higher storage capacities and faster read/write capabilities. Everything is moving to HD and which equates for better storage solutions. As far as overclocking goes, I can see the UEFI allowing for greater overclocking flexibilities and possibly more stability across different OS's that us, the enthusiasts, have stored on our computers.
  • 0 Hide
    liquidsnake718 , December 30, 2009 11:18 AM
    Wow another paradigm shift in the way we will work with our motherboards. I guess the days of the X58, and P55 are numbered and newer ones will steadily replace them! I hope we can actually "download: these bio's ainstead on our "older" boards....
  • 3 Hide
    mcshasta , December 30, 2009 11:41 AM
    mongo67Macs been using efi for a while now!


    Too bad a 2TB+ hard drive placed in a mac costs an additional $250+ for no reason at all.

    Good luck placing it in there yourself without voiding their warranty.
  • -6 Hide
    lradunovic77 , December 30, 2009 11:57 AM
    I read this article and i still don't see any benefits of UEFI. I don't think we need it, BIOS we have now is good enough and i think Industry don't see any benefits of UEFI. Having said that, move on.
  • -5 Hide
    deanjo , December 30, 2009 11:58 AM
    McShasta
  • 0 Hide
    deanjo , December 30, 2009 11:59 AM
    mcshastaToo bad a 2TB+ hard drive placed in a mac costs an additional $250+ for no reason at all. Good luck placing it in there yourself without voiding their warranty.


    Every Mac that has a replacible or additional harddrive bays allow the use of standard harddrives. Same price as PC's.
  • 3 Hide
    iwod , December 30, 2009 12:11 PM
    I hope toms hardware will digg deeper. Since no one article on the net has covered enough details. Why is BIOS bad? What will UEFI brings that i can not do today.
    It points out that UEFI in itself is like an OS. Which is true, as Linus has put it, UEFI is adding another complex layer. BIOS is good because it is Simple.
    With tweaked SSD and systems. Intel has proved that an Linux system can be booted in less then 4 seconds. I dont know how many seconds BIOS contributed to this time, but my guess is UEFI wont make it that much faster.
    So, what is the point of UEFI, can we just cleaned up BIOS instead?

    Would love someone to tells us the details.
  • 0 Hide
    tester24 , December 30, 2009 12:14 PM
    I have to say that I was waiting for the change. Just bought the DP55KG and didn't even know I could impliment UEFI. Can't wait until it becomes the norm. Been using it on the Itanium machines we have at work and I like it especially in multiboot scenarios.
  • 0 Hide
    lradunovic77 , December 30, 2009 12:18 PM
    Macs are nothing but PC (with joke components in it).
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