Western Digital WD740ADFD: Bottled Lightning

The original Western Digital Raptor was launched as the WD360GD in March of 2003 with an enterprise level 10,000 RPM spindle speed, SATA interface, 8MB buffer, 5.2 millisecond read seek time, and a single-platter design featuring 36GB of storage. While it shined in single-user performance, the drive did not fare well against its SCSI-based competitors in the enterprise server market for which it was designed. Its already small size and complete lack of command queuing abilities delivered performance that was not on par with the SCSI drives in the critical multi-user applications. However, due to the lack of entry level SCSI drives, a growing interest in SATA components, and a very avid computer enthusiast market, the drive was able to succeed until its replacement arrived.

The next version of the Raptor was launched as the WD740GD in December of 2003 and boasted several needed enhancements. These enhancements included the addition of another platter that increased the capacity to 74GB, 4.6 millisecond read seek time, a FDB based motor to address noise concerns, and ATA-4 tagged command queuing. While TCQ was a welcome addition and certainly improved the drive's I/O operations, it still was not a match for most SCSI drives in the enterprise market. This was primarily due to a lack of SATA controllers that fully supported TCQ and firmware that was not as mature as the SCSI competition.

However, this drive was - and in certain cases continues to be - consistently one of the faster single-user performance drives available. The computer enthusiasts flocked to the drive due to its performance advantages, but the drive continued to have limited success in the enterprise server market. In a nod to the success of the drive in the computer enthusiast market and acceptance of its importance, Western Digital offered the drive in retail stores for a short time. Over the course of the last couple of years, the 8MB cache drive has been enhanced with minor revisions with one of the latest versions, WD740GD-00FLC0, receiving tweaks that significantly improved its performance in single-user applications.


The last major update to the Raptor family occurred in January of 2006 when the WD1500ADFD was launched with a significant list of improvements. The drives still sported the familiar 10,000 RPM spindle speed, 4.6ms read seek time, and a two-platter design now at 150GB capacity. The platter's density was increased to 75GB+ and equals those of several 10,000 RPM SCSI competitors. The buffer size was doubled to 16MB, matching the latest offerings from other drive manufacturers. An OEM version of this drive was made available by Dell that sported a 160GB capacity. WD also introduced a limited edition Raptor-X that featured the 150GB version with a crystalline polycarbonate based transparent cover over the spindle and platter section of the drive.

The Marvell 88i8030 PATA to SATA bridge chip that was used on the previous Raptors was finally dropped in favor of a native SATA implementation. This native SATA implementation brings with it Native Command Queuing instead of the legacy firmware-level Tagged Command Queuing. While NCQ can have a favorable impact in multi-user applications, it can create a performance penalty in certain single-user applications. Since the drive is still targeted towards the server market, it retains the first generation 150MB/sec SATA interface instead of the 300MB/sec SATA interface found in most of the current consumer level drives.

The WD1500ADFD also introduced Time Limited Error Recovery (TLER) and Rotary Acceleration Forward Feed (RAFF) operations to the Raptor product family. TLER allows the drive to signal the RAID host adapter in the event an error recovery process has exceeded timeout parameters. This prevents false drive dropouts on the host adapter when utilizing RAID level 1 or above configurations. Although TLER is disabled by default, a utility is available from Western Digital to enable TLER. RAFF is an electronics feature that senses rotational vibration in a multi-drive setup and then compensates for it by controlling the drive head location. This feature is designed to keep read and write operations consistent, thus avoiding time consuming retries by the drive that could impact performance.

The latest updates to the Raptor family occurred last fall when Western Digital offered the same features introduced on the WD1500ADFD on its 74GB and 36GB drives. The current WD740ADFD also sports a single platter design now instead of the previous two platter design in the older series. We will be taking an abbreviated look at the WD740ADFD today as we received numerous comments and emails inquiring about the performance of this drive. Our next storage review featuring several of the latest 500GB drives will include full performance results of this drive and its smaller sibling, the 36GB Raptor WD360ADFD. For now, we think the performance results we will present today should give a clear indication of the drive's performance.