Sign in with
Sign up | Sign in
Micron P400m SSD Review: High Endurance MLC Is Here To Stay
By ,
1. Micron P400m: Is High-Endurance MLC Here To Stay?

Look back to 2010, just a few short years ago. If you wanted a storage solution that was responsive, reliable, and robust, you probably turned to SLC NAND-based SSDs. They were inordinately expensive, but spending more was justified based on their performance and reliability.

But MLC NAND, which you typically find in desktop-oriented drives, has its own advantages, too. It's cheap, in part thanks to incredibly high production volumes, and it can already be found mated to cutting-edge controller designs. In fact, in 2009, according to Forward Insights, MLC accounted for 90% of the total solid-state capacity shipped. Of course, the trade-off is that MLC must endure high latencies, and can only offer endurance a fraction of what you get from SLC NAND. Even with lots of redundancy and low cost, MLC-based SSDs were just too unreliable for the workloads typical of an enterprise environment.

The industry was at a crossroads. With cloud computing on the rise and a trend toward big data, there quickly came a need for products that combined the benefits of SLC and MLC technologies, while minimizing their drawbacks. Would manufacturers try pulling down the production costs of SLC, or could they somehow make MLC memory behave more like single-level cell NAND?

As implausible as it might seem, the last few months seem to suggest that most companies involved in the enterprise space are choosing the latter path. With drives like Micron's new P400m and Intel's SSD DC S3700 (which we looked at in Intel SSD DC S3700 Review: Benchmarking Consistency), MLC-based offerings are showing up in spaces typically dominated by SLC.

But just as we've seen in the client space, no two enterprise customers are the same. There will always be a place for SLC NAND-based SSDs. Companies like Micron and Intel are instead betting that their affordable MLC-equipped drives can satisfy a majority of situations where pricier SLC-laden drives are currently used out of necessity.

The P400m is the latest addition to Micron's enterprise storage family. It replaces the RealSSD P300, an SLC-based workhorse, finding itself above the low-cost RealSSD P400e, but below the PCI Express-based RealSSD P320h, in Micron's stack.

At launch, the P400m will be available in three capacities: 100, 200, and 400 GB. Expect to pay about $3/GB for the 100 and 200 GB versions, while Micron says the 400 GB version should sell for around $900. These prices are for volume orders, but may change based on demand. The company also plans to sell its P400m family through its distribution channel.

Micron P400m
User Capacity
100 GB200 GB
400 GB
Interface
2.5"  6 Gb/s SATA
Sequential Read
380 MB/s
Sequential Write
200 MB/s310 MB/s
4K Random Read
52,000 IOPS54,000 IOPS
60,000 IOPS
4K Random Write
21,000 IOPS26,000 IOPS
Power Consumption(Active)4 W
5 W
Power Consumption (Idle)
0.75 W
Write Endurance
1.75 PB3.50 PB
7 PB
Encryption
None


When we first saw the P400m's spec sheet, we were immediately reminded of Intel's SSD DC S3700. They both address a similar customer, include high-endurance MLC memory, ship in similar capacities, and bear comparable pricing. Dig deeper, though, and you'll see that they're actually quite different. Because both products strive to satisfy similar segments, they should really go up against each other.

In that context, the P400m does come out of the gate looking a little underwhelming. Intel's SSD DC S3700, which posts sequential and random reads results of 500 MB/s and 75,000 IOPS across all capacities, respectively, should be able to outperform these numbers. As far as write performance goes, the S3700 takes a commanding lead at 200 GB and higher; the P400m looks like it might lead at the 100 GB capacity point.

Great drives aren't determined by their specifications, though. Lets take a closer look at what makes the P400m tick.

2. Inside Micron's P400m SSD

The P400m's insides are pretty standard-looking. On one side of the PCB you find the controller, DRAM cache, some capacitors, and eight NAND packages. The bottom plays host to eight more memory packages.

Each package is composed of 25 nm MLC die manufactured by Micron. And although the company doesn't affix any special marketing terminology to the NAND itself (like eMLC or HET-MLC), company reps make it clear that this isn't the same stuff you'd find in a desktop drive. Micron is using extended-life, enterprise-rated MLC memory in the P400m. It's unique to the company's own SSDs, and not available to other vendors on the open market. 

Again, next to the controller you'll find 256 MB of Micron's DDR3 DRAM (2SD22-D9LGQ). So, all of the P400m's storage is manufactured by Micron.

On the other hand, the controller is a Marvell 88SS9187-BLD2, also found on Plextor's enthusiast-oriented M5 Pro. This eight-channel, dual-core ASIC connects to the host over a 6 Gb/s SATA interface. Even if the controller logic isn't Micron's own, the company did develop custom firmware written to specifically support its MLC NAND. The controller also has dedicated hardware buffers that help accelerate RAID calculations.

All together, Micron enjoys a higher degree of vertical integration than most SSD vendors achieve. What is it able to do with that advantage?

3. Extended Performance And Enhanced Reliability Technology (XPERT)

Any time we talk about a product built using components and technologies from one vendor, we have to consider the advantages of vertical integration. SSD vendors that manufacture the NAND in their drives have an inherent advantage over the companies that buy their memory. This can show up in pricing, in performance, or in reliability. In each case, though, it's only possible to extract those benefits through comprehensive testing.

With its P400m, Micron is hoping to differentiate itself from the competition through a set of enhancements designed to extend the SSD's life and guarantee the reliability of stored data. Some of the comprising features have shown up previously, while others are completely new. Micron calls this collection of storage architecture features XPERT, for eXtended Performance and Enhanced Reliability Technology.

The first feature in XPERT, dubbed Adaptive Read Management/Optimized Read (ARM/OR), is described by Micron as: a dual-faceted data management technique with both proactive and inline protection. In proactive mode, ARM/OR ensures that data stored on the SSD is immediately available by sampling the stored data and dynamically tuning the NAND device in the background. This tuning, based on Micron-specified thresholds, is completely transparent with no effect on drive or system performance. ARM/OR inline mode provides additional protection by making fast and precise foreground tuning when the host reads data from the XPERT-enabled SSD. 

Memory cells change over time, based on wear. If a controller continues to access them the same way during an SSD's life, the point at which you'll start experiencing bit errors will be sooner than if read parameters are adjusted dynamically. ARM/OR runs in the background, sampling the memory and tuning it based on thresholds defined by Micron. This management helps extend the useful life of the NAND, simultaneously allowing the company to use less expensive memory and lowering the total cost of ownership.

The next feature in XPERT is DataSAFE, which Micron says: protects user data as it moves from the host to the SSD interface, through the data path inside the SSD, into the storage media, and back. In addition, DataSAFE embeds the host logical block address (LBA) with the host data before storing both in the drive. Storing this additional information (also known as metadata) helps to ensure that XPERT-enabled SSDs return the exact data requested. In addition, DataSAFE includes error-correcting code, which protects data by adding ECC coverage to the information as it enters the DRAM on the SSD. This also ensures that data is committed to NAND without modification.

The final feature is dubbed RAIN, or Redundant Array of Independent NAND. We last saw this feature in Micron RealSSD P320h Review: A PCIe Drive Capable Of 3.2 GB/s. RAIN is most easily characterized as a RAID 5 implementation across flash channels. In the P400m, the implementation is 15+1, meaning you get 15 elements of user data and one element of parity data.

Looking at the individual components of XPERT, you can see how they all fit together. Micron is using a layered approach to data management. While each feature focuses on separate functional blocks and data paths, they all emphasize data integrity and protection.     

4. Test Setup, Benchmarks, And Methodology
Test Hardware
ProcessorIntel Core i7-3960X (Sandy Bridge-E), 32 nm, 3.3 GHz, LGA 2011, 15 MB Shared L3, Turbo Boost Enabled
Motherboard
Intel DX79SI, X79 Express
Memory
G.Skill Ripjaws Z-Series (4 x 4 GB) DDR3-1600 @ DDR3-1600, 1.5 V
System Drive
Intel SSD 320 160 GB SATA 3Gb/s
Tested Drives
Micron P400m, Firmware: 0200
Graphics
AMD FirePro V4800 1 GB
Power Supply
OCZ ModXStream Pro 700 W
System Software and Drivers
Operating SystemWindows 7 x64 Ultimate
DirectXDirectX 11
DriverGraphics: ATI 8.883
Benchmark Suite
Iometer v1.1.0
4 Workers, 4 KB Random: LBA=Full, Span Varying Queue Depths
ATTO
v2.4.7, 2 GB, QD=4
Custom
C++, 8 MB Sequential, QD=4
Enterprise Testing: Iometer Workloads
Read
Write
512 Bytes
1 KB
2 KB
4 KB
8 KB
16 KB
32 KB
64 KB
128 KB
512 KB
Database
67%
100%
n/a
n/a
n/a
n/a
100%
n/a
n/a
n/a
n/a
n/a
File Server
80%
100%
10%
5%
5%
60%
2%
4%
4%
10%
n/a
n/a
Web Server
100%
100%
22%
15%
8%
23%
15%
2%
6%
7%
1%
1%


The Storage Networking Industry Association (SNIA), a working group made up of SSD, flash, and controller vendors, has produced a testing procedure that attempts to control as many of the variables inherent to SSDs as possible. SNIA’s Solid State Storage Performance Test Specification (SSS PTS) is a great resource for enterprise SSD testing. The procedure does not define what tests should be run, but rather the way in which they are run. This workflow is broken down into four parts:

  1. Purge: Purging puts the drive at a known starting point. For SSDs, this normally means Secure Erase.
  2. Workload-Independent Preconditioning: A prescribed workload that is unrelated to the test workload.
  3. Workload-Based Preconditioning: The actual test workload (4 KB random, 128 KB sequential, and so on), which pushes the drive towards a steady state.
  4. Steady State: The point at which the drive’s performance is no longer changing for the variable being tracked.

These steps are critical when testing SSDs. It’s incredibly easy to not fully condition the drive and still observe out-of-box behavior, which may lead one to think that it’s steady-state. These steps are also important when going between random and sequential writes.

For all performance tests in this review, the SSS PTS was followed to ensure accurate and repeatable results.

All tests employ random data, when available. Micron's P400m does not perform any data compression prior to writing, so there is no difference in performance-based data patterns.

5. Results: Write Endurance

We typically spend a lot of time evaluating write endurance when we review enterprise-class SSDs. Write endurance is one of the major differentiators separating enterprise and client-oriented drives, after all. As MLC-based storage continues pushing its way into spaces previously filled by SLC NAND, we have to keep a close eye on this difficult-to-benchmark, but still very important variable involved in evaluating solid-state storage.

Micron takes a two-fold approach to ensuring ample write endurance from its P400m. First, it uses 25 nm MLC NAND specifically binned for enterprise purposes. Instead of the 3,000 or 5,000 program/erase cycles you typically get from client-oriented MLC at 25 nm, Micron rates the P400m's memory for 20,000 cycles. Second, Micron uses 70% over-provisioning across all of the P400m's available capacities. Taken together, the 300 GB model should endure 3.5 PB of data written to it over the course of its life. Put differently, Micron says you can write the drive's capacity 10 times per day for five years. 

As always, we perform our tests using sequential workloads with large block sizes. This reduces the impact of write amplification and wear leveling, giving a better indication of actual P/E cycles for the NAND.

Endurance Rating
Sequential Workload, QD=1, 8 MB
Micron P400m
Intel SSD DC S3700
NAND Type
Micron 25 nm MLC
Intel 25 nm HET-MLC
RAW NAND Capacity
340 GB680 GB
264 GB
IDEMA Capacity (User Accessible)
200 GB400 GB
200 GB
Over-provisioning
70%70%32%
P/E Cycles Observed (IDEMA)
34,195
34,195*36,343
P/E Cycles Observed (Raw)
20,113
20,113*27,532
Host Writes per 1% of MWI
68.39 TB
136.78 TB*
72.69 TB
$/PB-Written
$87.73
$68.71*
$64.66
*Estimated


When we compare the specifications of Micron's P400m to Intel's SSD DC S3700, they appear nearly identical. Both products are said to sustain 10 full writes per day for five years. The 200 GB models from both families specify between 3.5 and 3.65 petabytes of total data written to them. At comparable user-accessible capacities (200 GB), we see similar observed P/E cycles (34,000 versus 36,000).

It appears that Intel holds the leads when it comes to write endurance, but Micron compensates by arming its drive with 340 GB of raw NAND (rather than Intel's 264 GB). This is a good academic exercise. However, in the real-world, customers only care about actual performance and actual endurance. In that context, Micron has no trouble keeping pace with its higher level of over-provisioning.

Of course, using over-provisioning to improve write endurance has its drawbacks. In this case, that drawback is cost. Each gigabyte of user-accessible space on the SSD DC S3700 costs $2.35/GB. The P400m will push that closer to $3/GB. When you look at the raw NAND costs, however, the gap disappears; Micron's P400m is $1.76/GB, while Intel's SSD DC S3700 is $1.78/GB. Consequently, when you look at cost per petabyte of data written, the Intel drive maintains a lead.

Although we only tested Micron's 200 GB P400m, we also estimated the 400 GB model's endurance because it's priced lower than the 400 GB competitor from Intel. When you compare 400 GB drives, cost per petabyte written even out, making the 400 GB P400m a worthy alternative to the SSD DC S3700.

6. Results: 4 KB Random Performance And Latency

The good news is that the P400m slightly exceeds its specification of 54,000 IOPS at a reasonable queue depth. The bad news: it’s consistently lower than Intel's SSD DC S3700. At higher queue depths, the S3700 has a 20,000 IOPS advantage.

The story is the same for random writes. While the P400m easily achieves Micron's specifications, it trails the S3700 at all queue depths. The SSD DC S3700 eventually builds a 5,000 IOPS advantage as queue depths increase.

The story changes when we start looking at latency, though. The P400m actually bests the 200 GB SSD DC S3700 in both latency tests. This is a testament to the work Micron put in to optimizing the P400m's firmware. Considering the maximum latencies we saw from both the RealSSD P300 and P400e, this is a vast improvement.

7. Results: Enterprise Workload Performance

Our next set of tests simulate different enterprise-oriented workloads, including database, file server, Web server, and workstation configurations.

The database workload (also categorized as transaction processing) involves purely random I/O. Its profile consists of 67% reads and 33% writes using 8 KB transfers.

Considering our 4 KB results on the previous page, it should come as no surprise that the SSD DC S3700 outpaces Micron's P400m at all queue depths.

The file server workload, which consists of 80% random reads of varying transfer sizes, does offer more of a surprise. The P400m not only holds its own at higher queue depths, but it actually performs better than Intel's drive at lower queue depths.

The Web server (100% read, varying transfer size) and workstation (80% reads, 80% random) workloads put Intel's SSD DC S3700 back in the lead. While the P400m comes within 2,000 IOPS on the Web server workload, it trails by a more notable margin when we subject it to the workstation test.

8. Results: Sequential Performance

The Micron drive outperforms its specification on a consistent basis. But just as we saw in the random access tests, the P400m just can't keep up with Intel's SSD DC S3700. Micron's offering is more than 90 MB/s slower in read operations and 65 MB/s slower in writes.

9. Results: Enterprise Video Streaming Performance

Enterprise video streaming is a demanding workload within the enterprise space. Companies want more HD streams with higher bit-rates and no stuttering. A storage solution well-suited for enterprise-class video delivery has completely different capabilities than something designed for databases. At the end of the day, you're basically looking for exceptional large-block sequential write performance. You also need a high level of consistency that traditionally isn't seen from consumer SSDs. For a more in-depth analysis, take a look at page 10 of Intel SSD 910 Review: PCI Express-Based Enterprise Storage.

Once the drive is in a steady state, we write its entire capacity 100 times. We use 8 MB transfer sizes and a queue depth of four, recording timestamps for each individual write. The graph below reflects 100-point averaging, so that you can better visualize the results.

The P400m really shines in our Enterprise Video Streaming test. Not only are the data points nicely packed around the average, but the only major dip is easily overcome with minimal buffering. Once you surpass the average, the required buffer goes from just a few dozen megabytes to nearly three gigabytes.

When we look at each individual write during the worst-case test run, more than 91% of the writes are in excess of Micron's specification. Zeroing in to the one-second averages, as we did with Intel's SSD DC S3700, the P400m performs admirably (although it cannot beat the consistency we saw from the Intel drive). The SSD DC S3700 gave us 90% of its one-second averages within 99% of the overall average. In contrast, only 65% of the P400m's one-second averages fall within 99% of the overall average.

Micron's P400m does much better if you compare the individual data points to the product's specification instead of overall average. In fact, 99.8% of all one-second averages are higher than this drive's write specification. A few months ago, these results would have been phenomenal. The problem is that Intel's 200 GB contender also achieves its results at a higher throughput.

Threshold
Best-Case Buffer Size
Worst-Case Buffer Size
300 MB/s
8 MB
67 MB
320 MB/s32 MB71 MB
330 MB/s62 MB83 MB
335 MB/s2,970 MB2,979 MB


This type of consistency is what we've been missing from the enterprise SSD market. Micron's P400m and Intel's SSD DC S3700 are two of the most consistent drives we’ve ever tested, and we just so happened to write about both of them within a month. It's probably no coincidence that both vendors are heavily involved in NAND manufacturing and controller firmware optimization.

10. Micron's P400m: Reliable And Consistent; Fast Enough?

The days of 2.5" SSDs based on SLC memory appear to be coming to an end. In the past 18 months, Intel replaced its X25-E with the SSD 710 and SSD DC S3700. Now, Micron is replacing its P300 with the P400m. At the beginning of this piece we asked whether MLC memory technology is mature enough to compete with single-level cell NAND in demanding enterprise environments? Both Intel and Micron, respected drive vendors, seem to be answering that high-endurance MLC NAND is the future of enterprise SSDs.

The P400m is the fastest 2.5" enterprise-oriented drive we've seen Micron introduce. It races past the P300 it replaces, as well as the P400e now positioned lower in the company's product line. Sporting low latencies and consistent performance, this SSD does well in each test we hit it with.

Unfortunately, the most unique characteristics of the P400m aren't easily benchmarked. Micron's XPERT feature suite promises to extend drive life and reliability with data protection at multiple levels through the ARM/OR, DataSAFE, and RAIN technologies. Average customers will never even know those capabilities are working behind the scenes to keep their data safe. With that said, we really enjoy explaining and trying to quantify vendor-specific enhancements, particularly when they're so well-integrated.

  

But this is the point where we have to address the elephant in the room: Intel's SSD DC S3700. Other than our average and maximum latency tests, where the P400m asserts itself compellingly, the Intel drive wins in almost every other performance measurement. In fact, in a number of benchmarks, the SSD DC S3700 simply dominates.

Micron is able to best Intel when it comes to the price of its 400 GB P400m. However, its 100 and 200 GB models are more expensive. Intel also sells an 800 GB model; Micron does not. The 400 GB P400m is a solid alternative to the SSD DC S3700 when you look at cost per petabyte of data written. However, Micron's 400 GB drive performs a lot like the 200 GB version, while the 400 GB SSD DC S3700 keeps up with Intel's faster 800 GB mode.

Compared to its past efforts, Micron arms the P400m with a lot of new technology and decidedly better performance. But do the company's XPERT optimizations and corresponding promise of reliable storage make up for a second-place finish to Intel's SSD DC S3700 in our benchmarks? That's ultimately the question you’ll have to answer when you decide between these two modern drives.