Introduction
Contents
Barracuda XT is the first SATA-600 hard disk drive to arrive the market. It is also the first 2 TB from Seagate that spins at 7,200 rpm – the other 2 TB drive from Seagate, Barracuda LP, is a “green” model spinning at 5,900 rpm. Let’s see if the new SATA-600 interface will really make a difference.
SATA-600 is the third generation from the Serial ATA interface and as you can assume, it presents a maximum theoretical transfer rate of 600 MB/s. This interface is also called SATA 6 G, standing for 6 Gbps. Since SATA works transferring data serially, its transfer rate must be announced as bps (bits per second), which is the unit used for measuring serial data transfers. But since the beginning of times transfer rates are announced in parallel format – i.e., B/s, bytes per second – 6 Gbps converts to 600 MB/s (and not 750 MB/s, which would be the correct conversion from 6 Gbps to MB/s) because the same channel is used for transferring both data and control information. When we remove the control information from the stream, we end up with 600 MB/s.
You also need to keep in mind that this new speed is the maximum theoretical transfer rate from the interface and not from the hard disk drive, and only measures the maximum speed between the SATA port on the motherboard and the hard disk drive controller that is on the drive. SATA-600 drives, especially the first models like Barracuda XT, won’t even reach near that, just like it happened when the first SATA-300 drives were released.
The new SATA-600 interface is physically identical to SATA-300 and SATA-150, allowing you to install SATA-600 drives on motherboards without this interface. So far there are only two motherboard manufacturers providing products with SATA-600 ports, ASUS and Gigabyte, and only on high-end socket LGA1156 motherboards based on Intel P55 chipset. High-Point also offers add-on cards called Rocket 600 that provide SATA-600 ports on any computer with one x1 PCI Express slot available.
Figure 1: Seagate Barracuda XT 2 TB.
Figure 2: Seagate Barracuda XT 2 TB.
Here is a summary of the hard drives we are going to compare:
| Manufacturer | Model | Model # | Rotational Speed | Buffer | Interface | Market | Price |
| Seagate | Barracuda LP | ST32000542AS | 5,900 rpm | 32 MB | SATA-300 | Green | USD 179.99 |
| Seagate | Barracuda XT | ST32000641AS | 7,200 rpm | 64 MB | SATA-600 | Desktop | USD 299.99 |
| Western Digital | Caviar Green | WD20EADS | 5,400 rpm | 32 MB | SATA-300 | Green | USD 209.99 |
| Western Digital | Caviar Black | WD2001FASS | 7,200 rpm | 64 MB | SATA-300 | Desktop | USD 299.99 |
| Western Digital | RE4 | WD2003FYYS | 7,200 rpm | 64 MB | SATA-300 | Enterprise | USD 299.99 |
Western Digital does not inform at what speed their Caviar Green drives spin; 5,400 rpm is our educated guess.
Prices were reasearched at Newegg.com on the day we published this review, except for Barracuda XT, where the price is the estimated price.
Hard drives typically consume between 8-10 W; “green” models consume practically half of this. The trade-off is obviously performance: since they rotate at lower speeds “green” drives present lower performance. Drives from this category are mainly targeted to external enclosures that are going to be connected to the computer through a USB or FireWire port. Since this kind of port limits the drive performance, the hard disk drive doesn’t need to be the fastest around and thus you can save money both on the cost of the drive and on your electricity bill.
Drives targeted to the enterprise segment (i.e., servers), on the other hand, have a higher reliability, as required for this market segment, with some manufacturers providing extended warranty contracts with the drive. With some enterprise-class drives, for example, the manufacturer can ship a new drive in case of failure before the client sends the defective drive to them, reducing the down time of a server.
2 TB hard disk drives have a real capacity of 1.82 TB or 1,863 GB (3,907,029,168 sectors). As you may be aware, the capacity advertised by hard disk drive manufacturers isn’t the real drive capacity. Read our Hard Disk Drives Capacity Limits tutorial for further information on this subject.
Now let’s compare the performance from these five 2 TB drives.