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256GB Class SSD Performance
Comparison Products
We grabbed a group of similar 256GB-class drives to compare to the new Plextor S3C. We went through a dry spell in this capacity but received a few new products over the last couple of months. The 3D revolution brings larger die sizes in tow, so this capacity is the new entry-level for many product families. By 2018, we will rarely receive 256GB drives for testing as the industry moves to 512GB models for the mainstream.
The Corsair Force LE 200 240GB and HP S700 250GB are both DRAMless models. The Force LE 200 uses a Phison S11 controller, and the S700 uses the SMI SM2258XT. The Mushkin Triactor 240GB, Samsung 850 EVO 250GB, and SanDisk Ultra II 240GB use a DRAM buffer. These are established products that have shipped for several months to several years.
Sequential Read Performance
To read about our storage tests in-depth, please check out How We Test HDDs And SSDs. We cover four-corner testing on page six of our How We Test guide.
You won't find a significant difference between most modern SSDs when they read sequential data. Our tests show that most of these products deliver 500 MB/s or more at very low queue depths.
Sequential Write Performance
You will see much more variation during the sequential write tests. Companies use different algorithms to write this type of data to TLC flash. The preferred method is to use flash that is fast enough to keep the data rate high, like the 3D NAND in Samsung's 850 EVO. Some SSDs, like SanDisk's Ultra II, use slower flash and a folding technique that stores incoming data on an intermediary SLC buffer. Our favorite is direct-to-die writes. This technique circumvents the SLC buffer when it is full to ensure consistent performance.
Sequential Write Cache Effect
The Plextor S3C 256GB appears to use a form of direct-to-die writes after the SLC buffer fills. The problem is the flash's write speed is very slow compared to many of the other products. The Sk Hynix 14nm TLC in this configuration can write at 170 MB/s using 128KB sequential blocks. The speed is high enough that you will not feel like the drive slows down your network transfers, but it's less than ideal for installing software from a local drive.
Random Read Performance
Random read performance at very low queue depths has a direct relation to the overall user experience. At first glance, the performance seems reasonable given the Plextor S3C 256GB's $100 price point. The problem is Samsung's 850 EVO 250GB also retails for roughly $100.
Random Write Performance
The S3C matches the HP S700 250GB DRAMless SSD in random writes at queue depth (QD) 1 and 2. The HP continues to scale well for a DRAMless drive, but the S3C hits a wall around 40,000 IOPS and refuses to scale further as we increase the workload.
80% Mixed Sequential Workload
We describe our mixed workload testing in detail here and describe our steady state tests here.
Entry-level and mainstream SSDs often suffer from low mixed workload performance. The charts are full of these products, except the 850 EVO. It has ascended into the upper class even though it sells in the same price range as the other products.
80% Mixed Random Workload
The 80% read mixed random test gives us a better look at the product hierarchy. The two DRAMless SSDs quickly fall to the bottom of the performance charts, while the mainstream drives cluster together in the middle.
Sequential Steady-State
Given the new direction the consumer SSD has taken, we can no longer say that TLC products are not designed for heavy sustained workloads. We are about to turn that corner in the near future, but the Plextor S3C isn't in that room. We did see a slight uptick in the 100% write portion of the test, but the S3C only matches the SanDisk Ultra II 240GB.
Random Steady-State
The random write steady-state test shows us performance as the cache fills and flushes. The result is inconsistent performance, but unlike the HP S700, it does allow the S3C to stay off the performance floor.
PCMark 8 Real-World Software Performance
For details on our real-world software performance testing, please click here.
Application performance only varies by a second or less for most tests. As you ramp up the workload, like in the heavy Photoshop test, the drives separate a bit more. For many, the time difference is small enough to consider the drives equal. The seconds add up if you run these applications several times a day, though. Loading a game level every half hour and saving a couple of seconds doesn't seem like much. Loading an image in Photoshop every few minutes and saving six seconds in each instance may be a bit different.
Application Storage Bandwidth
The Plextor S3C lands between the Mushkin Triactor and HP S700. The drive is still quite a bit off of the performance benchmark set by the Samsung 850 EVO 250GB, and that will keep many of our readers from considering this product.
PCMark 8 Advanced Workload Performance
To learn how we test advanced workload performance, please click here.
Coming off of a heavy workload, the Plextor S3C 256GB keeps pace with the Samsung 850 EVO. This is a test that historically hasn't favored Plextor SSDs. Several Plextor SSDs have had issues with this test, but those products all used Marvell controllers with Lite-On developed firmware.
Total Service Time
The Plextor/SMI combination seems to have fixed the recovery latency issues, at least for this product. With the S3C near full capacity, the performance is very similar to the 850 EVO SSD.
Disk Busy Time
The S3C separates itself from the DRAMless SSDs during the disk busy time test. The line chart measures the amount of time it takes to complete several tasks. This is sometimes called "time to completion," and it's an important test for storage because the SSD can return to a low power state quickly after it completes the task.
Responsiveness Test
The Responsiveness Test comes from BAPCo's SYSmark 2014 SE software suite. It uses real software and realistic workloads to measure response time and latency. This is one of the best tests we've run for comparing the user experience. The test also measures system-level power consumption. We use a Lenovo Y700-17 with an Intel 6700HQ processor for the two BAPCo software suites.
Notebook Battery Life
The Plextor S3C 256GB achieved 331 minutes in our Lenovo Y700-17 gaming notebook running MobileMark 2012.5. The test runs through a typical office workload using real-world software like Microsoft's Office and Adobe's suites, along with Winzip and other popular productivity applications.
Notebooks restrict the CPU, DRAM, and DMI buses to save power when they are running on battery. Thisaffects the system performance as a whole, but it also hurts storage performance. Some drives perform well under the restricted power conditions, but others lose more performance than expected. The Plextor S3D 256GB falls into the latter category. System performance drops off sharply when the system is on battery power.
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