Benchmarks And Comparisons
The price of the Intel SSD 540s falls in line with mainstream products, but the performance specifications match entry-level SSDs. That stated, we chose to use the entry-level performance test pool for this performance comparison. The mainstream SSD market has shrunk over the last year. TLC flash prices are in a free-fall, but MLC prices are increasing simultaneously as production shifts to high-capacity, instead of high performance, NAND.
The Adata SP550 uses the previous generation SMI SM2256 controller paired with SK Hynix TLC flash. The drive closely resembles the Intel SSD 540s we're testing. It joins the Crucial BX200, MyDigitalSSD BP5e and OCZ Trion 150 (now officially called TR150) in the entry-level comparison group.
The Mushkin Reactor and Samsung 850 EVO are the two mainstream SSDs on the list that we compare to the Intel SSD 540s.
Sequential Read Performance
Reading data sequentially from the flash is one of the easiest tasks for an SSD. All of the devices perform well at high queue depths, but we find variation at the lighter queue depths, which is where desktop and notebook operating systems perform most of the read operations. We isolated queue depth 2 performance and found that nearly all of the products achieve over 500 MB/s at this key threshold. The Intel SSD 540s landed near the bottom of the chart with 516 MB/s.
Sequential Write Performance
We see much more performance variation during the sequential write test. Many of the drives on the chart utilize a two-tier approach for storing incoming write data. The SSD has a small SLC buffer area of the flash that operates in one-bit-per-cell mode. The SSD writes data to this area first, which increases write performance. Unfortunately, the SLC buffer consumes three times more capacity compared to TLC flash, so SSD vendors limit the size of the buffer. The SSD migrates the data from SLC to the slower three-bit per cell (TLC) NAND when it depletes the SLC portion of the flash. Users do not notice the transition if the SLC buffer is large enough.
Each company uses a different algorithm. Phison innovated a new direct-to-die write system for writing data directly to the TLC area. This MyDigitalSSD BP5e and OCZ Trion 150 use this technique.
Here we see a test that writes 128 KB sequential data to the full user space of the Intel SSD 540s. The native TLC transfer performance, which occurs outside of the SLC buffer, measures around 135 MB/s. The performance is high enough to accept a file transfer at full speed over a gigabit Ethernet connection.
Random Read Performance
There is very little separation during random reads at low queue depths, with the exception of the Samsung 850 EVO 500 GB. The Intel SSD 540s is the fastest non-Samsung SSD using three-bit per cell flash, and it sits just behind the performance of the MLC-powered Mushkin Reactor 512 GB at a queue depth of one. The 540s scales well as the queue depth increases, but it fails to reach the 850 EVO's performance.
Random Write Performance
The Intel SSD 540s with the SMI SM2258 delivers higher random write IOPS than the Adata SP550, which uses the previous generation SM2256 controller and similar SK Hynix flash memory. We suspect the newer SM2258 controller is nearly identical to the SM2256 aside from a clock speed increase, which allows the controller to process data faster. Neither product performs exceptionally well with random data writes, and both trail the class-leading 850 EVO by 10,000 IOPS at queue depth 1.
80 Percent Sequential Mixed Workload
Intel's 540s marketing documents discuss mixed workload optimizations. We're glad to see the consumer SSD industry stop tuning drives for high benchmark scores with unrealistic workloads and instead focus more on tuning SSDs for real-world workloads.
The Intel SSD 540s performs really well in the sequential mixed workload test. The SLC buffer in most of the products creates waves in the test results, so we have to examine the results and normalize the data. The queue depth 2 and 4 results hold more value than the higher queue depths.
80 Percent Random Mixed Workload
The Intel 540s would provide chart-topping performance compared to the other TLC-based products if you remove the Samsung 850 EVO 500 GB from the mixed sequential results. The MLC-powered Mushkin Reactor is only slightly faster at a few queue depths, but the 540s operates at roughly the same speed. I'm sure there are many SSD manufacturers that would like to remove the 850 EVO from the picture, but with its low price point and high performance, it's here to stay.
The Intel SSD 540s provides strong performance in steady-state conditions when the majority of the workload is read-centric. Write-intensive tasks prove to be problematic for this SSD, but as a low-cost entry-level model, Intel didn’t design the 540s for heavy write environments.
I've always wondered how Intel would handle performance consistency with an entry-level SSD. The 7-Series products (both the PCIe and SATA models) place a lot of emphasis on keeping the data flow consistent. The 540s documentation doesn't say much about performance consistency at all, but we can't blame Intel for sweeping the topic under the rug with this product.
The Intel SSD 540s is not the SSD you want to use in RAID 0 on motherboards. The SSD 730 is an excellent choice, though.