The factors that influenced PATA desktop hard drive performance could be counted on a few fingers. Rotational speed and data cache were the two main factors, but the advent of Serial ATA has really opened up the door. Now, technologies like NCQ have transformed the way data is transferred to and from the disk, and the latest SATA 3.0 Gb/s has brought burst mode performance to new heights. When you factor in the larger data caches, this adds a whole lot to the performance bottom line. The two drives we're looking at today epitomize this progression, and both the Seagate Barracuda 7200.9 300GB and 500GB drives offer not only SATA 3.0 Gb/s and NCQ support, but include a full 16MB of on board cache.
The Seagate Barracuda 7200.9 300GB and 500GB drives may offer different capacities, but these are equivalent in terms of features. Both drives offer a 7200-RPM spindle speed, an average seek time of 8.5 ms, an average latency of 4.16 ms, and 16MB of segmented data cache. Most of these specs are consistent through the line, but only the 7200.9 drives with capacities of 300GB or higher have the full 16MB of cache, while the 250GB and lower models sport only 8MB. The Barracuda 7200.9 300GB and 500GB hard drives also feature the latest SATA 3.0 Gb/s interface and have support for NCQ (Native Command Queuing).
The Seagate Barracuda 7200.9 design is very standard, and offers the same basic features as many other SATA models. The drive back plate includes Serial ATA power and data connectors, and as this is a relatively new drive, there are no Molex connectors or any other legacy ports available. The top of the drive housing is silver with the Seagate model number and specs, along with a diagram of the SATA power and data connectors. As SATA is serial technology, there is no need for jumpers for Master or Slave drive configuration.
SATA 3.0 Gb/s is intended to be backward compatible with the original SATA 1.5 Gb/s standard, but as with most things in life, this is not written in stone. We had no problems on our legacy SATA platforms, but there is no possible way of testing every single permutation. To help alleviate any potential issues, Seagate has included a special jumper, which if enabled, limits the drive to SATA 1.5 Gb/s transfer rates.
The actual internal architecture of these Seagate Barracuda 7200.9 hard drives has been the subject of much debate, especially as the conventional "model number" format does not seem to work. We went straight to Seagate for the answers, and found that the Seagate Barracuda 7200.9 300GB drive features 3x100GB platters, while the 500GB model utilizes a 4x125GB format. We've also included a chart below outlining the platter size and number for the various Seagate Barracuda 7200.9 models, which might bring up as many questions as it answers.:
* Note that the Seagate Barracuda 80GB model (1x160GB) is not a misprint, and due to its architecture (160GB platter + 1 head) is prized by some enthusiasts for its high-performance, yet silent, operation
Since we are using an NVIDIA nForce4 Ultra motherboard board for our testing, here are a few screenshots (click for larger view) showing the two Seagate Barracuda 7200.9 drives and their associated features. Note that both are properly identified as second-generation Serial ATA 3.0 Gb/s drives, and have NCQ enabled by default.
The Seagate Barracuda 7200.9 drives support the latest SATA 3.0 Gb/s standard, or what was originally code-named "SATA II". This effectively doubles the potential data throughput, and SATA 3.0 Gb/s translates to an approximate 300 MB/sec. real-world data transfer, compared to 150 GB/sec. for standard SATA. This has caused many vendors to list these drives as SATA 300 and SATA 150, just to simplify things. There were some additional improvements in the specification, such as Native Command Queuing, Staggered Spin-Up, and Hot Plugability, among others. The top feature is obviously the higher interface speed, and while current drive technology holds it back in a single-drive configuration, drive arrays can yield better results due to a larger data pipe for inter-disk transfers.
While current hard drive technology does not push the sustained data transfers of the latest SATA 3.0 Gb/s standard, there are other benefits. One of these is noticeably higher burst mode speeds, where the onboard drive cache sends data straight from memory in a high-speed burst operation. This does allow for higher performance in some circumstances, but true to its name, burst mode transfers cannot be sustained and only allow for temporary performance spikes. The data source also impacts overall burst mode performance, as small and/or sequential data works best, and allows both read and write operations to transferred to the host at a blazing 300 MB/sec. rate. Other external factors enter in, such as the size and speed of the data cache, which is one reason many of the higher-end SATA 3.0 Gb/s drives feature 16MB of onboard cache.
NCQ, or Native Command Queuing, is a feature that lives up to its name, and allows multiple commands to be queued simultaneously, all within the same physical drive. These commands can then be dynamically rescheduled to provide the best overall performance. That means if a command comes in for data that exists in close physical proximity to data just retrieved or written, then NCQ would put that command at the top of the list and increase overall disk performance. The benefits of NCQ are clear, as it provides a low-cost, high-performance hard drive, all without the potential heat and noise issues that come with increasing rotational speeds. SATA 3.0 Gb/s is also backward compatible with SATA 1.5 GB/s, and the interface speed will be dependant on the both drive and controller Serial ATA support.
Native Command Queuing is an interesting feature, as it is both optional to the SATA spec and available in both SATA 3.0 and 1.5 Gb/s implementations. This is the case with the Seagate Barracuda 7200.9 (SATA 3.0 Gb/s) and 7200.8 (SATA 1.5 Gb/s), which each offer NCQ support.