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

  • Pastuch - Tuesday, August 24, 2010 - link

    I am very confused on why the 3tb drives were not released as OEM. People looking for this kind of space are not looking to put the OS on that drive.

    Why not release the 3tb drives now, let us create GPT partitions in Windows and use the storage space. I need 12 terabytes ASAP! I would rather 4 drives instead of 6. Hopefully WD catches up soon.
  • Bytales - Wednesday, August 25, 2010 - link

    I didn't knew long heat means performance degradation in such a way that it reaches the jaw-dropping 1mb/s.
    In these cases, flash ssd seem to have the advantage. However, we still have to wait until ssd become more capacitous than hdd, to the point that creating a hdd is no longer worth it.
  • loekf - Sunday, August 29, 2010 - link

    Get a Western Digital MyBook 3.0, they only come in 1 TB and 2 TB flavours, but these keep itself cool. After copying 700 GB of data, temperate was steady at 43 celsius. Reply
  • mewgirl - Monday, January 31, 2011 - link

    Except, don't, because they require a separate plug, are absolutely humangous (literally, about 3" in DEPTH!), and will last about 2 weeks. Reply
  • dragunover - Saturday, August 28, 2010 - link

    Seagate is terrible. In my own experience, it's been the only hard-drive out of many to fail. By far, I've had at least 4 Hitachi, 4 WD's, and a Samsung and none of them have failed. Then again, there's also the user-reported failure rates which report Seagate among the top...
  • MrSpadge - Saturday, September 4, 2010 - link

    Hey Anand,

    you're doing a really great job on SSDs, but heres one paragraph I really disagree with:

    "... and sequential performance is actually down from the 2TB drive due in part to the fact that we've got a smaller cache and generally less performance optimized drive with this external 3TB unit compared to the 2TB internal drive. Over USB 3.0 we actually get much better sequential performance apparently due to some additional buffering done by the USB 3 controller."

    You're running into some bottleneck here using the internal SATA for the 3 TB drive. Was it in IDE mode? Or maybe just SATA1? If you take a look at the performance over capacity using this SATA port I bet you'll see a straight line at ~120 MB/s until about 1.5 TB and then a drop similar to what you're showing on the page "Performance vs. Capacity".

    The reason is simple: on that page you're showing the drive hitting performance >120 MB/s over the entire first 1.5 TB using the USB 3 connection. This test is a sequential test over the entire drive, so ne pauses in between. Were this speed due to a buffer it had to be at least 1.5 TB big. Otherwise what you're seeing here is the real sequential performance of the drive.

    And HDD caches influence real world benchmarks, but do not influence such sequential tests (think of it: even 64 MB are filled in just 0.5 s for such a drive, afterwards it's just plain "write them as fast as you can").

    Best regards,
  • Rloew - Friday, October 1, 2010 - link

    With some minor modifications to the MBR and FIlesystem code, the bare Hard Drive can be booted from without EFI and used in DOS and Windows 98SE. The USB 2.0 Interface can be used in Windows 98SE with a couple of Patches. Reply
  • Agent24 - Monday, October 18, 2010 - link

    It makes no sense, unless they just didn't think to test what might happen to the drive temperature when stuck inside that little box and made to write data (who does that?)

    If it was cost, then that's stupid.

    I expect these are quite expensive already, being new and 3TB. What's an extra $50 or whatever to get a decent case with some proper cooling vents or even a fan?

    I definitely wouldn't buy one of these, not until they made a better case, and even then, I want to see the reliability of the drive itself.
  • The Sorcerer - Saturday, December 25, 2010 - link

    On the 2 paragraph, 4th page you said:
    "While you can plug a SATA power cable directly into the drive, the enclosure prevents you from sticking a SATA data cable in there - not without trimming away part of the plastic surrounding the cable’s SATA connector at least."

    You don't need to trim it. The SATA cable from the Asus boards are slightly thinner connectors. You should be able to do it. I've done it on the Seagate GoFlex 500GB PRO review:

    Infact, when you run Crystal DIsk Information even when the drive is connected via USB mode, it detects the model but it will show that its scaled down to SATA 150 (I got a USB 2.0 as a sample).

    Just my 2 cents :).
  • infoage2000 - Monday, July 21, 2014 - link

    I have (or had) this 3 TB drive, and three months later it has died. The error; drive needs formatting. So in hopes it was the enclosure I bought a USB to SATA tester and have confirmed it is the drive. I knew better not to stray from the 1 and 1.5 TB drives which have always been reliable. The one lousy time I don't have backups for two directories I copied over....shaking my head in disgust. Reply

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