Feature Set Comparison

Enterprise hard drives come with features such as real time linear and rotational vibration correction, dual actuators to improve head positional accuracy, multi-axis shock sensors to detect and compensate for shock events and dynamic fly-height technology for increasing data access reliability. These hard drives also expose some of their interesting firmware aspects through their SATA controller, but, before looking into those, let us compare the specifications of the ten drives being considered today. Even though most of the data for all ten drives is available below, readers can view only two at a time side-by-side due to usability issues.

Comparative HDD Specifications
Model Number WD4001FFSX WD4001FFSX
Interface SATA 6 Gbps SATA 6 Gbps
Sector Size / AF 512E 512E
Rotational Speed 7200 RPM 7200 RPM
Cache 64 MB 64 MB
Rated Load / Unload Cycles 600 K 600 K
Non-Recoverable Read Errors / Bits Read < 1 in 1014 < 1 in 1014
MTBF 1 M 1 M
Rated Workload ~ 180 TB/yr ~ 180 TB/yr
Operating Temperature Range 5 to 60 C 5 to 60 C
Acoustics (Seek Average - dBA) 34 dBA 34 dBA
Physical Parameters 14.7 x 10.16 x 2.61 cm, 750 g 14.7 x 10.16 x 2.61 cm, 750 g
Warranty 5 years 5 years
Price (in USD, as-on-date) $260 $260

A high level overview of the various supported SATA features is provided by HD Tune Pro.

A brief description of some of the SATA features is provided below:

  • S.M.A.R.T: Most readers are familiar with the SMART (Self-Monitoring, Analysis and Reporting Technology) feature, which provides drive parameters that can server as reliability indicators. Some of these include the reallocated sector count (indication of bad blocks), spin retry count (indication of problems with the spindle motors), command timeout (indication of issues with the power supply or data cable), temperature, power-on hours etc.
  • 48-bit Address: The first ATA standard specified 24 bits for the logical block address (sector), which was later updated to 28 bits. Using 28 bits, one could address up to 137.4 GB (2^28 * 2^9 bytes), which capped the SATA drive size. In 2003, an update to the standard was released to allow 48 bits for the LBA address to get past this issue. No modern SATA drive comes without support for 48-bit addresses.
  • Read Look-Ahead: Drives supporting this feature keep reading ahead even after the current command is completed. The data is transferred to the buffer for faster response to the host in the case of sequential accesses.
  • Write Cache: This feature is pretty much self-explanatory, with data being stored in the buffers prior to being committed to the platters. There is a risk of data loss due to power loss. The feature can be disabled by the end user.
  • Host Protected Area (HPA): Drives supporting this feature have some sectors hidden from the OS. It is usually used by manufacturers to store recovery data, but users can also 'hide' data by allocating sectors to the HPA.
  • Device Configuration Overlay (DCO): Drives supporting this feature can report modified drive parameters to the host.
  • Security Mode: Drives supporting this feature can help protect themselves from illegal accesses or setting of new passwords (by freezing such functions). Readers might have encountered frozen security settings for SSDs while trying to secure erase them..
  • Automatic Acoustic Management: AAM was declared obsolete in the 2010 ATA standards revision. On supported disks, it enables reduction of noise that rise from fast spin-ups of the disk. In general, configure the AAM value to something low would result in a quiet, but slow, disk, while a high value would result in a loud, but fast, disk.
  • Power Management: Support for this feature enables drives to follow specific power management state transitions via commands from the host. Supported modes include IDLE, SLEEP and STANDBY.
  • Advanced Power Management (APM): This feature allows setting of a value to allow for disk spindowns as well as adjustment of head-parking frequency. Some disks have proprietary commands for achieving this functionality (for example, the WDIDLE tool from Western Digital can be used with the Green drives).
  • Interface Power Management: Drives supporting this feature allow for fine-tuning of power consumption by being aware of various interface power modes such as PHY Ready, Partial and Slumber (in the order of power consumption). Transitions from a higher power mode to a lower one usually happen after some period of inactivity. They can be either host-initiated (HIPM) or device-initiated (DIPM). Note that these refer to the SATA interface and not the device itself. As such, they are complementary to the power management feature mentioned earlier.
  • Power-up in Standby: This SATA feature allows drives to be powered up into the Standby state to minimize inrush current at power-up and allow the host to sequence the spin-up of devices. This is particularly useful for NAS units and RAID environments. Desktop drives usually come with power management disabled, but there are jumper settings on the drive to enable controlled spin-up via ATA standard spinup commands. For drives targeting NAS units, power Power-up in Standby is enabled by default.
  • SCT Tables: The SMART Command Transport (SCT) tables feature extends the SMART protocol and provides additional information about the drive when requested by the host.
  • Native Command Queuing (NCQ):  This is an extension to the SATA protocol to allow drives to reorder the received commands for more optimal operation.
  • TRIM: This is a well known feature for readers familiar with SSDs. It is not relevant to any of the drives being discussed today.

We get a better idea of the supported features using FinalWire's AIDA64 system report. The table below summarizes the extra information generated by AIDA64 (that is not already provided by HD Tune Pro).

Comparative HDD Features
DMA Setup Auto-Activate Supported, Disabled Supported, Disabled
Extended Power Conditions Supported, Disabled Supported, Disabled
Free-Fall Control Not Supported Not Supported
General Purpose Logging Supported, Enabled Supported, Enabled
In-Order Data Delivery Not Supported Not Supported
NCQ Priority Information Supported Supported
Phy Event Counters Supported Supported
Release Interrupt Not Supported Not Supported
Sense Data Reporting Not Supported Not Supported
Software Settings Preservation Supported, Enabled Supported, Enabled
Streaming Supported, Disabled Supported, Disabled
Tagged Command Queuing Not Supported Not Supported
4 TB NAS and Nearline Drives Face-Off: The Contenders Performance - Raw Drives


View All Comments

  • willis936 - Friday, August 8, 2014 - link

    Thank you for the overview of ATA protocol features on page 3. Resources like that are hard to find without spending hours digging through a spec. Reply
  • Anonymous Blowhard - Friday, August 8, 2014 - link

    "Enterprise" or not, running RAID5 on 4TB drives with a 10^14 URE is asking for trouble. Reply
  • Guspaz - Friday, August 8, 2014 - link

    Only when rebuilding. The chances of getting a read error on two disks at the same time on the same piece of data is extremely remote. Of course, when rebuilding, you only need the error on one disk... which is why I'm running raidz2 :) Reply
  • rufuselder - Thursday, October 9, 2014 - link

    I'd say WD AV-GP 2 TB AV is the best choice (supported by for example http://www.consumertop.com/best-computer-storage-g... ). I'm not a big fan of raidz2, sorry. Reply
  • NonSequitor - Friday, August 8, 2014 - link

    This came up on the last article about these drives as well. Currently I'm running six 3TB Reds in a RAID-6. Over the last year they've rebuilt once a month. I have Linux set to log any errors, and it's never logged a single block error. With the double parity, it seems like it would have logged one by now if the actual URE were that high on a per-bit basis. This unit was a replacement for a unit using nine drives, which did have two drive failures in three years, but both failures were announced by SMART before any actual failure occurred. The SANs at work do scrubs once a week, and kick out about 2% of drives a year. It really seems like reality is better than the specifications in this case. Reply
  • jaden24 - Friday, August 8, 2014 - link

    Why are they rebuilding once a month? Reply
  • NonSequitor - Friday, August 8, 2014 - link

    I have it set that way to spot a failing drive before it actually needs to be rebuilt. It's an orderly rebuild, checkarray, like this: http://www.thomas-krenn.com/en/wiki/Mdadm_checkarr...
    In the past it has been useful as it has caused drives to throw a SMART error for reallocates during the process (with some 1TB drives) allowing me to replace them proactively.
  • jaden24 - Saturday, August 9, 2014 - link

    Interesting. I had never heard of the practice before. Only consistent scrubbing, SMART configured, and extended burn-ins prior to use. Reply
  • imaheadcase - Friday, August 8, 2014 - link

    Ganesh, could you get a response from Synology/asus/Qnap/etc as to why they don't have NAS with better CPU/RAM? Those products are nice, but many people wish to have them with more CPU/ram for media streaming. I find it very odd than none of the major players don't contribute to this market.

    Why no 3ghz CPU and 16gig systems? It can't be cost since the ones that can be upgraded ram wise are cheap upgrades.

    Out of the current popular NAS, only 2 support Transcoding, and multiple 1080p streams. But they have terrible software.
  • Gigaplex - Monday, August 11, 2014 - link

    You don't need a 3GHz CPU, 16GB RAM NAS to support media streaming. Reply

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