Review Index:

Western Digital Red 6TB and Red Pro 4TB Full Review - Bigger and Faster

Subject: Storage
Manufacturer: Western Digital
Tagged: wdc, WD, Red Pro, red, hdd, 6tb, 4TB

Introduction and Specs


*** NOTE ***

In the preparation for this review, we noted abnormal behavior with the 6TB Red. After coordination with Western Digital, they replicated our results and will be issuing a firmware to correct the issue. We are publishing this piece as-is, with caveats added as appropriate. We will revisit this piece with an additional update once we have retested the 6TB Red on the updated firmware / configuration. More information / detail is available in our related news post on this matter.

** Update ** WD corrected early shipments of these drives and we have a full retest of the corrected units posted here.

*** END NOTE ***

Last year we covered the benefits of TLER enabled drives, and the potential for drive errors in a RAID can lead to the potential loss of entire arrays. Western Digital solved this problem by their introduction of the WD Red series. That series was since incrementally updated to include a 4TB capacity, and other Western Digital lines were also scaled up to 4TB capacities.

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This week the Red line was updated to include both 5TB and 6TB models, sporting 1.2TB per platter. Performance is expected to be slightly improved over the older / smaller capacities of the Red. The upgraded line will use an improved 'NASware 3.0' firmware, which makes improvements to Western Digital's software based vibration compensation. These improvements mean WD can now support up to 8 Reds in a single chassis (up from 5 with NASware 2.0).

Also announced was the new Red Pro line, available in capacities up to 4TB. The Red Pro is just as it sounds - a 'Pro' version of the Red. This model borrows more features from WD's enterprise line, making it very similar to an SE series HDD. Imagine a Red, but at 7200RPM and more aggressive seek times. The Red Pro also borrows the enterprise-grade 5-year warranty and is supported in chassis up to 16 bays, thanks to built-in hardware vibration compensation. When all is said and done, the Red Pro is basically a WD SE with firmware tweaked for NAS workloads.

As a recap of what can potentially happen if you have a large RAID with 'normal' consumer grade HDD's (and by consumer grade I mean those without any form of Time Limited Error Recovery, or TLER for short):

  • Array starts off operating as normal, but drive 3 has a bad sector that cropped up a few months back. This has gone unnoticed because the bad sector was part of a rarely accessed file.
  • During operation, drive 1 encounters a new bad sector.
  • Since drive 1 is a consumer drive it goes into a retry loop, repeatedly attempting to read and correct the bad sector.
  • The RAID controller exceeds its timeout threshold waiting on drive 1 and marks it offline.
  • Array is now in degraded status with drive 1 marked as failed.
  • User replaces drive 1. RAID controller initiates rebuild using parity data from the other drives.
  • During rebuild, RAID controller encounters the bad sector on drive 3.
  • Since drive 3 is a consumer drive it goes into a retry loop, repeatedly attempting to read and correct the bad sector.
  • The RAID controller exceeds its timeout threshold waiting on drive 3 and marks it offline.
  • Rebuild fails.
  • Blamo, your data is now (mostly) inaccessible.

I went into much further detail on this back in the intro to the WD 3TB Red piece, but the short of it is that you absolutely should use a HDD intended for RAID when building one.

Continue reading our review of the new WD 6TB Red and 4TB Red Pro!!


First the slide from WD's brief on the new Reds:

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Here's my translation of Western Digital's marketing speak for the specs of the WD Red Series. Some of these are not specifically listed by WD, but we know they are in there, so we will keep them here for your education:  

  • NoTouch™ ramp load technology — Previously called "IntelliPark".  Drive heads take an 'exit ramp' off of the platters instead of landing on the platters when the drive is spun down.  You know how the most damage is done to your engine when you start it on a cold morning?  This means the drive heads do not have to break stiction each and every time the drive spins up.  The heads are able to leave the ramp and float onto the spinning disk.  
  • Native Command Queuing (NCQ) — The drive can reorder groups of reads/writes to minimize overall head movement, and therefore increase effective access time.  Beware - this is only effective with an AHCI-enabled SATA controller.  
  • Perpendicular Magnetic Recording (PMR) — Bits are aligned vertically instead of horizontally to get more packed onto each platter.  Think dominoes (the game, not the food).
  • 64MB cache — Basically standard across most current WD models, though this part is faster than those previous.  Increased cache speed helps boost random access performance.  
  • Dual processors — Introduced with the RE4-GP line, the additional core helps the drive keep track of the added cache and increased throughput streaming off of the head pack.
  • Advanced Format — Introduced back in late 2009, this increases storage efficiency and robustness by having the drive handle data as 4KB internal blocks. This means error correction routines are not limited to 512B segments. ECC works better on larger chunks of data, and this gives an ~50% improvement in that area. The trade-off is random access for blocks <4KB will suffer, but this is not much of an issue as the vast majority of file access is >= 4KB.
  • RAID-specific time-limited error recovery (TLER) — The drive limits the 'hang' experienced on a read error in order to avoid a RAID controller considering the drive dead / offline.
  • Rotary Acceleration Feed Forward (RAFF™) — The addition of a pair of hardware accelerometers to enterprise (and Red Pro) drives. These sensors feed back vibration information to the controller, which can then correct for those vibrations by offsetting the head servo accordingly. The end result is that performance remains more consistent in the presence of chassis vibrations.
  • 3D Active Balance Plus — Our enhanced dual-plane balance control technology significantly improves the overall drive performance and reliability. Hard drives that are not properly balanced may cause excessive vibration and noise in a multi-drive system, reduce the hard drive life span, and degrade the performance over time.
  • NASware — A collection of firmware enhancements applied to Red series drives. These features include:
    • Reliability — NASware firmware is intended for 24/7 usage (as opposed to typical desktop consumer drive usage patterns).
    • Compatibility — Additional tweaks are made to ensure compatibility with various NAS units.
    • Power Measures — Red series drives can more easily handle power fluctuations seen in some NAS devices, enabling them to spin up and power down in the presence of voltage dips and spikes which might occur due to a limited supply of power available to the NAS. This is more likely on a home NAS, as they use power bricks and not full PC power supplies.
    • Software-based vibration compensation — This is a software implementation of the RAFF feature detailed above. The difference is that instead of accelerometers, the sensing mechanism comes from feedback from the tracking information seen at the drive head. basically, if vibration causes the head to shift, that shift can be detected by the head itself (track data), and that can then be fed back and corrected in software by the controller. It's not as good as hardware-based RAFF, but it is better than not having it at all, and it enables the Red to be rated at 8 drives in a single enclosure.

The load/unload spec (for the ramp load technology) remains at 600,000 cycles.

July 24, 2014 | 01:49 AM - Posted by Anonymous (not verified)

I am a capitalist. I do not use red drives!!! lol!

July 24, 2014 | 08:50 AM - Posted by Anonymous (not verified)

Then buy a purple drive, you fairy :-P

July 24, 2014 | 11:03 AM - Posted by BBMan (not verified)

If you ain't black, you ain't crap.

July 25, 2014 | 11:58 AM - Posted by Anonymous (not verified)

Don't be mean, buy Green.

July 24, 2014 | 10:19 AM - Posted by Patrick3D (not verified)

Good to know these are affordable. I've still got about a year before I run out of space using 4TB REDs, then I'll start upgrading with 6TB drives. I tried Seagate's NAS drives but the one's I bought (at least) were way too loud for use at home.

July 24, 2014 | 11:45 AM - Posted by SilverBullet (not verified)

3TB is still the best $/GB at $0.043/GB. Better density for the NAS drives, though not sure the price is worth it.

July 25, 2014 | 12:00 PM - Posted by Anonymous (not verified)

No. 5TB Seagate externals are $190. $0.038/GB. I can't buy them fast enough!

July 26, 2014 | 02:22 PM - Posted by IanW (not verified)

I think your failure premise is a bit contrived. No one should be running a RAID system of any type without full SMART checks on a regular basis at the very least.

July 28, 2014 | 09:35 AM - Posted by Allyn Malventano

I've personally had RAIDs fail in that scenario even with SMART checks in place, as well as weekly full array data scrubs. Fact is that unless you have some form of TLER, a second drive failure that occurs mid rebuild will cause most RAID controllers to offline the array.

Ryan had also had such a failure (using Seagate drives), and I had to recover his array by imaging the non-failed drives and manually de-striping in software.

August 2, 2014 | 12:55 AM - Posted by Anonymous (not verified)

Curious Allyn, which imaging software did you use to rescue that array ???

August 26, 2014 | 12:53 PM - Posted by Allyn Malventano

It wasn't the imaging software that did the rescue - all it did was create images of the drives (and read past the unreadable areas after hours of timeouts / retries). One I had the images, I coded something myself to re-stitch, using alternating parity (i.e. two drives had unreadable sectors in (mostly) alternating areas relative to each other).

That was for my array recovery. Ryan's was easier, as he had just one drive with a small cluster of bad sectors causing his array to timeout. I was able to image that drive and re-stitch that array back together with a tool from Runtime Software - but with some custom settings I had to come up with myself, as Ryan's array was not easy for that software to 'lock' onto in auto mode.

July 27, 2014 | 02:09 AM - Posted by Anonymous2 (not verified)

So the pro is "better" & expected to last longer, yet is 6dBA LOUDER than the standard WD RED....

Also, did anyone else notice they changed the "Non-recoverable read errors per bits" to look better despite being the same?

July 28, 2014 | 09:37 AM - Posted by Allyn Malventano

It's a 7200 RPM enterprise spec drive. *Of course* it is faster / louder.

July 28, 2014 | 07:52 AM - Posted by Anonymous (not verified)

You should look into how Seagate is intentionally crippling consumer HDDs with low APM states and special firmware to scare enterprise customers into buying more expensive drives.

July 28, 2014 | 12:01 PM - Posted by Josh9000 (not verified)

Can we mix and match Green and Red drives?

November 8, 2014 | 11:46 AM - Posted by Bianca (not verified)

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December 15, 2014 | 11:43 AM - Posted by Anonymous (not verified)

Hi I've got 3 existing 1year old WD RED 4TB drives and am moving to a new Synology 1515plus. I'd like to expand my storage and am considering a RED PRO instead of buying another standard 4TB RED drive
My question is this, is it bad to mix a new 4TB RED PRO with the older 4TB standard RED drives in a RAID?

Thanks in advance

December 17, 2014 | 04:24 AM - Posted by John B (not verified)

I have almost the same question, except i have 5 x one year old wd red 3tb's and am expanding to 8 drives...Would it be better to use 3 new pro drives, or stick with 3 new standard red drives?

Thanks in advance.

oh, and by the way.....Merry Christmas to all on here!

February 26, 2015 | 11:21 AM - Posted by Anonymous (not verified)

Pro drives would be your best bet, since they have accelerometers in like the Se drives to actively reduce vibration. Though even the newer plain reds have nasware 3.0 and so have software based vibration reduction, allowing upto 8 drives.

WD have also said they will honour warranties of those using older (1-5 bay drives) in 8 bay configs.

Perhaps on cost, plain reds would be better, don't forget the red pro isn't a home NAS drive, it's louder, faster, and uses more power (around 5w/drive more), designed for heavier use.

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