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


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  • mxnerd - Monday, August 23, 2010 - link

    10 years ago Seagate is all about quality. Not any more. Every retail drives ( more than 5) I bought from Seagate in the past five years gone bad before the 5-year warranty.

    The problem with Seagate drives? They are too hot.

    WD only gives you 3-year warranty for their drives, but I'm buying them exclusively now.
  • mewgirl - Monday, January 31, 2011 - link

  • Sottilde - Monday, August 23, 2010 - link

    Hard to believe the engineers could be thick enough to put a mesh grille on the side for looks only, without providing any actual ventilation. A major oversight IMO, especially if you tend to pound on your hardware. Reply
  • Indigo64 - Monday, August 23, 2010 - link

    I realize this site and its standing on the web, but Google's test results show that hard drive temp isn't a factor for failure rates - at least not in the same manner in which people get all uptight about it.

    I have a laptop at home where the hard drive runs constantly around 50*C and it hasn't ever failed on me. I have a desktop system that has drives that run below 40*C and it's gone through three already.

    "One of our key findings has been the lack of a consistent
    pattern of higher failure rates for higher temperature
    drives or for those drives at higher utilization levels.
    Such correlations have been repeatedly highlighted
    by previous studies, but we are unable to confirm them
    by observing our population. Although our data do not
    allow us to conclude that there is no such correlation,
    it provides strong evidence to suggest that other effects
    may be more prominent in affecting disk drive reliability
    in the context of a professionally managed data center

    Interpret how you will, but if Seagate says this drive is fine without any active cooling, then why do people need to ding the drive for this "oversight"? It's all perceived performance stats in the PC realm - if it's hot, cool it down. If it's cool, don't bother it.
  • GeorgeH - Monday, August 23, 2010 - link

    I don't have it in front of me, but IIRC the temperature range of that Google study was something like 10-50C, and they found that the sweet spot was 30-40C. 60C+ (as in this Seagate drive) isn't a "perceived" problem, it's a measurable one; re-read the paragraph where Anand found transfer rates dropping by 60%+ as the drive went into that range. Reply
  • wiak - Monday, August 23, 2010 - link

    ooh the irony ;) Reply
  • conwayboys - Monday, August 23, 2010 - link

    Never ceases to amaze me why computer and drive manufacturers do not design cases with natural convection, struck me the other day at work when the IT boffins had a major crash due to a faulty fan in the server room. WTF there were three of them standing around designing a new air conditioning system for the server room. I got the step ladder and removed 4 panels from the false ceiling to allow the heat to escape into the roofspace, instant temperature drop, so why cant we employ the same thinking to computer cases and drive cases vent the top and the bottom ensuring hot air rising will pull cold air in from the bottom, obviously spillage issues with moisture getting in the vents, so the vents can be on the sides near the top with the fins slanted downwards still allowing hot air to escape. Reply
  • compuser2010 - Monday, August 23, 2010 - link

    32-bit Windows 7 also supports GPT. However, only for *data* disks/arrays; even if the capacity is less than 2 TB. Formatting using GPT can be done in "Computer Management."

    2 TB may seem like a huge amount of memory to some. But it is an increasingly paltry amount of memory for those who edit video (especially uncompressed) and who work with Blu-ray Discs (copying a disc to another disc, copying discs to a computer, authoring discs, leaving those disc projects on the computer for a while, etc.).
  • Randomblame - Monday, August 23, 2010 - link

    oh wait that was ram... still. I could use 3tb right now but 5 platters - that's too many. I'll be waiting. My current setup is 3 500gb seagate baracuda 7200.12s in raid 0 backed up by a 2tb cuda. That way I've got only 3 platters spinning for low noise, reliability, and high data density. Though this thing uses 600gb platters which is nice I think I'll wait a bit maybe we'll get some higher data density per platter while we're waiting for microsoft and motherboard vendors to get this 2tb cap fixed. Reply
  • futbol4me - Tuesday, August 24, 2010 - link

    anyone know? i have an external 2.5" drive hanging off my apple extreme router that spins 24/7 but was wondering if newer external drives have some power savings features. Reply

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