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  1. #1
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    Up against the 2TB drive-size ceiling




    LANGALIST PLUS

    Up against the 2TB drive-size ceiling


    By Fred Langa

    The classic Master Boot Record (MBR) format maxes out at 2.2TB; you can't use MBR formatting on partitions larger than that. But a relatively new formatting standard GPT can handle drives of any size you'll likely encounter in the foreseeable future.


    The full text of this column is posted at windowssecrets.com/langalist-plus/up-against-the-2tb-drive-size-ceiling/ (paid content, opens in a new window/tab).

    Columnists typically cannot reply to comments here, but do incorporate the best tips into future columns.

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    "...10 zettabytes (ZB). (Zetta- indicates a one followed by 21 zeros! ....It'll be a long, long time before we outgrow GPT."
    Made me smile. You are probably right, but it made me think way back when a colleague and I bought a hardware controller with a big DEC mini-computer to run it. It came with a choice of 5 or 10 MB hard drive. We looked at each other and said wow!, 10 MB let's go for it, we'll never need that much space in our lifetime! Never say never...
    Rich W.

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    If you want to format your 4TB drive using MBR, you need to split it into two 2TB partitions.
    From the article. I don't think that's true is it? I thought the MBR can only address 2.2 TB of a drive, period, and that it cannot address two separate partitions of less than 2.2 TB but far more than 2.2 TB in aggregate. Without the proper Disc Wizard from Seagate anything above 2.2 will not be visible just as XP pre SP2 was limited to only seeing 137 GB or less of a drive's capacity.
    Last edited by F.U.N. downtown; 2013-03-21 at 17:04.

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    In Fred's article a contributor mentioned Ad-Aware and its hijacking of the search engine - my update did the same, but mine is the 'Pro' paid version. I had to reset my home-page twice before the system got the message!

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    Hi Fred, I was surprised and a bit confused about your statement that MBR can only support 2.2TB partitions. I recently bought a new 3TB Seagate drive and, not knowing any better, formatted it with a single NTFS partition. It's not my boot drive; it's an eSATA connected drive that I use for backups. My windows Disk Management utility is claiming that it's a 2794.30 GB NTFS Primary Partition. Did I unknowingly work some magic to get it to see the full 3TB or did I misunderstand your article?

    3TBdrive.jpg

    -Ken

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    Quote Originally Posted by vorlonken View Post
    Hi Fred, I was surprised and a bit confused about your statement that MBR can only support 2.2TB partitions. I recently bought a new 3TB Seagate drive and, not knowing any better, formatted it with a single NTFS partition. It's not my boot drive; it's an eSATA connected drive that I use for backups. My windows Disk Management utility is claiming that it's a 2794.30 GB NTFS Primary Partition. Did I unknowingly work some magic to get it to see the full 3TB or did I misunderstand your article?

    3TBdrive.jpg

    -Ken
    Go back and right click on the area where it says Disk 1 and choose properties and under the Volume tab look at what the partition type is. If it says GPT you solved the puzzle, if it says MBR then its a mystery to me as well.

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    You're right, it is a GPT partition. The reason I assumed that it wasn't is becuase of your statement below:

    On PCs, full GPT support requires 64-bit Windows (Vista or later) and a UEFI (Universal Extensible Firmware Interface) BIOS.
    I have a plain old BIOS as far as I know. My motherboard is an ASUS m3a32-mvp deluxe (AMD Phenom compatible) and the box isn't bragging about UEFI, that would have been a very new feature when I bought it. I am running win7 ultimate 64-bit.
    Last edited by vorlonken; 2013-03-22 at 18:14. Reason: typo

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    Quote Originally Posted by F.U.N. downtown View Post
    From the article. I don't think that's true is it? I thought the MBR can only address 2.2 TB of a drive, period, and that it cannot address two separate partitions of less than 2.2 TB but far more than 2.2 TB in aggregate.
    Yes, another blunder from Fred. I'm getting worried about some of the things he write that is just plain rubbish.

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    Quote Originally Posted by F.U.N. downtown View Post
    From the article. I don't think that's true is it?
    It sort of is, but I don't think Fred understands why (he's kind of loose in differentiating between partitions and disks, for that matter).

    Leaving aside the legacy cylinder/track/sector addresses (which are now pretty much ignored in 'LBA-style' MBRs), each of the 4 partition entries in the MBR contains a 4-byte start sector address and a 4-byte partition size field, each of which can be a number from 0 (indicating no partition present in that entry) to 2**32 - 1. So you could have a partition just under 2 TiB in size (2**32 - 64 512-byte sectors) followed by another partition the same size occupying your 4 TiB disk and still represent them using MBR-style format, because the MBR doesn't need to represent anything but the FIRST sector of the second partition in a 32-bit number. (Your 137 GB analogy was close but not quite on target, since that limit applied to ANY access beyond that range: this may be more like an older 8ish GB limit associated with early Win9x systems, IIRC involving a 1024 cylinder addressing limit, where the boot sector of a partition had to reside below this address for the partition to be bootable but the REST of the partition could extend beyond it).

    Now, any operating system that internally used 32-bit numbers for absolute disk sector addresses would most certainly barf and/or cause serious corruption if it tried to address data in the second partition, but that's an OS limitation, not an MBR limitation (and recent Windows and Linux systems do, in fact, use larger internal fields to handle absolute disk sector addresses, hence should work OK for this). Whether various disk-management applications would get confused is anyone's guess, though, so I'd be pretty leery of putting this to the test (and I don't think it's what Fred was talking about anyway: I suspect he was confused about what Seagate's driver appears to be doing, which is breaking the 4 TiB disk up into 2 2TiB virtual DISKS, each of which has its own MBR to control partitioning within it).

    I thought the MBR can only address 2.2 TB of a drive, period
    Not quite. There's another way for MBR-style partitioning to address more than 2 TiB on a disk (and also to support individual partitions larger than 2 TiB): using larger disk sectors (e.g., the 4 KB sector size used on 'Advanced Format' disks). Windows has supported sector sizes other than 512 bytes (and up to 4 KB) at least since later releases of NT, at least for data disks (whether BIOSes would let you BOOT from such a disk is another question, though, even if Windows would), and thus you could use an Advanced Format disk that actually reported its sector size as 4 KB (rather than pretended it was still 512 bytes to provide transparent legacy support) with MBR-style partitioning to address up to a 16 TiB disk with up to 16 TiB partitions on it (2**32 - 1 4KB sectors).

    Quote Originally Posted by vorlonken View Post
    I have a plain old BIOS as far as I know.
    I don't know where your quote preceding this came from (edit: now I see that it was from Fred, but you seemed to be addressing FUN) but its use of the phrase 'full support' includes boot support, which you are not using. Data (but not bootable) GPT disks on Vista and later Windows systems require neither 64-bit nor UEFI support.
    Last edited by - bill; 2013-03-24 at 00:18.

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    Hi Fred and/or anyone that can help,

    This is a follow up question to Jeff Jones question, that you ansewerd in Issue 378 2013-03-21 .

    I also have a Seagate 4TB external drive and cannot make an image of drive C. I am using Windows 8, and have tried making a image with Windows 8 backup software, EaseUs ToDo, and DiskWizard. Prior to using DiskWizard, when the drive had the Advance Format 4K, I could back up data with both Windows 8 and EaseUs, but when it came making an image I would get reports that there was not enough space, or sectors didn't match. After using DiskWizard to make two partitions, I first attempted the MBR format and made both partitions logical drives. After formatting the Seagate drive; Windows 8 could not find either partition, or sometimes it would find the second partition, but not the first partition on the drive.

    So I had to switch to GPT format, I first made one partition, then I made two partitions, and the outcome for either format was the same. I could backup data using all three softwares, but could not make an image file.

    DiskWizard; using the" clone" feature treated the 4TB drive as one partition; whether it was partitioned or not. It would list the Seagate drive with 3.69TB, but not let me select the it as the Target.

    Windows 8, using "Create a system image", the program would take me through all the steps. It recognized both partitions and reported the correct size of each partition. I needed 322GB to make an image of drive C, and Windows showed I had 169TB available in the partition I selected as the Target. After hitting the Start backup button, it proceeds to create a backup, but then I get a message stating backup failed due to not enough disk space.

    EaseUs; using "Disk Clone", the program sees both partitions, and the correct size. It also shows that drive C and the Seagate drives have the same GPT (NFTS) format. The program allows me to select the drive but not an individual partition. When I click "next" to make the clone I get a message "Sector Size of destination disk and source disk is inconsistent".

    I really feel uncomfortable not being able to make regular images of drive C. That drive is a 2TB drive, so I will need a large drive for my images and backups. If I can't get my 4TB drive to store images, should I just go ahead and purchase a SATA drive and SATA drive enclosure for my data and image backups. Or will I come across the same problems that I am having with my Seagate 4TB external drive. I already experience problems trying to make an image with the 4K format that my Seagate 4TB originally came with.

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    Data (but not bootable) GPT disks on Vista and later Windows systems require neither 64-bit nor UEFI support.
    Is that true for 3 and 4 terabyte drives? If not, it might be important to add that conditional.

    For formatted, you aptly demonstrate the problems there can be with large drives. It's an "all your ducks in a row" operation and you seem to be missing one duck. What EaseUS program are you using exactly? I don't think Disk Copy will work since it is a sector by sector program and needs to wipe out the destination disk formatting. If you are trying the latest ToDo free version 5.6, don't clone the disk or a partition with that either, rather just try the backup partition/disk image portion and see if you have better luck.

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    Quote Originally Posted by F.U.N. downtown View Post
    Is that true for 3 and 4 terabyte drives?
    Good question - I had to look up the answer. Apparently Microsoft re-wrote only a portion of the 64-bit XP driver stack to support GPT without re-writing the portion that used 32-bit fields to address raw sectors on the disk, but for Vista it did the latter as well (though NTFS still limited the maximum file system size to 256 TiB, which won't suffice all that much longer, especially considering that some RAID or RAID-like facilities could already present a 'disk' larger than that).

    Edit: I'm sure you understood this, but for the possible benefit of others I should have included the statement that the simple answer is 'yes'.

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