|Introduction and Specifications|
Solid State Drive technology is set to turn the storage industry on its ear; there is little doubt of this. When you consider the intrinsic benefits of anything built on solid state technology versus anything mechanical, it doesn't take a degree in physics to understand the obvious advantages. Consider the vacuum tube in its day before the advent of the transistor and you'll get the idea. Though audiophiles may argue the tube still sounds "warmer" and more natural, you certainly wouldn't even been reading this page, if it were not for solid state technology. As such, it's a natural evolution that obviously, some day, better technology needed to be developed for mass storage.
In comparison to standard rotational media, SSDs offer lower power, complete silence, exponentially faster random access times and extremely competitive read/write throughput, versus even the fastest hard drives on the market today. Moving forward, SSD specifications and performance will improve significantly as well. Though SSDs are still not really considered a "mainstream" consumer storage solution for computing, you can easily see on the horizon that the day is coming quickly when the SSD will completely take over personal computing and eventually even the enterprise markets.
On the following pages, we thought we'd level-set the features, performance and pricing landscape for you with respect to the current state of SSDs. In the coming weeks you'll see a major release from Intel for their new SSD offering as well, so we'll be sure to return to this equation again in the near future. For now, we have a look at four different SSD offerings, two from OCZ, one from Mtron and another from Super Talent. Is a Solid State Disk in your future? We'll try to help you answer that question in this full performance evaluation and showcase.
There are some subtle and not-so-subtle differences in each of the SSDs we're going to step you through today. First, we should point out that we have two SLC-based disks and two MLC-based disks in this round-up, which also means two very distinct sets of price points and reliability. We'll cover this in more detail next. All of our SSDs here are showing sustained read bandwidth north of 100MB/sec, with the Core Series drive from OCZ topping out at 143MB/sec. Write throughput ranges from 80MB/sec to 130MB/sec for the Mtron drive, which is the fastest in terms of claimed write performance. All of the drives have average access times specified at a tenth of a millisecond, which, as you can imagine, is lighting-fast compared to even the fastest spinning hard drives out there, which top out at 3 - 4ms.
Finally, as you'll notice, if you compare Super Talent's write endurance spec to Mtron's, SLC-based drives have significantly longer life expectancies. We'll dive into the major differences between SLC and MLC-based flash media next.
|SSD Technology And Our Competitors|
Before we dig into the specifics of the products we've tested for you here today, let's take a quick look at the anatomy of a typical Solid State Drive. Though you may dismiss an SSD to be nothing more than a bunch of memory chips plunked down on a PCB, in reality a Solid State Disk, like a standard hard drive, is a bit more complex. Below is a block diagram, courtesy of Mtron, that shows the topology of their SLC-based (Single-Level Cell) SSD.
SLC SSD Block Diagram - Courtesy: Mtron Technology
Mtron's MSP 7500 series of Solid State Disks are built with a proprietary multi-channel parallel array memory controller that affords the product its snappy sustained read/write specs of 130MB/sec and 120MB/sec respectively. As you can see, the design incorporates an ARM7 based control processor with associated SRAM cache, as well as an SDRAM buffer cache for the host interface, similar to a standard hard drive. This storage subsystem also provides the drive both static and dynamic wear-leveling, which ensures the use of the drive's memory evenly to extend the products usable life, as well as ECC and bad block management. Unfortunately, this, in addition to its SLC NAND flash memory, also adds considerable cost. The Mtron MSP 7500 Pro series drive is actually the most expensive in our round-up, currently at $779 for its 32GB capacity. Hence its "Pro" moniker, which calls attention to the fact that this drive is targeted for industrial or more mission-critical applications that require high reliability as well as performance.
OCZ Core Series MLC-based SSD - Component Side PCB
On the other end of the spectrum, we have OCZ's Core Series SSD, which is an MLC-based (Multi-Level Cell) design and typical of most MLC-based SSDs. As you can see in the picture above, the drive has Samsung MLC flash chips, a few passive components and a single JMicron SATAII to Flash controller. It too offers a host interface for the flash array as well as wear-leveling technology and ECC (error correction) and bad block management. The primary differences between MLC and SLC-based SSD designs, are cost, density and life expectancy. For example, the Mtron SLC drive has a specified 140+ year write endurance at 50GB writes per day. Conversely, Super Talent specifies their MasterDrive MX MLC drive at 32 years write endurance for 50GB/day. More on this, next.
Of SLC and MLC -
As we mentioned earlier, there are currently two types of flash technologies that SSDs are built on, SLC and MLC. In short, you can think of the SLC type as higher quality with higher reliability but also lower density and a lot more expensive. SLC flash stores a single bit value per cell (either a 1 or 0), while MLC has four prommable states; 00 for fully programmed, 01 for partially programmed, 10 for partially erased and 11 for fully erased. This quick table, courtesy of Super Talent, tells the story nicely, at least at the chip level.
As you can see, MLC flash offers 2 - 4 times the density of SLC but significantly lower endurance, by a factor of ten, in terms of its available number of write cycles. You'll also notice that SLC has a slightly faster read speed but the memory controller used in the SSD also plays a big factor. Probably the most significant difference at the chip level is SLC's block size, which is much more granular at half the size of MLC and it's part of the reason why small block erase/re-write speed with SLC flash is faster. In addition, SLC type SSDs generally incorporate DRAM and/or SRAM cache buffers, which also afford them some performance advantages in certain scenarios. However, all of this aside, it's safe to say that, due to its cost factor alone, SLC-based SSDs will remain as enterprise or industrial type products, while MLC-based SSDs will become pervasive for the mainstream consumer market.
Courtesy: SuperTalent Technology, Inc.
Now that you're armed with some background on flash SSD technologies, we'll get down to specifics with each of the products in our round-up today. We'll be looking at performance with two SLC-based drives, one from Mtron and one from OCZ, as well as two MLC-based drives from OCZ and Super Talent.
Mtron MSP 7525-032 Pro Series 32GB SLC - MSRP $779
OCZ OCZSS02-1S64G 64GB SLC - $695 after mail-in rebate
OCZ Core Series 64GB MLC - $214 after mail-in rebate
Super Talent MasterDrive MX 64GB MLC - $196 after mail-in rebate
There really aren't any physical attributes that would help you distinguish one type of SSD over the other, with the exception of the manufacturer's casing design and labeling. In fact, none of the drives we've tested here today were even marked as an SLC or MLC based product. About the only way you can distinguish one technology over the other, is by its price point. Another interesting datapoint is the capacity label on some of the drives. For instance, Super Talent labels their SSD a 60GB product, while OCZ labels their drives 64GB, which is a more common multiple for memory obviously. In reality, formatted usable space for a 64GB flash SSD is about 56.33GB.
|Our Test System And SANDRA Testing|
|Our Test Methodologies: Under each test condition, Solid State Drives were installed as secondary volumes in our testbeds,with a standard spinning hard disk for the OS and benchmark installations. SSDs were left blank without partitions wherever possible, unless a test required them to be partitioned and formatted. as was the case with our ATTO benchmark tests. Windows firewall, automatic updates and screen savers were all disabled before testing. In all test runs, we rebooted the system and waited several minutes for drive activity to settle before invoking a test.
Why No IOMeter? Though we struggled for several days with IOMeter, in an effort to get consistent, repeatable results, in the end we were not satisfied that our IOMeter test procedures were producing an accurate measurement of solid state disk drive performance. Additionally, though IOMeter is good for establishing multi-user and multi-node performance (networking) of a drive, it has little bearing on single user measurements. Certain anomalies were observed during our testing which we believe were related to the fact that we were testing on Windows Vista. We are currently working with manufacturers to better understand our results and ways we can make use of IOMeter for testing in future SSD technology-related articles in the coming weeks.
In our SiSoft SANDRA testing, we used the Physical Disk test suite. We ran the tests without formatting the drives and both write and read performance metrics are detailed below. Please forgive the use of these screen captures and thumbnails, which will require a few more clicks on your part. However, we felt it was important to show you the graph lines in each of the SANDRA test runs, so you are able to see how the drives perform over time and memory location and not just an average rated result.
SANDRA Physical Disk Read Performance
In our read performance test with SANDRA, the OCZ Core Series drive offered the fastest sustained read bandwidth at 117.11MB/sec, followed closely by the 32GB Mtron drive at 116.55MB/sec and the Super Talent 64GB drive at 110MB/sec. The OCZ 64GB standard SLC drive followed the pack some 25% slower at 93.33MB/sec. In all tests, read performance was very flat and robust across all SSD volumes. On a side note, notice how the WD VelociRaptor reference score in SANDRA (green line) maps in at about the same level as the standard SLC drive from OCZ and significantly below the OCZ Core Series, Super Talent MasterDrive MX or Mtron drives.
SANDRA Physical Disk Write Performance
As we expected, write performance characteristics were a bit more interesting. All of the SSDs, with the exception of OCZ's 64GB SLC drive, showed significant saw-tooth patterns with big dips and spikes in performance. This happens most likely due to chip boundaries and transitions as the benchmark attempts to write sequentially across the volume. The Mtron and OCZ SLC drives exhibited the best performance with respect to writes, due to their on-board DRAM and SRAM cache, which helps mitigate some of these chip transitions.
|ATTO Disk Benchmark|
ATTO is a more straight-forward type of disk benchmark that measures specific transfer sizes across a specific volume length. It measures raw transfer rate for both reads and writes and graphs them out in an easily interpreted chart. We chose 8kb through 1024kb transfer sizes over a total max volume length of 32MB. This test was performed on blank, formatted drives with NTFS partitions.
Again, our apologies for all the thumbnails but as we've said before, the pictures speak volumes. A few obvious observations we can easily take away are that all of the MLC-based SSDs had a tougher time with small block writes from 8K - 32K and didn't become competitive with the SLC-based drives or the VelociRaptor, until we hit the 64K transfer size threshold. At that point, the Core Series OCZ and Super Talent drive held their own, though, in general, they did fall a little short on write performance versus the others. And there's no question, the VelociRaptor 10K RPM hard drive smoked all SSDs in this test, in terms of write performance. From a read perspective, the MLC-based OCZ and Super Talent drives outpaced even the VelociRaptor in large file transfers but lagged behind it in small 8K - 32K transfers yet again. Finally, performance with the SLC-based SSDs was significantly flatter and more deterministic versus the MLC-based product. The SLC drives had fewer spikes and dips exhibited depending on transfer sizes but generally offered less throughput overall versus their MLC siblings.
Simpli Software's HD Tach is described on the company's web site as such: "HD Tach is a low level hardware benchmark for random access read/write storage devices such as hard drives, removable drives, flash devices, and RAID arrays. HD Tach uses custom device drivers and other low level Windows interfaces to bypass as many layers of software as possible and get as close to the physical performance of the device possible."
As you'll note, with all the jagged saw-toothed lines in the OCZ Core Series and Super Talent MasterDrive MX graphs, MLC technology has a lot more variability in performance over its volume, though unlike the VelociRaptor spinning drive, performance doesn't degrade as you get out to the farther reaches of the drive. Again, if we think of read/write operations, as they span over chip-level boundaries, you can see how these transitions map out in terms of performance peaks and valleys. The SLC-based Mtron and OCZ drives again showed much smoother transitions due to their on-board cache buffers but again they also cost over three times as much as an MLC equivalent. Regardless, the OCZ Core Series drive offered the highest average read throughput of 119MB/sec, followed by the Mtron and Super Talent drives in a close second and third place.
Of course the VelociRaptor once again reined supreme for write performance but the OCZ Core Series and Super Talent MasterDrive MX put up solid numbers in the mid 70s. And if you've been paying attention, you'll probably note that the OCZ Core Series and Super Talent MasterDrive MX drives, both here and in the ATTO and SANDRA tests, put up strikingly similar performance characteristics in each location of their volumes. It's safe to say that these are likely very similar drives from a hardware standpoint, with only small modifications in firmware setting them apart. Finally, look at the Mtron drive's absolutely linear performance across the entire test, along with its zero CPU utilization. This is what a custom storage controller and cache subsystem can do to maximize SSD drive performance.
|PCMark Vantage HDD Test|
Next up is PCMark Vantage from FutureMark Corp. We specifically used only the HDD Test module of this benchmark suite to evaluate all the drives we tested. Feel free to consult Futuremark's white paper on PCMark Vantage for an understanding of what each test component entails and how it calculates its measurements. For specific information on how the HDD Test module arrives at its performance measurements, we'd encourage you to read pages 35 and 36 of the white paper.
The obvious first take-away here is that all of our SSDs completely eclipse the WD VelociRaptor in all of these tests. This is largely due to the SSD drive's lighting fast sub-millisecond random access and seek times that are orders of magnitude faster than any spinning disk. And let's face it, the average end user desktop experience is combination of a lot of random read/write operations, with a heavier emphasis on reads. The average SSD score here offers two to three times the throughput of the 10K RPM VelociRaptor, in terms of Windows Vista start-up performance. From there, the rest is self-explanatory. Overall, the lower cost MLC-based OCZ Core Series and Super Talent MasterDrive MX offered highly competitive performance versus their Cadillac-priced SLC cousins.
|PCMark Vantage HDD Test Continued|
Our next series of Vantage tests will stress the current Achilles Heel of all SSDs, that being write performance. Applications like video editing, streaming and recording are not what we would call a strong suit for the average SSD, due ot their high mix of random write transactions. We should also note that it's not so much a weakness of the memory itself, but rather the interface and control algorithms that deal with inherent erase block latency of NAND flash. SSD manufacturers are getting better at this but still today, especially with consumer grade SSDs, spinning drives still have the edge with respect to write intensive applications.
If we were to hand out an all-out real-world performance award, it would have to be to OCZ's 64GB standard SLC drive. It consistently showed top-of-the-line performance and very few soft spots, even within the Vantage Windows Media Center and Movie Maker tests, which are comprised of nearly 50% write operations. Beyond that, the OCZ Core Series and Super Talent MasterDrive MX SSDs continue to mirror each other's performance. The MLC drives and Mtron's SLC drive can't keep up with the VelociRaptor in the Media Center tests but fare a little better in the Movie Maker test, where video read and skip operations afforded them a bit more performance headroom. Finally, again, if you look at more read intensive tests, like application loading with Microsoft Word, Internet Explorer, Adobe Photoshop or MS Outlook, as well as the Windows Media Player tests, the SSDs overtake the speedy WD VelociRaptor, in some cases by an order of magnitude.
Although hard drives don't typically draw huge amounts of power, we still wanted to see how this new breed of SSDs compared to WD's VelociRaptor 10K RPM hard drive, in terms of power consumption. Throughout all of our benchmarking and testing, we monitored how much power our test system was consuming using a power meter. Our goal was to give you all an idea as to how much power each configuration used while idling and under load. Please keep in mind that we were testing total system power consumption at the outlet here, not just the power being drawn by the drives alone.
|Performance Analysis and Conclusion|
Performance Summary: Overall, when we look back at our benchmark data, our SSD test candidates as a whole offered higher average read bandwidth and generally competitive write bandwidth, though definitely not as robust with small file writes in the 4K - 32K range. That said, most end user scenarios generally aren't write intensive with small file sizes below 64K. If you're storing a bunch of low resolution pictures, for example, you might notice a performance differential but these days, file sizes certainly aren't shrinking. The write performance limitation of current SSD technologies would likely manifest itself in database server applications under transactional conditions, though we didn't prove this out in our testing due to the issues we saw with IOMeter and SSDs under Vista. We'll be revisiting this test setup under Windows XP in the days ahead, as we look at next generation SSD technology that is coming to market from other major OEMs.
We should note however, that there are still a few caveats with SSDs that the informed consumer should consider. First, in general there have been moderately high failure rates with some of the earlier version SSD MLC technologies, with reports of both data corruption and loss, so make sure you look at warranty coverage for any product. And as always, protect your valuable data with daily backups. In addition, it has been widely reported that the Windows Vista operating system exhibits performance issues with SSDs under certain conditions, due to inefficient handling of data over an SSD's 4K page or sector size, versus a traditional hard drive's 512-byte sector size. Major OEMs like Samsung are reportedly working on the problem with Microsoft, so hopefully things will getting better for SSDs and Vista in the not-so distant future. While it certainly may make sense to hold off on a major SSD investment until things mature a bit more for SSD technologies, we do feel 2008 will likely go down as "the year of the SSD".
OCZ 64GB Standard SLC SSD: The OCZ 64GB standard SLC-based SSD we tested actually proved to be another interesting and compelling option, due to its highly stable and consistent performance for both read and write operations. This drive showed significantly less variation in random write performance over small file sizes, though it didn't top out quite as high in read performance versus the other drives in our round-up. The real issue with this SSD for the average end user will be its price. It's the second most expensive drive of the bunch at $695 after mail-in rebate. It's likely that most folks won't be able to justify its $10/Gig cost structure. In general, these types of SLC-based SSDs will cater to the performance enthusiast and enterprise applications in the future, while MLC-based products will continue to mature as a mainstream offering.
Super Talent MasterDrive MX 60GB MLC SSD: The Super Talent MasterDrive MX was an interesting product in that it mirrored the OCZ Core Series SSD in nearly every test, though it was also consistently slightly behind it in all our benchmark scores. And frankly, Super Talent's specifications of the drive were a bit more conservative versus the OCZ Core Series product, with the MasterDrive MX able to hit closer to its specified read/write speeds of 120MB/sec for reads and 80MB/sec for writes. Super Talent does also offer a 3-year warranty as well, which is a bit better than OCZ's 2-year policy. In the end, though it didn't offer quite as much peak performance as the OCZ Core Series, it's also currently the cheapest drive of the group we tested at $196 dollars via NewEgg after mail-in rebate. And you can be sure that overall prices will continue to decline for SSDs, so make sure you cross-reference the competitive landscape on a regular basis.
Mtron MSP 7500 Pro 32GB SLC SSD: The Mtron SLC-based MSP 7500 Pro was a bit of a mixed bag for us. On one hand it offers extremely stable read/write performance across its entire volume, exhibiting far less variability versus the other SSDs and even the WD VelociRaptor 10K RPM hard drive. It also offered near-zero CPU utilization with its on-board control processor, SRAM and DRAM cache subsystems. However, though its read performance clearly fell into the top-end for our round-up, with the drive coming close to the OCZ Core Series performance numbers, the MSP 7500 Pro's write performance was the worst of the bunch by a fairly significant margin in many tests and it was obvious in our PCMark Vantage testing. Finally, this drive is far and away the most expensive of the group, weighing in at a hefty $779 MSRP currently for only a 32GB density. In reality, the MSP 7500 Pro is probably better suited for industrial or enterprise applications, where deterministic performance and reliability is much more critical. Mtron also brands this drive with "24/7 reliability", which is something you traditionally do not see highlighted currently with most SSDs. We'd feel most comfortable with this drive in server environment, which is something we probably wouldn't advise with the other MLC-based drives in our round-up. Mtron also offers a 5-year warranty on this drive, which is the best of the lot that we tested.