A Sexy Form Factor You'll Want More Than Need
The M6e is fast. There's no doubt about that. It's able to hang with the other high-end SSDs we've ever tested. In fact, SanDisk's M.2-based, PCIe-attached A110 is similar, though also a bit faster. But you can't buy the OEM-only A110, whereas Plextor's offering is for sale on Newegg right now.
There's just one catch: two models are up on the site, and both include a four-lane adapter card for the two-lane M6e. The M.2-only version is still on its way. If you pop the little card off of its adapter, your warranty is voided. So, you don't want to buy the M6e for a notebook or desktop motherboard with an M.2 interface just yet. Rather, the 128 and 256 GB drives available today should live life inside a desktop machine with a spare PCI Express x4 link. That lets us narrow down our focus for making recommendations.
Our synthetic benchmarks show sequential read and write performance hundreds of megabytes per second faster than the quickest SATA-based SSDs. Random performance is also excellent, though it's not interface-limited, so PCIe doesn't really convey a quantifiable benefit. I can't say you're going to notice those blazing-fast sequential numbers in day-to-day use, and with random performance no better than the fastest SATA 6Gb/s drives, performance is ultimately a wash for the M6e.
We do see praiseworthy behavior in our write saturation testing, though. With one-second granularity, Plextor's M6e looks a lot like Intel's consistent SSD DC-series drives, including the enthusiast-oriented SSD 730. Those offering surpass Plextor's I/O throughput thanks to significant over-provisioning, but the M6e is at least able to serve up information in well-controlled bands.
This consistency is something Plextor is cooking up for enterprise-class storage, and we're glad to see it applied in the consumer space as well. Most enthusiasts won't see or feel the difference in consumer workloads, but that isn't the point. Devices like Intel's SSD 730 and Plextor's M6e are two of the only drives we've seen behave this way, displaying grace under the pressure of more taxing applications.
TRIM testing turns up another bright spot. Plextor's 9183-based drive behaves exceptionally for an SSD with just 7% over-provisioning, outshining the M5 Pro. It cannot lay a finger on SanDisk's X210 though, a device that shows itself to be outstanding in a number of metrics. You don't get the same screaming sequential numbers (it's hamstrung by the SATA interface, after all). In its degraded state, however, the X210 maintains the lowest write access latency imaginable.
All of that is to say the M6e's PCI Express controller and M.2 form factor, on their own, don't confer an advantage in the most meaningful benchmarks.
There are still questions left to answer about PCI Express storage and its interaction with the AHCI standard. In our Tom's Hardware Storage Bench, we recorded notably different service time profiles under Windows 7 and 8.1. In Windows 7, using Microsoft's built-in MSAHCI.SYS, the numbers look great. Windows 8.1, on the other hand, employs a newer AHCI driver that's far less kind to the M6e, other PCIe-based devices, and even familiar SATA SSDs. Intel may address this in the future with its own software for integrating AHCI- and NVMe-based PCIe storage into its platform architecture.
Finally, our newest PCMark 8-based storage test doesn't give the M6e much of an advantage either. Samsung's 840 EVO and Plextor's M5 Pro soar in the Storage Consistency test. Drives from Intel, SanDisk, and Adata dominate as well. Meanwhile, the M6e's performance is more ordinary than I was expecting given its interface and pedigree.
All of that would be fine if Plextor was hitting the right price points. But you can pick up three Crucial M550s for what the same $300 being asked for a 256 GB M6e. Sling them together in RAID 0 and you have enough throughput to saturate Intel's DMI interface (I'd be willing to guess that's almost 1500 MB/s in sequential reads and 1000 MB/s in writes).
Plextor's price tags could make more sense if we were looking at M.2 models (without the adapter) for notebooks, where multiple SATA drives aren't as easy to pull off. In a desktop, it's slightly more difficult to make a case for $1+/GB solid-state storage, even if it's attached through the PCI Express bus.
Of course, there's another way of looking at this. The M6e's simplicity and elegance (that is, a native PCIe controller) put it far ahead of the PCI Express-based SSDs we've reviewed in the past. Most of those needed multiple SATA controllers attached to host bus logic. And they were way more expensive than $300 for 256 GB.
There are pros and there are cons. No matter what, though, enthusiasts are going to find Plextor's M6e desirable. It's a great solution for loading Windows and launching performance-sensitive applications, leaving native SATA ports open for a big RAID array. As a storage fiend, it's easy to see how the M6e matched up to big mechanical disks would be a fun combination. And even if the M6e only really moves the needle in sequential transfers, the M.2-based version, without a bundled adapter, promises to satisfy mobile enthusiasts.
If Plextor can bring its price down over time, its unique brand of performance and this cutting-edge form factor should attract lots of attention. Again, though, we're most excited about the M.2-specific version. On the desktop, for what Plextor is charging today, there are more compelling solutions available.