We knew it was only a matter of time before somebody conquered the old 2.19TB partition limit that’s hamstrung drive capacity for the past few years. Since it’s difficult to create a bootable Windows partition on a drive larger than 2.19TB, most vendors have been happily sticking to 2TB drives while waiting for the rest of the computer ecosystem to catch up. But that’s all changing; hard drive vendors are now going full steam ahead on 3TB drives. Seagate and Western Digital already have 3TB external drives, but Western Digital’s four-platter 3TB Caviar Green is the first bootable 3TB drive.
For select values of "bootable."
The 3TB Caviar Green squeezes 750GB onto each platter and boasts 64MB of cache. Its controller is 3Gb/s SATA, not 6Gb/s, but “green” drives aren’t exactly bumping up against the limits of the last-gen SATA spec. But can you use it as a boot drive? And why shouldn’t you be able to, anyway?
Hard drives, historically, have been divided into 512-byte sectors. The Master Boot Record, which tells your computer the location of each sector, is 32-bit, so it can only address a number of sectors equal to 2^32, or 4,294,967,296. Multiply the number of sectors by 512 bytes per sector, and you get 2.19TB. If your partition is any larger, your MBR can’t keep track of all its sectors, and you can’t boot from it. To overcome this obstacle, your PC needs to meet a laundry list of requirements: it needs a 64-bit OS, a motherboard that supports UEFI (the successor to the BIOS) and support for GPT partitions rather than MBR.
If your PC meets those requirements (and its drivers are up to snuff), you should be able to create a bootable 3TB partition on WD’s new 3TB Caviar Green. Just to make sure, Western Digital included an off-the-shelf HBA (Host Bus Adapter) with a carefully-vetted chipset/driver combo—HighPoint’s RocketRaid 62x. Since it has two 6Gb/s SATA ports, the RocketRaid HBA could make this bundle a good value for those needing an extra 6Gb/s SATA port (albeit at the expense of a PCI-e 2.0 slot).
When we finally dug up a board in the Lab that supports UEFI, we were able to install Windows 7 to a 3TB partition on the Caviar Green, but it wasn’t entirely hiccup-free (see Gordon’s how-to, also published today). If you’re not in the tiny percentage of PC owners with a UEFI-compatible motherboard, though, is the 3TB Caviar Green worth getting?
Yes, with some reservations. We tested the 3TB Caviar Green as a secondary drive on our standard motherboard test bed and pitted it against the 2TB Caviar Green (May 2009) and Seagate’s similarly specced 2TB Barracuda LP (October 2009). We tested all 3 drives on the RocketRaid HBA with GPT partitions, to level the playing field. Thanks to the four 750GB platters—the 3TB Caviar Green was the fastest in average sequential reads and write speeds, topping 92MB/s in both.
In our experience, most motherboard southbridge drivers aren’t quite ready for 3TB drives. When we tried formatting ours from the Intel ICH10R on our test bed, it showed up as an 800GB drive—which makes the HBA that WD includes with the drive especially valuable, as it offers a stable driver set for the drive. It’s totally mystifying, then, that WD includes only a half-sized PCI expansion slot with the HBA—the kind you would use for an HTPC, maybe, but not something that works with the vast majority of ATX chassis on the market. To use it in our test beds, we had to remove the PCI cover and leave the HBA dangling from a PCI-e slot. Whether this is a packaging oversight or a bizarre strategic move on WD’s part was not certain at press time, though WD did say that the half-sized card would be in the retail packaging. Until we know more, we won’t be giving the Caviar Green a review score.
The 3TB Caviar Green is fast (inasmuch as a low-power drive can be said to be fast), enormous, and—given that it ships with a useful 2-port 6Gb/s SATA HBA—a good deal at $240. But the percentage of users with the UEFI-compatible hardware necessary to create a 3TB boot partition is still tiny, motherboard SATA drivers are still extremely flaky when it comes to partitions greater than 2.19TB, and the HBA that ensures compatibility only ships with a half-sized PCI expansion slot cover. The drive is fast, but the ecosystem isn’t quite ready for most users.
WD Caviar Green 3TB
WD Caviar Green 2TB
Seagate Barracuda LP 2TB
Avg Read (MB/s)
Random-Access Read (ms)
Burst Read (MB/s)
Avg Write (MB/s)
Random-Access Write (ms)
Burst Write (MB/s)
Best scores are bolded. All drives tested on our hard drive test bench: a stock-clocked Intel i7-930 CPU on an Asus P6X58D Premium motherboard with 6GB DDR3, running Windows 7 Professional 64-bit. All tests performed using HighPoint RocketRaid 62x HBA.