by Hugh Barros
02/13/2013 | 02:09 AM
In the summer of 2012 Western Digital unveiled its Red product series optimized for network attached storage devices. It is positioned by the manufacturer as optimal for entry-level and midrange NASes that can take in 1 to 5 HDDs. Corporate users are offered the WD RE series instead.
We might have expected a special series of NAS-optimized hard disk drives to come out sooner or later. Although WD’s Green HDDs are quite appropriate for this scenario, they, like most desktop HDDs, lack NAS-specific optimizations. The manufacturer mentions the following requirements to HDDs designed for NASes: 24/7 operation, optimizations for fault-tolerant RAIDs (error correction algorithms), multiple HDDs in a single housing (temperature, vibration). Unfortunately, most of these parameters are hard to check out in practice, so we have to trust the manufacturer that the firmware and design of the Red series is different indeed. We’ll limit ourselves to those parameters that we can study, such as data-transfer speed.
The Red series includes products with a storage capacity of 1, 2 and 3 TB. All of them have SATA 6 Gbps interface and 64 MB of cache. We’ve got 2TB products from three series for our today’s tests: WD Green WD20EARX, WD RE4-GP WD2002FYPS and WD Red WD20EFRX. Using full-featured WD RE drives instead of their energy-efficient counterparts seems to be overkill for home NASes, though, especially as such enterprise-class HDDs are considerably more expensive. We should also note that the Green and RE4-GP series have been around for a few years already, which is quite a long time for the dynamic IT market.
The manufacturer doesn’t specify the MTBF parameter for the Green series, but 750,000 hours has been mentioned earlier. For the RE4-GP and Red series the MTBF is specified to be 1,200,000 and 1,000,000 hours, respectively. The Green can last through 300,000 load/unload cycles whereas the other series are twice as durable. The Red features a higher operating temperature (up to 70°C) while the vibrations requirements are identical across all the series. All of them have IntelliPower in their specified rotation speed but that parameter is unimportant for home users.
From a practical point of view, the warranty period is much more important and the Green, RE4-GP and Red come with a 2-, 5- and 3-year warranty, respectively. In our tests we will check out their speed, power consumption and temperature in a high-quality 4-disk NAS.
The NAS is Synology’s DS412+ model with DSM 4.1 version 2668 firmware. It is one of the fastest NASes based on the Intel Atom platform. The client device is an Intel Core i5 PC running 64-bit Windows 7. The PC’s network card is connected directly to the NAS. Jumbo Frames technology is enabled.
For the first group of tests we used Intel NASPT with modified HD video processing templates (the size of files was increased to 8 GB). We also added random read and write templates. File operations undergo a few stages of caching, which affects the resulting speed. To reduce this effect, we installed a rather small amount of system memory on the client PC – 2 gigabytes.
The first diagram shows how the HDDs perform in a JBOD. In reality, considering the size of the files and HDDs, the first disk of the array was doing the bulk of work.
The difference in firmware is obvious from the first three templates. The RE4-GP can only recognize the single-threaded reading template. The Green copes with two data threads and the Red can identify as many as four. That’s good for a home system. The simultaneous reading and writing is yet another scenario where we can see the HDDs differ: the Red is about 10% faster. It also enjoys a 40% advantage in random writing. The other components of our configuration being the same, it is the HDD that takes all the praise.
RAID0 smoothes out the differences between the HDDs. We can only note that the Green is somewhat slower than the others at reading whereas the Red is faster at random writing.
The RE4-GP wins the test of sequential reading and writing in the fault-tolerant RAID5 configuration but the Red series isn’t far behind and goes ahead at random writing. The Green isn’t very good at reading four data threads, but has no catastrophic performance hits.
RAID6 isn’t a popular option for home 4-disk NASes but it is with this RAID type that the RE4-GP enjoys an advantage over the other HDDs in sequential reading. All of them have identical results at sequential writing but the Red is ahead at random writing.
The new WD Red series is often faster than its opponents when it comes to the classic NAS usage scenario, i.e. LAN-based data access. It enjoys the largest advantage in the random read template. It may be due to some special optimizations for NAS applications or just improvements in WD’s firmware, but the Red series is really better than the Green series in terms of sheer speed. Let’s check out the other parameters now.
To measure the power consumption of our HDDs we used a special testbed capable of monitoring electric currents on the 5 and 12V power rails. We measure average consumption in different modes: idle, random reading/writing and sequential reading/writing. The HDDs run IOMeter in this test.
The RE4-GP series was expected to be the most voracious in this test but we must admit that up to 8 watts per one HDD isn’t very much. As for the Green and the Red, the former has the lowest idle power draw of less than 2 watts, but when there is some kind of disk load, the Red is more economical. Power adapters of modern NASes will surely be able to deliver the required amount of juice. Let’s just check out the startup currents.
There’s no reason to worry here, considering that the HDDs usually start up one by one rather than all together.
The low power consumption has a positive effect on temperature. So, we checked out our HDDs using the NAS’s integrated monitoring system while running Intel NASPT on RAID5 arrays built out of four HDDs. The ambient temperature was about 22°C. We must admit that the results cannot be compared directly because the NAS has an active cooling system with an automatically regulated fan. We couldn’t monitor the fan’s rotation speed.
Anyway, we shouldn’t worry about temperature as it only peaked to 36°C. The WD Red series drives are somewhat colder than their cousins on average. This may be the reason why the system temperature was higher: the NAS’s fan worked at a reduced speed when we installed the Red drives.
Western Digital’s Red series is definitely a success. It is superior to its predecessor in those parameters we could measure in our tests such as speed, power consumption and temperature. This advantage may be due to the progress that has been made in developing and manufacturing HDDs but the NAS-oriented firmware optimizations also contribute to its high performance, especially at writing. Talking about 4-disk NASes, their performance is actually limited by the Gigabit Ethernet interface rather than by the hardware platform or HDDs, so further progress can only be achieved in terms of lower power consumption and firmware optimizations for NAS-specific loads.
As we wrote above, it’s impossible to check out such an important parameter as reliability during a brief test session. But it is indicated by the warranty provided by the manufacturer (the MTBF parameter is synthetic and doesn’t reflect a drive’s reliability well enough).
So, the WD Red is surely a good choice for NASes. You only have to make sure that it is on the NAS’s compatibility list. Most NAS makers have already tested the Red series for such compatibility with their products. On the other hand, if you’ve already got a working NAS with WD Green drives, you shouldn’t hurry to upgrade unless you want to expand your storage capacity.
As for the price factor, the new series is currently slightly more expensive than the WD Green but much cheaper than the WD Black and RE series. Considering that the latter do not offer any significant advantages for NAS applications, the Red is obviously a better choice in this respect, too.