WD Red Pro Hardware Enhancements

Physically, the WD Red Pro family of hard disk drives is almost identical to the WD Black family of high-performance desktop hard disk drives. Probably the main physical difference would be the inclusion of 3D Active Balance Plus, and hardware vibration compensation technology.

3D Active Balance Plus, which Western Digital touts as an "enhanced dual-plane balance control technology", is also found in the WD Red family of NAS drives. It reduces the amount of vibration produced by the WD Red Pro hard disk drive, which not only improves the reliability of the Red Pro drive itself, but also other drives in the NAS system. It also has the beneficial side effect of making the drive slightly quieter, shaving off a decibel or so.

The hardware vibration compensation technology, however, is exclusive to the Red Pro drives and not available in the WD Red family of drives. Together with the multi-axis shock sensor, the drive is able to detect and compensate for even subtle shocks and vibration, allowing up to 16 Red Pro drives to be used simultaneously in a single NAS unit! In the past, you would have to use the far more expensive Western Digital Se enterprise-class family of drives to populate large NAS systems.

The 4 TB Western Digital Red Pro uses almost twice as much power as the 4 TB Western Digital Red during reads and writes, as well as while it idles, because it spindles at 7200 RPM, instead of just 5400 RPM. However, Western Digital managed to keep the Red Pro's power consumption 10% lower during reads/writes and 20% lower while idling, compared to its desktop equivalent drive - the 4 TB Western Digital Black hard disk drive.

The lower power consumption is important because it means the drive produces less heat. With so many drives stacked together in the enclosure, a lower thermal output would increase the drives' reliability. In the FLIR comparison on the right, they demonstrated how much cooler the WD Red drive is, compared to an unidentified competitor's hard disk drive. However, it is not known if the competing drive is a 5400 RPM or a 7200 RPM hard disk drive.

The lower thermal output also allows the WD Red Pro drive to work in hotter conditions. While the equivalent 4 TB Western Digital Black drive is rated to work at ambient temperatures of up to 55°C, the 4 TB Western Digital Red Pro can work at a higher ambient temperature of up to 60°C.

Finally, WD Red Pro drives undergo more rigorous factory qualification tests, allowing Western Digital to give them a MTBF rating of 1,000,000 hours, which is the same rating for its desktop equivalent. However, in the Red Pro's case, the 1,000,000 hours is the rating when used in the packed confines of an 8-16 bay NAS enclosure!

To give you an idea of what that means, a NAS system with 8 Red Pro drives will likely see a single drive failure after 14.3 years of non-stop operation. In a NAS system with 16 Red Pro drives, that would drop to 7.1 years - still a very good indicator of reliability.

Western Digital NASware 3.0

The WD Red Pro's other advantage lies in its NASware firmware, which Western Digital has upgraded to version 3.0 for the Red Pro family. This is how the new NASware 3.0 firmware helps the WD Red Pro differentiate itself from standard desktop hard disk drives :

• Compatibility - NASware 3.0 has been extensively tested with key small NAS system providers.

• Streaming support - NASware 3.0 provides built-in compatibility with the ATA Streaming Feature Set which is important for AV storage applications such as Windows Media Center

• SMART Command Transport (SCT) support - NASware 3.0 allows monitoring and measuring of drive performance via the SMART command set. SMART can return data like thermal profiles, drive access statistics and more. NASware 3.0 also delivers temperature accuracy within 1°C.

• Power management support - Enables optimized power usage within the NAS system and protects your data in the event of a power loss or disruption.

• Lower power consumption - NASware 3.0 optimizes power use resulting in significant power savings and lower hard drive operating temperatures. This improves the overall reliability and performance of the drive and reduces the NAS cost of ownership.

• BIC Performance - Optimized seek to provide BIC performance while reducing the power and acoustics.

• RAID-specific, time-limited error recovery (TLER) - NASware 3.0 also prevents hard drives from being dropped off the RAID due to extended error recovery. This provides more availability and less down time rebuilding the RAID.

• Command completion - To further improve reliability, NASware 3.0 minimizes the data corruption or loss in the event of an unexpected power loss by completing the command in process before shutting down.

TLER Support

All modern hard disk drives are designed to automatically correct read and write errors and protect against further data corruption by remapping bad sectors with spare sectors. This remapping process can take anywhere from a few seconds to several minutes to accomplish, depending on the number of bad sectors and the drive's workload.

Unfortunately, RAID controllers are designed to drop hard disk drives from a RAID array if they are unresponsive for more than a few seconds. This is done in the assumption that such a drive has either malfunctioned or is no longer reliable. Depending on the type of RAID array, it can cause the array to lose its data redundancy or force a rebuild of the RAID array from parity data.

To prevent this, the Western Digital Red Pro supports TLER, which is short for Time-Limited Error Recovery. It limits the read error recovery process in the Red Pro drive to just 7 seconds, after which the error recovery process is aborted. This prevents the RAID controller from marking the drive as unreliable and dropping it from the RAID array. The RAID controller can also take over whatever error recovery is left to perform.

You can modify thus default setting using the Western Digital Time Limit Error Recovery Utility (WDTLER.EXE). Many RAID controllers have timeout delays that are longer than 7 seconds, and it is recommended that TLER be delayed for as long as possible. As long as TLER is set to timeout at least 1 second before the RAID controller times out, it will prevent the RAID controller from dropping the drive.

TLER has no performance implications when used outside of RAID arrays. However, it prevents the error recovery process from completing and because there is no RAID controller to take over the error recovery process, detected bad sectors may not be replaced in time. Therefore, it is not advisable to use TLER-enabled drives in non-RAID situations. You can, of course, solve the problem by turning off TLER.

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