HGST Ultrastar 7K4000 Enterprise HDD Review

Introduction

The HGST Ultrastar 7K4000 (HUS724040ALS64) is a SAS 3.5" 7,200 RPM HDD in a traditional 3.5" form factor. The 7K4000 is geared for a multitude of uses in the datacenter, from NAS, RAID, disk-to-disk backup and replication, to cloud storage an Massive Scale Out (MSO) architectures. The 7K4000 comes in capacities of 2TB, 3TB and 4TB.

The 7K4000 is also available in both 6Gb/s SAS and SATA versions, allowing administrators to adjust to the service level required for their individual environments. The SAS interface provides HA (High Availability) features such as failover and multipath, and the more robust feature SAS feature set.

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An HDD designed for such a wide range of applications has to offer large capacity, fast consistent performance and a low power threshold to minimize long term TCO. The HGST 7K4000 has a number of features that make it particularly well suited for these applications, beginning with speed.

The SAS version of the 7K4000 we are testing offers up a sustained data transfer rate of 172 MB/s, while the SATA models feature speeds of 171/181 MB/s depending upon the capacity point. The 7K4000 also touts a seek time of 8.0ms delivered via five 800GB platters, an increase of 33% more capacity from the previous 7K3000. Both SAS and SATA drives feature 64MB of cache, though the SAS version uses 512/520/528 sector sizes in comparison to the SATA model with its 4K Advanced Format and 512 byte emulation (512e) and legacy format (512n).

The 7K4000 also features great power consumption characteristics, with 24% lower Watts per GB than the 3TB Ultrastar 7K 3000 predecessor. The focus on power efficiency has spawned five Advanced Power Management modes, which create a 59% reduction in power consumption in comparison to the peak output and can pull a less than 1 Watt total in standby and sleep modes.

After we look at speeds and feeds, the eye turns to reliability, and the 7K4000 does not disappoint. It is designed for 600,000 load/unload cycles and 24x7 usage in multi-drive environments, and to combat the high vibration in server racks, the drives utilize a Dual Stage Actuator (DAS) and Enhanced Rotational Vibration Safeguard (RVS). These enhanced technologies play a part in a standard 1 in 10^15 non-recoverable read bit error rate. The real meat of the reliability picture comes from the whopping 2,000,000 hour MTBF rating. This is nearly double the MTBF of other HDDs in this class, including those used for comparison in our performance testing. This tremendous MTBF results in an AFR (Annualized Failure Rate) reduction of 40%.

Rounding this impressive feature set out with optional TCG Enterprise-A encryption for the SAS models creates a solid, well-rounded product backed by an industry leading five year warranty.

HGST Ultrastar 7K4000 Specifications

The HGST Ultrastar 7K4000 provides an average seek latency of 8.0ms and a sustained transfer rate of 172 MB/s for the SAS model, and 181/172 MB/s for the SATA models. This is delivered via a 6Gb/s connection and a 7,200 RPM speed. The Ultrastar 7K4000 series of HDDs comes in a standard 3.5" form factor.

For typical workloads, the drive pulls an average of 11.4 watts for read/write workloads, 6.9 Watts at idle and 5.7 Watts unload idle. Advanced Power Management allows five different modes to customize power characteristics. Some sleep and standby states pull as low as 1 Watt, creating a great option for cold data storage and replication environments.

The HGST naming convention can be a bit daunting for those unaccustomed to the nomenclature, but the specification sheet above has a handy decoder to the left of the chart. Models with encryption capabilities feature Bulk Data Encryption for SATA models and TCG Enterprise_A for SAS.

HGST has certified the Ultrastar 7K4000 as an EcoTrac design, denoting a halogen-free design and power inefficient operation.

The MTBF is rating pops out at a whopping two million hours, and there is a load/unload rating of 600,000 cycles. The HUS724040ALS64 series of HDDs is designed for an always-on usage model and is backed by a five year warranty.

HGST Ultrastar 7K4000 Internals

The HGST Ultrastar 7K4000 comes in a standard 3.5-inch form factor.

Removing the PCB reveals the foam pad used to dampen vibration during use. We can observe the single thermal pad used for the drive controller.

The Winbond is a 64MB DDR2 component for caching, a Smooth chip to control the drive motor, and an LSI drive controller.

The SAS 6Gb/s connection allows for a robust instruction set, dual port and failover technologies.

Test System and Methodology

We utilize a new approach to HDD and SSD storage testing for our Enterprise Test Bench, designed specifically to target long-term performance with a high level of granularity.

Many testing methods record peak and average measurements during the test period. These average values give a basic understanding of performance, but fall short in providing the clearest view possible of I/O QoS (Quality of Service).

'Average' results do little to indicate the performance variability experienced during actual deployment. The degree of variability is especially pertinent, as many applications can hang or lag as they wait for I/O requests to complete. This testing methodology illustrates performance variability, and includes average measurements, during the measurement window.

While under load, all storage solutions deliver variable levels of performance. While this fluctuation is normal, the degree of variability is what separates enterprise storage solutions from typical client-side hardware. Providing ongoing measurements from our workloads with one-second reporting intervals illustrates product differentiation in relation to I/O QOS. Scatter charts give readers a basic understanding of I/O latency distribution without directly observing numerous graphs.

Consistent latency is the goal of every storage solution, and measurements such as Maximum Latency only illuminate the single longest I/O received during testing. This can be misleading, as a single 'outlying I/O' can skew the view of an otherwise superb solution. Standard Deviation measurements consider latency distribution, but do not always effectively illustrate I/O distribution with enough granularity to provide a clear picture of system performance. We use histograms to illuminate the latency of every single I/O issued during our test runs.

We measure power consumption during test runs. This provides measurements in time-based fashion, with results every second, to illuminate the behavior of power consumption in steady state conditions. Power consumption can cost more over the life of the device than the initial acquisition price of the hardware itself. This significantly affects the TCO of the storage solution. We also present IOPS-to-Watts measurements to highlight the efficiency of the storage solution.

We conduct our tests over the full LBA range to allow each HDD to highlight its average performance. Short stroking can increase performance at the loss of capacity. The first page of results will provide the 'key' to understanding and interpreting our new test methodology.

4K Random Read/Write

Each QD for every parameter tested includes 300 data points (five minutes of one second reports) to illustrate the degree of performance variability. The line for each QD represents the average speed reported during the five-minute interval.

4K random speed measurements are an important metric when comparing drive performance, as the hardest type of file access for any storage solution to master is small-file random. One of the most sought-after performance specifications, 4K random performance is a heavily marketed figure.

The HGST Ultrastar 7k4000 flies high with the heavy read workloads with an average of 216 IOPS at QD256, a great start that sets the tone for the majority of our tests.

The HGST Ultrastar 7K4000 rises above in this test by averaging 211 IOPS and beating the competition. The Toshiba MG03ACA400 averages 199 IOPS in comparison to the Seagate V.6 with 205 IOPS at QD256 in our 4K write testing.

Our write percentage testing illustrates the varying performance of each solution with mixed workloads. The 100% column to the right is a pure write workload of the 4K file size, and 0% represents a pure 4K read workload.

The 7K4000 manages to beat both of the other 7,200 RPM HDDs with its mixed read/write workload performance across the board. This is stellar performance in mixed read/write workloads.

The HGST 7K4000 best the competition by providing 33,009 I/O's (53.92%) at 100-200ms, and 15,250 I/O's (24.19) in the 200-400ms range. The 7K4000 provides a mixed bag, with a higher distribution of I/O falling into the less desirable 200-400ms range than the competitors, but also a very good showing with the latency range dropping as low as 4-6ms.

We record the power consumption measurements during our test run at QD256. The HGST 7K4000 pulls a frugal 8.48 Watts during the measurement window.

IOPS to Watts measurements are generated from data recorded during our test. The HGST HDD delivers an average of 24.4 IOPS per Watt for 4K random writes, and 23 IOPS per Watt for 4K random read access.

8K Random Read/Write

8K random read and write speed is a metric that is not tested for consumer use, but for enterprise environments this is an important aspect of performance. With several different workloads relying heavily upon 8K performance, we include this as a standard with each evaluation. Many of our Server Emulations below will also test 8K performance with various mixed read/write workloads.

The HGST Ultrastar 7K4000 delivers an average of 215 IOPS at QD256, easily rising above its competitors.

The average 8K random write speed of the HGST HDD is 211 IOPS at QD256. The Seagate Enterprise Capacity V.6 averages 199 IOPS, followed by the Toshiba MG03ACA400 at 196 IOPS. The 7K4000 easily wins this test.

The 7K4000 again masters the mixed read/write testing with a solid lead over competitors.

Once again, we observe the disparate latency distribution, with 54.13% of I/O's (33,202) at 100-200ms, and 15,083 I/O's (24.59%) at 200-400ms, and a broad smattering of I/O's falling into the more desirable ranges.

Power consumption for the HGST 7K4000 averages 9.61 Watts during the test period.

The 7K4000 averages 21 IOPS per Watt in 8K random write, and 21 IOPS per Watt for 8K random read access. This excellent showing outstrips the competing solutions by a decent margin.

128K Sequential Read/Write

The 128K sequential speeds reflect the maximum sequential throughput of the HDD using a realistic file size encountered in an enterprise scenario.

The HGST Ultrastar 7K4000 averages 172 MB/s at sequential read speeds, following the Seagate with 178 MB/s and beating the Toshiba with its 163 MB/s.

The 7K4000 HDD averages 173 MB/s in sequential write speed, while the Seagate averages 175 MB/s and the Toshiba averages 162 MB/s.

The 7K4000 again posts excellent performance in our mixed read/write testing, easily leading in this test.

The HGST 7K4000 offers up 79.47% of requests in the 20-40ms range and 20.52% at 6-8ms. This great performance illustrates the strength of the 7K4000 with sequential data access.

The HGST 7K4000 averages 8.39 Watts during sequential write testing, besting the other HDDs.

The 7K4000 provides an average of 20 MB/s per Watt for 128K sequential write and 20 MB/s per Watt for sequential read.

Database/OLTP and Webserver

Database/OLTP

This test emulates Database and On-Line Transaction Processing (OLTP) workloads. OLTP is in essence the processing of transactions such as credit cards and high frequency trading in the financial sector. Enterprise HDDs are uniquely well suited for the financial sector with their low latency and high random workload performance. Databases are the bread and butter of many enterprise deployments. These are demanding 8K random workloads with a 66% read and 33% write distribution that can bring even the highest performing solutions down to earth.

The HGST Ultrastar 7K4000 flexes its mixed workload muscle and averages 225 IOPS at QD256.

The HGST 7K4000 offers up a wide range of access time, much like the other HDDs, but the latency distribution, while more consistent, falls into the higher ranges.

The HGST 7K4000 averages 9.58 Watts during the test period.

The HGST 7K4000 averages 22.7 IOPS per Watt in our Database/OLTP testing, once again leading the pack by a fair margin.

Webserver

The Webserver profile is a read-only test with a wide range of file sizes. Web servers are responsible for generating content for users to view over the internet, much like the very page you are reading. The speed of the underlying storage system has a massive impact on the speed and responsiveness of the server that is hosting the website, and thus the end-user experience.

The 7K4000 averages 212 IOPS at QD256.

The HGST 7K4000 again exhibits more consistent performance, albeit at a slightly higher latency range.

The 7K4000 averages 9.69 Watts during the test.

The HGST 7K4000 averages 21.4 IOPS per Watt during the measurement window, easily beating the competition.

Fileserver and Emailserver

Fileserver

The File Server profile represents typical file server workloads. This profile tests a wide variety of different file sizes simultaneously, with an 80% read and 20% write distribution.

The HGST Ultrastar 7K4000 averages 275 IOPS at QD256, easily beating the other competing solutions in this test.

The 7K4000 HDD averages 9.8 Watts during the test.

The HGST 7K4000 averages an impressive 27.4 IOPS per Watt during the measurement window.

Emailserver

The Emailserver profile is a very demanding 8K test with a 50% read and 50% write distribution. This application is indicative of the performance of the solution in heavy write workloads.

The HGST Ultrastar 7K4000 averages 221 IOPS at QD256.

The 7K4000 averages a miserly 9.19 Watts during the test.

The 7K4000 averages 23.5 IOPS per Watt.

Final Thoughts

HGST was formed in 2003 and became a wholly owned subsidiary of Western Digital in 2012. HGST still operates somewhat independently and maintains its U.S. headquarters in San Jose. While the two entities operate separately, HGST brings many benefits to the table and recent acquisitions of sTec and VeloBit have fallen under the HGST umbrella to solidify their existing market position in flash solutions. HGST also brings great HDD experience and expertise to the table, as evidenced by our test results of the Ultrastar 7K4000.

In our testing, the HGST Ultrastar 7K4000 excelled at all of our mixed read/write testing, easily besting the competition in these areas. Even in the more 'vanilla' pure read and write workloads, the HGST drive pulled ahead of the competition, posting leading results in the 4K and 8K random workloads.

In sequential data access, the HGST 7K4000 trailed the Seagate V.6 by a slim margin in our 128K sequential read/write testing, but the 7K4000 again dominated the mixed workload. In actual deployment, this class-leading performance in mixed read/write workloads will prove beneficial to the majority of workloads. This same performance led to excellent performance in our server emulations, which all feature mixed workloads.

Another bright spot for the 7K4000 came in our power testing. With frugal power consumption and excellent performance metrics, the 7K4000 exhibited superb IOPS to Watts performance metrics in the majority of our workloads. In our Email and Fileserver tests, the HGST Ultrastar 7K4000 provided simply dominating performance in comparison to other 3.5" 7,200 RPM HDD's.

The choice of five different Advanced Power Management modes also offers many opportunities for optimized power consumption, and the excellent sleep and standby power characteristics address a critical need in cold data storage environments. The impact of lower power consumption and higher performance per Watt on TCO simply cannot be overstated.

One area that the Ultrastar 7K4000 struggled in comparison to the other entrants was in latency measurements. In 100% write 4K and 8K random workloads, the HDD experienced a distribution that fell behind the competing HDDs. In our mixed workloads, the HGST 7K4000 provided a more consistent latency range, albeit at a higher range than the comparison HDD's.

Overall, there is a delicate balance of a number of factors to take into consideration. Reliability, performance, latency and power consumption are all factors to weigh when choosing the correct solution for the workload. With a five year warranty and a class-leading MTBF of two million hours, well above competing solutions, HGST Ultrastar 7K4000 easily cinches the reliability category.

It is not often that we have to adjust the scale of the charts higher for the same class of device to allow a new entry to 'fit' into the picture, but with the HGST Ultrastar 7K4000, we had to adjust both our performance and IOPS to Watts charts to accommodate the outstanding performance of the 7K4000. This is the signature of an excellent solution, and the excellent mixture of performance, power and reliability wins the HGST Ultrastar 7K4000 the TweakTown Editor's Choice Award.