Those features include IntelliSeek – what’s that you say? Well, in older hard drives, the drive head would move rapidly to the point on the drive where the next data is due to be read or written and then have to wait for the disk platter to spin around to the correct sector. Once the data was read or written, off goes the actuator to the next point and again it would sit and wait for the disk to spin to the correct location. That repeated process would lead to additional disk vibration and power consumption. Intelliseek solves that problem by more accurate timing of the actuator movement, so it reaches the right point on the disk just as the platter is rotated to the correct position. Better orchestration of movement equates to less vibration and lower power consumption. So that delivers some of the WD Green drive’s low power credentials.
Another feature you’ll hear mentioned regularly on modern hard drives is “Advanced Format” or “Advanced 4K Format“. This refers to the size of the disk sector, which historically was 512 bytes, but in modern “advanced format” drives produced after 2010 is 4096 bytes. This standard is now adopted across the industry and is supported by all modern devices and operating systems – however, wind the clock back a couple of years, and there were compatibility headaches. Why should you care about Advanced Format? Well, you probably shouldn’t as it’s no longer big news, but it’s an important technology progression that improved storage efficiency greatly – allowing manufacturers to cram more storage space on to those platters.
WD Green drives also benefit from a feature called a Dual Stage Actuator. Drives with this feature include a drive arm (which moves the read/write head) with two joints, rather than the usual one. The benefit? More precise movement of the head delivers greater positional accuracy over the data tracks, leading to improved performance. Dual Stage Actuators were traditionally offered in expensive enterprise drives, but in recent years have found their way into certain consumer drives too.
Here’s another crazy feature name from Western Digital – NoTouch Ramp Load Technology. According to WD, in drives that include this feature, a plastic ramp secures the actuator in a specific position so that the heads always stay suspended in the air and never actually touch the platters surface. No touch translates into less wear and tear, and improved reliability. So there!
All of these power-efficient features sound fabulous – but will they impact performance?
NAS Hard Drive Benchmarks: Desktop Hard Drive Results
In my tests, I uncovered a few insights that I’ll share. Firstly, and this may come as no surprise to many, the absolute performance of your NAS or home server – expressed here in network file transfer rates or power consumption – depends more heavily on the processor, RAM and other hardware used in the device than the hard drives you select. Low specification hardware will not suddenly be transformed by slipping in a different hard drive, and neither will high specification hardware be compromised too greatly by using a green desktop drive over a standard drive or vice versa.
To use a car analogy, switch from standard tyres to racing tyres on your Ford Focus, and you’re still not going to beat that Ferrari in a straight line race. But you may go a little quicker than you would if you hadn’t changed them.
The Green drives did indeed deliver lower power consumption than standard desktop drives when compared at the device level – although again, the server hardware itself contributes greatly to the result. For example, the WD MyCloud Mirror pulls just 15 W under load using WD Blue 1 TB hard drives, while our Windows 8.1 machine needed 42 W with a 2 TB Green Drive array. However, switch from the hungriest standard desktop drive to a power sipping Green drive and power savings ranged from 15% to 25% across the test.
With regard to transfer performance, I expected to see the standard desktop drives easily outpace the low-power drives, but in fact the results were mixed across the devices. On a few of the servers – the QNAP TS-259 Pro+, the ASUSTOR AS-609RS and QNAP TS-451 I saw a small (2-8%) write speed gain from the slowest Green drive to the the fastest standard drive. On other devices, such as the Windows 8.1 “home server”, the WD Blue 1 TB desktop drive was actually slower than the WD Greens. A stronger trend was found when it came to read performance, with a 7-9% gain seen on the QNAP TS-259 Pro+, ASUSTOR AS-304T and AS-609RS.
So, in the desktop drive arena, the Green drives proved to do their job overall in reducing power consumption with only a minimal performance hit.
We step up from Desktop drives to a relatively new class of storage – NAS Hard Drives. Emerging in mid-2012, NAS drives ship with specialist firmware that tailors the operation to be more suitable for network attached storage devices. There are two big players in this sector – Seagate’s NAS hard drives and Western Digital’s Red series.
Seagate’s specialist firmware is called NASworks, and claims improved drive reliability courtesy of three core features. Error-recovery controls maintain the integrity of data stored in a RAID array. Typically, if a hard drive takes longer than seven seconds to acquire data (which could happen if the drive is attempting to recover data from a damaged sector), a NAS device will assume that the hard drive has fallen out of the array and will initiate a full rebuild of the array, which can take hours, if not days to complete. Unlike a standard desktop drive, Seagate’s NASworks firmware ensures the NAS hard drive stops tying to recover the data before those seven seconds have elapsed and will notify the RAID controller that it needs help recovering the data. Rather than initiate a full rebuild, the RAID controller should instead trying to recover the data from its redundant backup, saving the user the pain of impaired performance during a RAID rebuild.
The second feature included in Seagate’s NAS hard drives focuses on vibration. As you’d expect in a mechanical device, the high-speed platter rotation in desktop hard drives creates vibration – minute vibrations, but vibrations all the same. Those vibrations may not be a problem in a single drive desktop PC, for example, but in a multi-bay NAS device, the effect can be amplified and, according to the hard drive manufacturers, can impair performance as a result. So, Seagate include a feature called Dual-Plane Balance which balances the hard drive motor, minimising vibration. In Seagate drives, this feature works best for NAS devices with up to five bays – the company recommends Enterprise drives, with additional features to manage vibration, in larger devices.
Finally, let’s talk Power Management. Standard Desktop drives are built with a power management profile to suit the working week – they’re not expected to be running 24/7. In Seagate’s NAS hard drives, the power management profile is tailored for 24/7 operation, with the necessary settings to go into the relevant sleep or standby mode when required. Seagate says that this reduces power consumption and improves drive reliability.
Over on the Western Digital side of the fence, WD Red hard drives tell a very similar story, albeit with slightly different words. Their NASware 3.0 firmware now supports devices up to eight bays (compared to Seagate’s five) with similar features. For NAS devices between eight and sixteen bays, a WD Red Pro range of drives is available and is also recommended for rackmount devices. 3D Active Balance Plus is the name given to WD’s dual-plane balance feature, for vibration control, available across WD’s 3.5″ Red hard drive range (2.5″ Red drives are also available but do not support this feature).
Like the Seagate NAS drives, similar error-recovery controls and 24/7 power management profiles are included in WD Red drives to improve operation and reliability. An additional data protection feature, Command Completion minimises the data corruption in the event of an unexpected power loss by completing the command in process before shutting down.
Western Digital claims greatly enhanced reliability for the NAS drives over standard desktop drives equating to a 35% MTBF improvement. MTBF? Mean Time Before Failure – no hard drive manufacturer can claim a drive will never breakdown, so from their testing, they have traditionally calculated an MTBF figure, outlining the amount of operating hours a drive will last, on average, before a failure. That said, while quoting MTBF improvements for WD Red drives, Western Digital says elsewhere on their website that they don’t calculate MTBF figures anymore, but rather quote drive reliability in Component Design Life (CDL) and Annualized Failure Rate (AFR). The Component Design Life of a WD drive is quoted at 5 years and the Annualized Failure Rate is less than 0.8%. Seagate too have moved away from MTBF and now quote AFR figures (at <1%) for their drives.
So, what NAS drives have we selected for our test? On the Seagate side, we have the Seagate NAS 4 TB hard drive (ST4000VN000). At the time of writing, it’s the highest capacity NAS drive available from Seagate. From Western Digital, we have two generations of NAS hard drive. The 2 TB WD Red (WD20EFRX) running NASworks 2.0 as well as the latest generation of WD drives, the 6 TB WD Red (WD60EFRX) with NASworks 3.0. Both WD drives have a quoted MTBF of 1,000,000 hours (yes, I know they said they don’t calculate MTBF anymore, but it’s stated on their marketing materials!)
NAS Hard Drive Benchmarks: NAS Hard Drive Results
While there are only a few NAS drives on the market at the moment, this was a great chance to see how Seagate and Western Digital’s NAS drives stacked up against one another. Reasonably similar features, reasonable similar hardware should equate to reasonably similar results. Right? Actually, I found some notable differences. The first comparison was on power consumption – an almost universal trend saw higher power consumption from the Seagate 4 TB NAS drives than either of the Western Digital drives, which was a surprise. OK, we were testing drives of varying capacities – 4 TB Seagate drives vs 2 TB and 4 TB WD drives, but power consumption was not proportional to capacity.