The 2TB Barrier

Pretty much all HDDs (and SSDs) are addressed using a scheme called Logical Block Addressing (LBA). The method is very, well, logical. Storage is addressed linearly, regardless of how the hardware itself is accessed. You start at LBA 0 and you go all the way up to the last address in your device. The number of LBAs you can address is a function of your hardware and the style of partition you’ve applied to your drive.

Master Boot Record partitioning is by far the most common on PCs today. LBA 0 contains the Master Boot Record (MBR) and your BIOS looks at the contents of LBA 0 to determine how and what to boot.

Now LBAs under MBR partitions are addressed using 32-bit values, the maximum of which is 2^32 or 4294967296. Each LBA on a hard drive corresponds to a 512-byte sector value (even on current 4K advance format drives, they still appear as 512-byte sector drives to the OS), so the largest partition you can have in a MBR partitioned drive is 4294967296 * 512-bytes or 2,199,023,255,552 bytes.

Hard drive manufacturers define 1TB as 1 trillion bytes. If we use that definition then the largest 32-bit MBR partition would be 2.199TB (2,199,023,255,552 bytes / 1,000,000,000,000). If we define 1TB as 1024^4 bytes (TiB) then the largest 32-bit MBR partition would be 2TiB (2,199,023,255,552 bytes / 1,099,511,627,776). Either way, with a 3TB drive there’s no way we’re getting a single 3TB partition using MBR.

In use on all Itanium and Intel based Macs (among other systems) is GPT (GUID Partition Table), and a feature of GPT is 64-bit LBA support.

With 64-bit LBAs the largest 512-byte sector drive we can address is 9.4ZB (Zettabytes - 10^21 or 2^70 bytes depending on if you’re counting in base 10 or 2). That’s an absurd amount of data.

GPT drives are supported as data drives in all x64 versions of Windows as well as Mac OS X and Linux. Below we have some screenshots of creating a GPT drive in Windows and OS X:

GPT Partition in Windows 7

GPT in Mac OS X

You’ll note that I said data and not boot drives. In order to boot to a GPT partition, you need hardware support. I just mentioned that your PC’s BIOS looks at LBA 0 for the MBR. Your BIOS does not support booting to GPT partitioned drives. GPT is however supported by systems that implement a newer BIOS alternative: Intel’s Extensible Firmware Interface (EFI).

Intel based Macs don’t use a BIOS and instead have an EFI which allows them to boot to GPT drives. Most PC motherboards however do not have EFI support, and those that do may have bugs associated with the implementation.

Case in point is Intel’s DX58SO, which just happens to be my default storage testbed. The good news is that Intel has deployed EFI on many of its motherboards. The bad news is the DX58SO (and potentially other models?) has some serious issues when you enable EFI.

The biggest problem I had was USB support dropping out completely when I enabled EFI on the Intel board. This is apparently a known issue and doesn’t affect all USB peripherals, but it prevented my keyboards and mice from working - which also meant that I couldn’t install Windows.

To make matters worse, even with EFI disabled I couldn’t get a 2TB partition created and installed to. The Windows 7 installer would simply complain that it couldn’t be installed to that drive.

There’s an odd bug with the DX58SO that lets you create a single 3TB partition with the SATA controller in Native IDE mode, and with that you can complete a full Windows 7 install. Note that in Native IDE mode you lose performance benefits like NCQ so it’s not ideal, but it’s the only way to get the drive with Windows installed on it.

Intel is aware of the bug and is working on a solution. Apparently the DP55KG board should work perfectly fine but that didn’t help me in this situation. Update: Intel has since sent me a beta BIOS that addresses a number of these issues, I'm playing with it right now but it didn't make the cut for use in this review. Thankfully it looks like Intel is aware of the problem and is actively working on a solution. I've also asked Raja to pay closer attention to EFI support in his motherboard reviews going forward.

My experience with the Intel board and installing Windows with this 3TB Seagate drive pinpoints why we don’t have an internal drive option for the 3TB Barracuda XT: the hardware isn’t ready for it yet. Consumers are used to buying a new hard drive and just sticking it in their system. With the requirements for EFI and GPT, we’re going to need a lot more effort from the motherboard manufacturers and clear messaging from the drive makers to avoid a lot of confusion in the marketplace.

Not Just Another Upgrade 3TB Internal Drive Performance - Nothing to Get Excited About Yet


View All Comments

  • Quilty997 - Monday, August 23, 2010 - link

    I notice some posters have commented on using RAID 5 with very large disc sizes

    If you do the math using the drive specs and published bit error rates you will find that a RAID 5 array using 1Tb+ discs very soon has a probability not possibility of having a disc error when rebuilding the array.

    For this reason I went to RAID6. (using a dedicated controller to handle the parity calculations).

    Please remember that RAID arrays are not a backup device.
  • Michael REMY - Monday, August 23, 2010 - link

    i can't image the day, even not for my ennemy, where it comes a 3TD hard drive will fail...
    What a lost it will be !
  • mindless1 - Monday, August 23, 2010 - link

    Why would you store valuable data on any one drive alone? Backups, backups backups. Reply
  • JonnyDough - Monday, August 23, 2010 - link

    Until Seagate fixes their longevity issues and can offer a five year warranty that has a better failure rate I'll be sticking with other companies like Western Digital and Hitachi. I used to love Seagate. :( Reply
  • loekf - Monday, August 23, 2010 - link

    Anand, did you actually review the power management features of this drive ? I had the 2 TB model.

    I noticed the same temperature issues and slowless at high temperatures. In my case I got 65 celsius as well.

    Bigger issue I found the power management features, or better said lack of or poor implementation of them. This drive is supposed to be left attached to your PC. There's no on/off switch. So it will power-on and off depending on whether you switch your PC on and whether you access the drive.

    Funny thing it will completely behaves by itself, it has its own will.

    It willl automatically power on again after you SHUTDOWN your computer and you leave it plugged into the mains.

    If you enable sleep mode, it will disable itself when it is not accessed for the specified period. But... it won't go into a sleep mode (= shutting down the drive), no it will unplug in Windows, and after a short period automatically re-insert itself. This means you will see popups or hear beeps indicating that device manager is triggered.

    This is just plain stupid and indicating it's a bad product......
  • mewgirl - Monday, January 31, 2011 - link

    I've never seen a drive that has an on/off switch! Except for the kind that you have to plug in separately, and that kinds of ruins the point of an "external drive" in the first place. Some public places don't even have accessible plugs, they literally put a lock on them. In other words no one would ever buy one unless they just don't know drives sometimes have separate plugs and therefore don't exhaustively evaluate the packing to ensure that the one they are getting doesn't. Reply
  • Aikouka - Monday, August 23, 2010 - link

    Anand, I was curious if you were going to talk about the current USB 3.0 implementation and I was quite glad to see that you did make a note of it! :) But I'm curious... do you know of any motherboard manufacturers that have a better USB 3.0 implementation on the P55 chipset? I know the P55 is literally the red-headed stepchild in regard to its PCI-E bus compared to the X58 (uses PCI-E 1.1 compared to actual 2.0 lanes, has far fewer, etc), but as an example, my ASUS P7P55D-E motherboard uses that "combiner thingy-ma-bob" to combine the PCI-E lanes for SATA 6Gbs functionality. Do any boards do that for USB 3.0? Reply
  • loekf - Monday, August 23, 2010 - link

    Not sure what you mean here. I know for a fact that AMD boards with ATI chipsets use a real PCIe 2.0 x1 lane to the NEC USB 3.0 host controller.

    There is no chipset yet with native USB 3.0 support. All motherboards maker use the same NEC USB 3.0 controller. Though, it seems there are controllers from VIA around, but I didn't see them yet.
  • GeorgeH - Monday, August 23, 2010 - link

    They're talking about P55 and LGA-1156. AMD hasn't made an Intel-compatible chipset in a very long time, and even if they had a P55 compatible license and the desire to make one, LGA-1156's PCIe controller isn't on the chipset.

    As a side note, that's also why LGA-1336 is going to be dead soon after LGA-1155 replaces LGA-1156; the Sandy Bridge derived Nehalem/Westmere replacement is going to have the PCIe controller on die.
  • snakeInTheGrass - Monday, August 23, 2010 - link

    I understand saying that Seagate hasn't released this as a stand-alone drive because the PC hardware just isn't ready yet, but I was hoping they'd try it out on a Mac as well since it sounds like it should just work. It's a shame they won't sell it stand-alone and just label it 'For Intel Mac with EFI' (or hell, just sell it online with a note "For EFI machines only" label for PC users that do have working EFI or an extra internal disk) for the time being because I really don't want to buy another external case. Reply

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