Being an industry leader requires a willingness to blaze trails in previously unexplored areas. Samsung is the world's largest NAND memory fabricator, and they have displayed a repeated willingness to lead with innovative products. The latest transition began in the client space with the 840 EVO. Samsung initially released this three-bit-per-cell (TLC) SSD last year, even though some felt trepidation at its lowered endurance.
Samsung allayed the hyperventilating enthusiasts' fears by providing a solid warranty, innovative techniques to boost performance, and a line of compelling features. A year later, the use of TLC NAND is commonplace. The 840 Evo is known for performance, reliability, and its competitive price point.
Samsung already has the PM853T 3bit MLC NAND SSD in the OEM space, and the company has expanded that out into the retail market with the 845DC EVO. Samsung has the strategic advantage of being the only SSD manufacturer with a 3bit NAND SSD on the market. While others are bringing inaugural products to market soon, Samsung is already moving ahead with expanded applications for value-oriented 3bit NAND.
Samsung is delivering the same value proposition presented to the client space into the datacenter, but with enhanced features and a longer five-year warranty. The latest enterprise SSD releases have all focused on delivering the best value for users, and Samsung plans on driving even more value into the datacenter with its 845DC EVO. This starts by utilizing 19nm Toggle 3bit MLC NAND and pairing it with a 2 million hours MTBF and an UBER rating of 1 sector per 10^17 bits read. These industry-standard reliability metrics should assuage any concerns about reliability.
The 845DC EVO features adequate endurance numbers for read-centric entry-level workloads, such as read-cache, search/indexing, and content delivery, workstation, and webserver applications. Cheap client SSDs fulfilled these entry-level datacenter workloads in the past, but the expansions of manufacturers' product stacks have provided more datacenter-friendly options.
In comparison to the other products in our test pool, the 845DC EVO has a lower endurance level of only 0.35% Drive Writes Per Day (DWPD). The 845DC EVO is purpose-built for read-centric applications, and even some of the latest cutting-edge PCIe SSDs feature only 0.3% DWPD to address similar workloads.
The 845DC EVO comes in the 2.5-inch form factor in capacities of 240GB, 480GB, and 960GB. Performance specifications are very competitive, starting with a class-leading 87,000 random read IOPS. Random write IOPS weigh in at 14,000 IOPS for the 480GB and 960GB capacity points, and the 240GB drive offers 12,000 random write IOPS. Sequential read speed is 530 MB/s for all capacity points, and the write speed is 410 MB/s for the 480GB and 960GB models, and 270 MB/s for the 240GB.
One of the primary differentiators between client and enterprise SSDs is power loss protection. Samsung brings this feature, which was noticeably absent in the SM843 but included in the SM843T, into the design of the 845DC EVO. The 845DC EVO also touts advanced signal processing for error correction and end-to-end data protection built into the datacenter-optimized firmware.
Samsung has also begun a concerted effort to offer more consistent performance. Samsung is issuing a QoS spec that guarantees completion of 99.9 percent of read operations in 0.6ms, and write operations are spec'd at 99.9 percent under 7ms. There are also guarantees that maximum read will not top 115us, and write operations will stay under 55us. These limitations on maximum I/O are important for RAID and replicated environments, and it is encouraging to see more manufacturers stepping up and offering performance guarantees.
The three-bit-per-cell generation for the datacenter begins with the 845DC EVO, so let's take a closer look at the components.
Samsung 845DC EVO Internals and Specifications
Samsung 845DC EVO Internals
The Samsung 845DC EVO comes in a 2.5-inch form factor with a 7mm z-height in the typical Samsung motif.
The case is bereft of thermal pads, indicating that the 3bit NAND may run cooler than typical 2bit. Twenty-one tantalum capacitors are dispersed on the PCB, with several pads open for more capacitors in the high-capacity model.
Four 128GB packages of Samsung 19nm Toggle 3bit MLC NAND populate the rear of the PCB. Each package features eight dies with 16GB per die. The top of the PCB, which houses the controller and DRAM, also has extra pads for the four additional packages required for the 960GB model.
The Samsung S4LN045X01-8030 controller, more commonly known as the MEX, is a 400MHz eight-channel Cortex R4-based ARM controller. This is a tri-core controller designed and manufactured by Samsung. Pairing this with 1GB of LPDDR2 DRAM completes the Samsung-only build.
Samsung 845DC EVO Specifications
Test System and Methodology
Our approach to storage testing targets 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 they fall short in providing the clearest view possible of I/O Quality of Service (QoS).
'Average' results do little to indicate 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 utilize high-granularity I/O latency charts to illuminate performance during our test runs.
Our testing regimen follows SNIA principles to ensure consistent, repeatable testing, and our multithreaded workloads accurately represent production environments. We measure power consumption during precondition runs. This provides measurements in time-based fashion, with results every second, to illuminate the behavior of power consumption in steady state conditions. We also present IOPS-to-Watts measurements to highlight efficiency.
All three SSDs are 480GB and are tested over their full LBA range to highlight performance at maximum utilization. The first page of results will provide the 'key' to understanding and interpreting our test methodology.
Benchmarks - 4k Random Read/Write
4k Random Read/Write
We precondition the 480GB Samsung 845DC EVO for 9,000 seconds, or two and a half hours, receiving performance reports every second. We plot this data to illustrate the drive's descent into steady state.
This dual-axis chart consists of 18,000 data points, with the IOPS on the left and the latency on the right. The green dots signify IOPS, and the grey dots are latency measurements during the test. We place latency data in a logarithmic scale to bring it into comparison range. The lines through the data scatter are the average during the test. This type of testing presents standard deviation and maximum/minimum I/O in a visual manner.
Note that the IOPS and latency figures are nearly mirror images of each other. This illustrates high-granularity testing can give our readers a good feel for latency distribution by viewing IOPS at one-second intervals. This should be in mind when viewing our test results below. This downward slope of performance only occurs during the first few hours of use, and we present precondition results only to confirm steady state convergence.
Each level tested includes 300 data points (five minutes of one second reports) to illustrate performance variability. The line for each Outstanding I/O (OIO) depth 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 Samsung 845DC EVO blows past the competition with a beastly 85,155 IOPS at 256 OIO. The Micron M500DC averages 56,259 IOPS, and the Intel DC S3500 averages 57,769 IOPS. The 845DC EVO delivers dominating performance in 100% random read environments.
The 845DC EVO leads convincingly with the lowest latency during 4k random read activity.
Garbage collection routines are more pronounced in heavy write workloads, leading to performance variability.
The 845DC EVO manages to best the DC S3500 and its 13,841 IOPS, but the Micron M500DC is terrific with 39,089 IOPS at 256 OIO. The 845DC EVO and the Micron M500DC trade blows, with unrivaled read performance from the EVO and unchallenged write performance from the M500DC.
The Samsung and Micron feature consistent latency characteristics, but the Micron has much lower overall latency in the write workload. The DC S3500 experiences some turbulence under heavy load at 256 OIO.
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. Mixed workload testing reveals strengths and weaknesses that remain hidden during typical tests. In reality, much of the real-world data is going to feature mixed data.
The Micron and Samsung dominate opposite ends of the spectrum, but our mixed testing tends to separate the wheat from the chaff. The M500DC leads eight of the 11 tests with mixed workloads, but the 845DC EVO enjoys a lead over the Intel drive, especially with heavy read workloads.
We record power consumption measurements during our precondition run. We calculate the stated average results after the device has settled into steady state during the last five minutes of the test.
The 845DC EVO features low power consumption with a 4k write workload, weighing in at 3.55 watts. The M500DC averages 4.09 watts, and the DC S3500 averages 3.8 watts during the measurement window.
IOPS-to-Watts measurements are generated from data recorded during our precondition run, and the stated average is from the last five minutes of the test. We measure efficiency based upon the write workload, but we are addressing this shortcoming with new power testing equipment from ULINK Technology. In the coming weeks, we will provide read efficiency performance measurements as well.
The 845DC EVO averages 3,973 IOPS-per-Watt. The M500DC jumps to a big lead, averaging 9,545 IOPS-per-Watt, due to its outstanding write performance. The DC S3500 averages 3,125 IOPS-per-Watt.
Benchmarks - 8k Random Read/Write
8k Random Read/Write
Server workloads rely heavily upon 8k performance, and we include this as a standard with each evaluation. Many of our server workloads also test 8k performance with various mixed read/write workloads.
The average 8k random read speed of the 845DC EVO is 52,731 IOPS. The Micron M500DC is 48,034 IOPS at 256 OIO, and the Intel DC S3500 measures 44,444 IOPS. The 845DC EVO provides impressive read speed, but does not beat the M500DC by nearly as large of a margin as observed with 4k random read activity.
All three SSDs exhibit a tight latency range during the 8k random read test.
The M500DC easily leads with an average of 23,852 IOPS. The 845DC EVO comes in second with 7,112 IOPS, and the DC S3500 averages 6,937 IOPS.
The M500DC owns the 8k mixed workload testing with a large lead during the test. While the 845DC EVO and the DC S3500 have a tighter performance profile, they are well below the M500DC.
Power consumption for the 845DC EVO averages 3.54 watts; the M500DC averages 4.77 watts, and the DC S3500 averages 3.75W.
The M500DC leads the efficiency test convincingly with 4,877 IOPS-per-Watt; the 845DC EVO averages 1,994 IOPS-per-Watt, and the DC S3500 averages 1,584 IOPS-per-Watt.
Benchmarks - 128k Sequential Read/Write
128k Sequential Read/Write
128k sequential speed reflects the maximum sequential throughput of the SSD. The 845DC EVO leads the sequential read tests with an average of 526 MB/s at 256 OIO. The Micron M500DC features the lowest sequential performance specifications of the value-SSD lineup and averages 417 MB/s, while the Intel DC S3500 delivers an average of 441 MB/s.
The 845DC EVO provides the lowest overall latency.
The 845DC EVO averages 427 MB/s. The M500DC averages 388 MB/s, and the DC S3500 is within striking distance of the EVO with 424 MB/s.
On the surface, the 845DC EVO would appear to be the best SSD with sequential read and write activity. Our mixed workload testing reveals otherwise. The 845DC EVO and DC S3500 both exhibit a 'bathtub' performance profile with sequential workloads. The high marks in pure read/write environments are accompanied by sagging performance in the middle. The slightest of mixed workloads sends their performance much lower, while the M500DC delivers steadier performance throughout the test. The 845DC EVO and DC S3500 actually only lead in two of the 11 tests.
The 845 DC EVO wins with an average of 4.14 watts. The M500DC averages 5.24 watts, and the DC S3500 averages 4.83 watts.
The 845DC EVO is the most efficient sequential drive in write environments with an average of 99 MB/s-per-Watt. The M500DC averages 73 MB/s-per-Watt, and the DC S3500 averages 87 MB/s-per-Watt.
Benchmarks - Database/OLTP and Web Server
This Database and On-Line Transaction Processing (OLTP) workload is a demanding 8k random test with a 66 percent read and 33 percent write distribution. OLTP is the processing of transactions such as credit cards and high frequency trading in the financial sector. Databases are the bread and butter of many enterprise deployments, and these workloads bring even the best solutions down to earth.
The Samsung 845DC EVO has a very consistent average of 19,678 IOPS at 256 OIO. The Micron M500DC tops the chart with an average of 21,133 IOPS but experiences significant variability, and the Intel DC S3500 averages 19,400 IOPS at 256 OIO. The significant variability from the M500DC muddies the performance picture, while the 845DC EVO comes in slightly lower with very consistent performance.
The 845DC EVO averages 3.55 watts. The M500DC averages 2.76 watts, and the DC S3500 averages 3.76 watts.
The 845DC EVO averages 5,465 IOPS-per-Watt. The M500DC averages 7,676 IOPS-per-Watt, and the DC S3500 averages 4,040 IOPS-per-Watt.
The Web Server workload is a read-only test with a wide range of file sizes. Web servers are responsible for generating content users 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 hosting the website.
The 845DC EVO leverages its excellent performance in pure read environments and delivers an impressive 28,054 IOPS at 256 OIO. The M500DC averages 18,650 IOPS, falling to the DC S3500's average of 23,664 IOPS.
The 845DC EVO averages 3.55 watts. The M500DC averages 3.21 watts, and the DC S3500 requires 3.8 watts during the Web Server workload.
The 845DC EVO scores 914 IOPS-per-Watt. The M500DC scores 1,965 IOPS-per-Watt, compared to 749 IOPS-per-Watt for the DC S3500.
Benchmarks - Email Server
The Email Server workload is a demanding 8k test with a 50 percent read and 50 percent write distribution. This application is indicative of the performance in heavy write workloads.
The 845DC EVO averages 14,041 IOPS. The Micron M500DC averages 15,403 IOPS, and the Intel DC S3500 averages 13,121 IOPS at 256 OIO.
The 845DC EVO averages 3.54 watts. The M500DC averages 2.66 watts, and the DC S3500 averages 1.75 watts.
The 845DC EVO averages 3,815 IOPS-per-Watt. The M500DC averages 5,806 IOPS-per-Watt, and the DC S3500 scores 6,705 IOPS-per-Watt.
One of the recurring themes from NAND fabs is the vertical-integration message, and for good reason. Samsung is a good example of a company that reaps the benefits from in-house production of every component. While Samsung is solidifying their position in 3bit NAND, they are also moving aggressively with their V-NAND (3D NAND) products that they began sampling a year ago. Their in-depth knowledge of their own NAND, DRAM, and controllers provides a benefit beyond component cost and profit margins. The ability to develop new components and rapidly adjust firmware is a benefit that grants them a time-to-market advantage.
Samsung addresses concerns about 3bit NAND longevity with a longer warranty period and clear communication of endurance metrics. Users should know their workload, and for those with read-centric applications, the 845DC EVO presents a compelling value offering. Deploying SSDs into various RAID configurations in production environments also distributes the write workload over several drives.
Samsung also provides RAID performance specifications in their documentation, and we included those measurements on the spec page in this article. These specifications highlight the scaling ability of the 845DC EVO in RAID environments. Much of the enhanced scaling is due to the enhanced QoS focus from Samsung. We are conducting tests to investigate the performance of several leading value-class SSDs in RAID configurations, so stay tuned for more information and direct comparisons.
In reality, a 3bit NAND SSD delivers more useable write endurance than an HDD can provide. While the platter of an HDD has a very high tolerance for heavy workloads, the mechanics of the moving parts conspire to hinder the speed, and thus the useable endurance of the drive. The 960GB 845 DC EVO provides 336GB of write endurance per day for five years. In our testing, the fastest 15k HDDs write at a speed of roughly 450 IOPS for 4k random write workloads. This equates to roughly 148GBs of data written per day.
The 845DC EVO provides 600TB of write endurance in five years, compared to the fastest of hard drives providing only 263TB. For users upgrading from HDDs to an 845DC EVO, the value proposition is clear: the Samsung provides faster performance at a competitive price per GB, along with the added benefit of more useable write endurance over the life of the drive.
Performance of the 845DC EVO was spectacular in heavy read workloads, and the other drives fell far behind. The EVO is designed for read-centric workloads and fell into an expected performance profile with write activity. The 845DC EVO managed to outpace the Intel DC S3500 in most tests, but the M500DC tended to deliver more robust write performance in random environments. The 845DC EVO dominated pure read/write sequential activity, but the M500DC is hard to beat in mixed sequential workloads. The EVO also delivered consistent performance in the OLTP workload, and fared well in our power testing.
At the time of publishing, the 845DC EVO is priced very aggressively at roughly $1/GB. With volume pricing, there will be excellent price points, especially when 3bit NAND products from other manufacturers hit the market and foster competition. For now, its price leads the market.
The evolution of flash has always been about driving more performance into the datacenter with a lower TCO. The 845DC EVO delivers on that vision by offering a customized data storage solution for read-centric applications. Value-focused offerings for these applications are important; it is never wise to spend money on an underutilized resource, such as endurance. The Samsung 845DC EVO offers datacenter-class features at a lower price point and a five-year warranty, earning the TweakTown Best Value Award.
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