Plextor M6 Pro 256GB SSD Review

1. Introduction & Specifications, Pricing, and Availability
2. Plextor M6 Pro 256GB SSD
3. Test System Setup and Initial Performance
4. Benchmarks - Sequential Performance
5. Benchmarks - Anvil Storage Utilities
6. Benchmarks - Mixed Read / Write Workloads
7. PCMark 8 Consistency Test
8. PCMark 8 Consistency Test - Continued
9. Final Thoughts

Introduction & Specifications, Pricing, and Availability

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This review wraps up a long run of Plextor product reviews that started with the M6M, moved through the M6e Black Edition series, and concludes with the M6 Pro products like the 256GB model we have here today.

As we discussed in the M6 Pro 128GB review, the M6 Pro product series got off to a rocky start. Our samples were delivered in person at Flash Memory Summit back in August 2014, and we planned to get enough performance data at the show to write a quick preview article, but we stumbled across a few performance and stability issues. Within a few weeks, the M6 Pro drives went on sale, and not long afterward, owners complained about data loss, instability, and failed products. Plextor pulled these products from Newegg, Amazon, and other e-tail outlets, and a few forum posts even spoke of a recall. However, Plextor never announced a recall in a press release.

It didn't take long for Plextor to release firmware 1.02 to fix the stability issues and get the drives back on the market. When released, the M6 Pro series was priced a bit higher than most of us were willing to spend. This is a premium product with a very nice accessory package, but premium products need to have high performance to justify the higher cost.

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After another couple of months of tinkering with the firmware, Plextor released version 1.03. This firmware release addresses issues with performance consistency under heavy load. If you are buying a premium SSD, you are doing it for a reason. The M6 Pro isn't just a HDD replacement product, it's a performance SSD for heavy multitasking, gaming, and content creation.

Specifications, Pricing, and Availability

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Plextor released the M6 Pro in four capacities that range from 128GB to 1TB. Today we're focusing on the 256GB model. The M6 Pro 256GB features a sequential read speed of over 545 MB/s, and a sequential write speed of 490 MB/s. The sequential performance is the same on the three larger capacity M6 Pro products. The random read performs tops 100K IOPS, and the random write performance comes in at 88K IOPS. The random write performance is only 2,000 IOPS less than the 512GB and 1TB models at queue depth 32.

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Plextor's TrueSpeed and TrueProtect features have been around for a few launches now, and so has DEVSLP, which isn't exclusive to Plextor SSDs. PlexTurbo was introduced with the M6 Pro series, and was then improved upon with PlexTurbo 2.0, which was introduced with Plextor's M6e Black Edition.

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The PlexTurbo feature is similar to Samsung's Magician in that it allocates DRAM to act as a cache for the storage IO. In theory, this feature increases performance and reduces the wear on the SSD's flash. Random writes are absorbed by the RAM, and sent to the drive as sequential data. Any data called that is in the RAM is read back from the RAM, which is another method of improving performance.

With the critical issues taken care of via firmware updates, the M6 Pro is now back on the market globally. The 256GB model we're testing today sells on Newegg for $155.99. The 128GB lists for $90.99, the 512GB for goes $306.99, and the massive 1TB model sells for $679.99. The 1TB model is currently out of stock at Newegg.

Plextor backs the M6 Pro with a five-year warranty. The drive ships with a SATA cable, desktop adapter bracket, and a software disk that includes PlexTurbo and migration software.

PRICING: You can find the Plextor M6 Pro 256GB SSD for sale below. The prices listed are valid at the time of writing, but can change at any time. Click the link to see the very latest pricing for the best deal.

United States: The Plextor M6 Pro 256GB SSD retails for $148.99 at Amazon.

Canada: The Plextor M6 Pro 256GB SSD retails for CDN$254.47 at Amazon Canada.

Plextor M6 Pro 256GB SSD

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Plextor pulled out all of the stops with the M6 Pro products. As you can see here, even the retail box is flashy.

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The retail package shows us a lot of information about the product, including specifications, features, warranty, a support number, and a list of everything included in the package.

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The presentation is very nice. The inner box opens, and you see the SSD in a foam holder with the texture of crushed velvet.

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Most SSDs no longer ship with a desktop adapter bracket or a SATA cable. Plextor includes the adapter bracket and cable, along with the software disk and three papers that provide warranty terms, support numbers, and installation instructions.

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The SATA cable Plextor ships along with the M6 Pro is very nice. It's much thinner than a normal SATA cable, like the ones you get with new motherboards. The software disk includes NTI Echo 3, NTI Backup Now EZ 3, and NTI Quick State Guides.

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Plextor is a Japanese brand, and they love champagne brushed aluminum. This finish started appearing on high-end home audio gear in the '80s. Even today, limited edition A/V gear still ships in this finish; it looks very good.

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The model and serial numbers are listed on the back of the drive with the notations of the drive capacity and firmware version shipped with the drive.

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The M6 Pro series products all use a 7mm z-height case design, so this SSD will fit in a newer notebook or Ultrabook that requires the slim design.

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Inside, we found a Marvell 88SS9187 multi-core controller paired with Nanya DRAM and Toshiba A19 MLC flash.

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The 88SS9187 controller has been around for a few generations now. Companies like Plextor need to develop the firmware used on the drives in-house.

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The M6 Pro ships with two DDR3 packages, each with 256GB of capacity. That means this model has 512GB of buffer area for table data.

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The MLC flash is Toshiba's second generation 19nm. Toshiba calls the flash "A19."

Test System Setup and Initial Performance

Desktop Test System

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Lenovo T440 - Notebook Power Testing with DEVSLP and Windows 8.1 Pro

Nearly all of the performance tests run on the desktop system, but we use a Lenovo T440 to run the power tests. The T440 is the latest addition to our client SSD test lab, and allows us to test the notebook battery life offered by a SSD with advanced features like DEVSLP enabled.

Initial Performance Evaluation - 4-Corner and then Some Tests

Sequential Read

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Sequential Write

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Sequential 80% Read 20% Write

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Random Read

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Random Write

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Random 80% Read 20% Write

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Nothing from our initial performance tests caused us concern. The sequential write performance peaked at 500 MB/s, which is a bit higher than Plextor's specifications that were most likely recorded with a queue depth of 32.

Benchmarks - Sequential Performance

HD Tune Pro - Sequential Performance

Version and / or Patch Used: 5.50

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To measure and compare sequential performance, we use 64KB blocks. The Plextor M6 Pro averages 452 MB/s in this test. That's a bit under many of the drives on the chart, but it's also a bit over some of the others.

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The sequential write performance averages 375 MB/s, and the minimum and maximum numbers came in a tight group. As you can see on the chart, this isn't a guarantee with newer flash and advanced SSDs that use a SLC layer to hide write performance that drops off when the buffer is full.

HD Tach - Sequential Write Performance after Random Writes

Version and / or Patch Used: 3.0.4.0

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After a number of sequential and random writes, we tested the Plextor M6 Pro 256GB with 128K sequential data to look for performance drop off in the write test. The target drive only had one severe dip that sent the write performance to around 30 MB/s.

Benchmarks - Anvil Storage Utilities

Anvil Storage Utilities

Version and / or Patch Used: RC6

So, what is Anvil Storage Utilities? Anvil Storage Utilities is a storage benchmark for SSDs and HDDs where you can check and monitor your performance. The Standard Storage Benchmark performs a series of tests; you can run a full test, or just the read or the write test, or you can run a single test, i.e. 4k QD16.

Anvil Storage Utilities is not officially available yet, but we've been playing with the beta for several months now. The author, Anvil, has been updating the software steadily on several international forums, and is adding new features every couple of months.

We can use Anvil several different ways to show different aspects for each drive. We've chosen to use this software to show the performance of a drive with two different data sets. The first is with compressible data, and the second data set is incompressible data. Several users have requested this data in our SSD reviews.

0-Fill Compressible Data

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Incompressible Data

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Using Anvil Storage Utilities, we determined the Plextor M6 Pro reads and writes compressible and incompressible data at the same speed.

Low Queue Depth Read IOPS

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Just like the M6 Pro 128GB we reviewed a few days ago, the 256GB model gets very close to 10K random read IOPS at QD1. The random read performance scales well all the way through QD32, the maximum on this chart.

High Queue Depth Read IOPS

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At the high-end of the random read scale, we found the M6 Pro 256GB running right up near 100K IOPS. The scale looks very good with improvements at every step as queue depth is increased.

Low Queue Depth Write IOPS

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The QD1 and QD4 random write tests show the M6 Pro is competitive with the best drive on the market. By QD4, the M6 Pro 256GB starts to trails off where some of the other products break 80K IOPS.

High Queue Depth Write IOPS

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The high queue depth random write chart shows the M6 Pro 256GB recovering nicely. We nearly broke 90K random write IOPS at QD32.

Benchmarks - Mixed Read / Write Workloads

Sequential Mixed Read / Write Workloads

In this series of tests, we measure mixed workload performance. We start with 100% read, and then add data writes to the mix in 10% increments until we get to 100% writes. We believe this will be the next major area SSD manufacturers will address, after performance consistency.

Sequential Mixed Workload Bandwidth

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After introducing this mixed workload test, we've heard that some SSD markets are tuning SSDs to perform better in mixed workload conditions. The M6 Pro 256GB has massive performance loss when just a small amount of data writes are added to the mix.

Sequential 80% Read / 20% Write Bandwidth

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The 80% read with 20% write test represents a typical consumer mix. This test preconditions the drives so we're just looking at steady state performance.

Random Mixed Workload Response Time

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The random mixed IO test is of interest because your computer is always reading and writing little bits of data. Everything is logged in modern Windows, and each update is a small write to the disk. The trend of this review really seems to come out in this test; the M6 Pro 256GB performs really well, but just can't catch the very best on the market.

PCMark 8 Consistency Test

Futuremark PCMark 8 Extended - Consistency Test

Version and / or Patch Used: 2.0.228

Heavy Usage Model:

Futuremark's PCMark 8 allows us to wear the test drive down to a reasonable consumer steady state, and then watch the drive recover on its own through garbage collection. To do that, the drive gets pushed down to steady state with random writes, and then idle time between a number of tests allows the drive to recover.

Precondition Phase:

1. Write to the drive sequentially through up to the reported capacity with random data.

2. Write the drive through a second time (to take care of overprovisioning).

Degradation Phase:

1. Run writes of random size between 8*512 and 2048*512 bytes on random offsets for ten minutes.

2. Run performance test (one pass only).

3. Repeat one and two, eight times, and on each pass, increase the duration of random writes by five minutes.

Steady state Phase:

1. Run writes of random size between 8*512 and 2048*512 bytes on random offsets for 50 minutes.

2. Run performance test (one pass only).

3. Repeat one and two, five times.

Recovery Phase:

1. Idle for five minutes.

2. Run performance test (one pass only).

3. Repeat one and two, five times.

PCMark 8's Consistency test provides a ton of data output that we use to judge a drive's performance. Here we see the three states of performance for the select SSDs, light use, consumer steady state, and worst case.

Storage Bandwidth - All Tests

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Here we get our first look at PlexTurbo with the M6 Pro 256GB SSD. The new 1.03 firmware was released to increase the M6 Pro's steady state performance under real-world workloads like those that we see here.

Storage Bandwidth - Heavy Load

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Under heavy load, the drive lacks the high performance we look for in a premium performance SSD. Even with PlexTurbo enabled, the M6 Pro fails to impress.

Storage Bandwidth - Typical Consumer Load

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In the consumer workload tests, we see very little throughput performance difference between the M6 Pro 256GB with and without PlexTurbo. We'll measure with a different metric on the next page, and see a different result, but if you're looking for more throughput, PlexTurbo doesn't bring it to the real-world.

PCMark 8 Consistency Test - Continued

Total Access Time - All Tests

The access time test measures the total latency across all 18 tests. This is one of, if not the most important of all the tests we run at this time for consumer SSDs. When your latency is low, your computer feels fast; it's just that simple.

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PlexTurbo and other cache software are designed to decrease latency. When you have low latency, your computer feels fast; and when the latency is high, your computer feels sluggish, unresponsive, and slow.

Total Access Time - Heavy Load

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PlexTurbo does decrease latency, even under heavy loads. It's too bad the base performance without the software cache running doesn't give us better results.

Total Access Time - Typical Consumer Load

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In the consumer workload latency test, the M6 Pro 256GB performs worse than any other drive on the chart. PlexTurbo does a good job of reducing latency, but there are some places where you don't want to use DRAM to cache data, like in notebooks.

Final Thoughts

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Plextor's latest SATA 6Gbps SSD is only a marginal improvement in performance over the previous generation, but the company's move to software caching gives buyers something to cheer about. PlexTurbo is more than just a trinket to improve synthetic benchmark performance; it really does save the M6 Pro.

In years past, Plextor pulled a lot of performance from the company's premium products. As flash lithography shank, so did Plextor's ability to deliver the highest levels of performance. The fab companies with intimate knowledge of the flash and the ability to program SLC like cache layers have pushed the smaller independent companies to the middle of the performance spectrum.

We've said it a number of times before, but the fabs are taking over, and that doesn't leave a lot of room for specialty companies like Plextor. LiteOn, the builder, does really well making products for the OEM market where price and stability overshadow performance. With the M6e and M6 Pro drives unable to compete at the highest end like previous generations, we wonder how much longer Plextor will continue to push the brand as a premium choice.

At $155.99, the M6 Pro 256GB costs more than SanDisk's amazing Extreme PRO 240GB, but a bit less than Samsung's 850 Pro. The Extreme PRO and the 850 Pro are the two performance leaders on the market. I don't see many people choosing the Plextor M6 over the SanDisk Extreme PRO unless the buyer needs the accessory package that includes a desktop adapter bracket and SATA cable, and runs the drive in a desktop.

Most users wouldn't want to run the M6 Pro in a notebook with the PlexTurbo software. Even without the software, we never finished a notebook battery life test without an error. This leads us to believe the drive doesn't like hard shutdowns that occur when you completely run out of battery power and don't finish a graceful shutdown. PlexTurbo uses DRAM to cache IOs, and DRAM uses battery power faster than NAND.

It will be interesting to see if Plextor continues developing the M6 Pro firmware, or if the company has dedicated all of their resources to upcoming products like the M7e PCIe NVMe drive they had on display at CES. Let's hope the company can delegate someone to improving performance without the software cache to hide weak points in the base product.

PRICING: You can find the Plextor M6 Pro 256GB SSD for sale below. The prices listed are valid at the time of writing, but can change at any time. Click the link to see the very latest pricing for the best deal.

United States: The Plextor M6 Pro 256GB SSD retails for $148.99 at Amazon.

Canada: The Plextor M6 Pro 256GB SSD retails for CDN$254.47 at Amazon Canada.