|Introduction and Specifications|
|A couple of years back we attended an IDF event in San Francisco, and among other disclosures, behind closed doors the company was showing off a PCI Express-based SSD with current generation Intel NAND Flash and based on an array of SandForce controllers. As it turns out, that product never saw the light of day and was more of a demonstration and proof of concept vehicle for Intel than anything else. We've heard rumblings of Intel PCI Express SSD devices since then but nothing materialized until very recently when Intel stepped out with a full-fledged product announcement of their SSD 910 family of Solid State Drives.
Of course, with the significant traction PCI Express SSDs have started to gain in the market, it was about time Intel offered up a solution of their own. In this arena, though there have been a few "prosumer" or high-end workstation-targeted solutions launched from the likes of OCZ and Fusion-io, the large majority of products in this class of SSD are targeted to the Datacenter and the Enterprise. The Intel SSD 910 is definitely in the latter camp. With an MSRP of $1929 for 400GiB of capacity and $3859 for an 800GiB card, even mainstream performance enthusiasts would have a hard time justifying the cost, though at about $4.82 per GB you could see a high-end workstation professional, with large datasets to crunch, making the justification perhaps.
That said, as you'll see in the pages ahead, where the new Intel SSD 910 really excels is in datacenter applications with literally thousands of concurrent IO requests that would otherwise wreck havoc with lower bandwidth solutions.
** MSRP: 400GB - $1929; 800GB - $3859
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First things first. If you're a specification scanner that doesn't like to read beyond checkbox items like IOPS, we'll point out that those performance numbers are measured on a full LBA span of the drive. We actually saw significantly better numbers as you'll see in the benchmark data ahead.
What's perhaps more interesting is the max sustained read/write bandwidth of the SSD 910, at 2GB/sec and 1GB/sec, respectively. Intel also offers a high performance mode for the SSD 910, which can be toggled in software, that increases the card's power draw but also increases write bandwidth to a max of 1.5GB/sec. On paper, the product competes with some of the fastest PCI Express SSD solutions on the market, though it can't quite match OCZ's Z-Drive R4, which notably is quite a bit more expensive ($4599 for 800GiB currently) than the Intel product.
Finally, if you weren't looking closely enough, what may have sneaked past you are the SSD 910's Lifetime Endurance specifications. You're reading the numbers correctly; that's 7 Petabyte and 14 Petabyte endurance for the 400GiB and 800GiB drives, respectively. Intel claims up to 10 full drive writes a day for 5 years, which is a 30x improvement over the company's standard SATA SSDs.
So you get the drift; blinding speed, yes, but enterprise-class, mission critical endurance to go with it. Lest we digress any further, let's dig into the intimate details of Intel's new SSD 910 PCI Express Solid State Drive.
|A Detailed Look at The Intel SSD 910|
|The Intel SSD 910 is a surprisingly elegant design. There are three PCBs that make up the half-height card that will likely fit cleanly into many low profile server designs. The card's width consumes only a single PCI Express slot, though it is a fairly dense design that requires adequate airflow.
In fact, Intel specifies a required 200 LFM (Linear Feet per Minute) air flow over the device with a 0 - 55ºC ambient operating temp range. In other words, you're not sandwiching this bad boy between two piping hot graphics cards or in a dense server configuration, without direct airflow pointing right at the card. 200 LFM isn't exorbitant (it's a fairly standard server airflow spec) but fair warning. Keep 'er cool.
Yes, we were crazy enough to tear down a $3800 SSD; verrrry carefully. Click for high res.
Intel SSD 910 High Level Architecture
The tear-down shot above (no worries, precious wasn't injured in the process) and the block diagram here give us a good idea of how the device is configured and how it operates. The 800GiB Intel SSD 910 we tested is made up of four SSD modules, 200GiB for each module, though they're populated across two PCBs, each with 448GB of Intel 25nm NAND per card (over-provisioned). Each of the SSD arrays is managed by a co-developed Intel-Hitachi SAS/NAND controller. Each of these controllers is a dual-core chip with its cores managing either the SAS or NAND interface. If you look closely, each of these controllers is also flanked with a pair of Micron DDR2 SDRAMs.
Then, providing a X8 Gen 2 PCI Express link to the card edge is an LSI 2008 (PDF) PCI Express to SAS bridge. This SATA/SAS controller (under the silver heat sink) has been on the market for some time with widespread driver support. At its heart is a 533MHz PowerPC 440 processor but unfortunately the Intel implementation doesn't offer hardware RAID support. In fact, each of the 200GiB SSD modules will present as a separate volume to the operating system. In addition, the SSD 910 is not bootable. You can, however, configure an 800GiB (or 400GiB for the lower capacity drive) software RAID 0 array with the card, so you can aggregate performance across all SSD controllers. This is the exact configuration we tested it in.
Speaking of which, let's fire it up...
|Test System, SANDRA Physical Disk and FIle System|
Our Test Methodologies: Under each test condition, the SSDs tested here were installed as secondary volumes in our testbed, with a standard spinning hard disk for the OS and benchmark software installations. The 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, Vantage, and CrystalDiskMark benchmark tests, as well as IOMeter runs. 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.
** Please also note that the Intel SSD 910 card was configured in high performance mode, for maximum write performance of up to 1.5GB/sec.
For our first set of tests, we used SiSoft SANDRA, the the System ANalyzer, Diagnostic and Reporting Assistant. Here, we used the Physical Disk test suite and provided the results from our comparison SSDs. The benchmarks were run without formatting on all drives and read and write performance metrics are detailed below.
SANDRA's purely sequential and rather short read/write tests show the Intel SSD 910 bringing up the rear by a notable margin. In this test, SANDRA only sees each individual 200GB SSD module on the card, even if we format and RAID the drive in Windows. As a result, what you're seeing here is essentially about 25% of the total available bandwidth for the SSD 910. Doing the math, optimally across all volumes, the Intel PCIe SSD should offer 1.6GB/sec for reads and 1.2GB/sec for writes
(Note: In SANDRA's File System test, which exploits the software RAID setup, the Intel drive offered up 1.7GB/s--more results forthcoming).
We'll see if that pans out in other tests that can exercise the drive across all of its SSD modules simultaneously as well.
|AS SSD Benchmark Tests|
Next up we ran AS SSD, an SSD specific benchmark being developed by Alex Intelligent Software. This test is interesting because it uses a mix of compressible and incompressible data and outputs both Read and Write throughput of the drive.
With this test we had fewer reference datapoints to compare in short order for this review. So we picked one of the stiffest all around competitors we could find, Fusion-io's ioDrive 160GB card. Note that sequential and 4K random read/write throughput of the Intel SSD 910 is approaching theoretical max performance numbers for the product and it crushes the Fusion-io drive. However, when it comes to access latency with very small file transfers the Intel SSD 910 trails by a factor of 5. Keep this in mind as we look at other benchmark data in the pages that follow.
CrystalDiskMark is a synthetic benchmark that tests both sequential as well as random small and large file transfers. It does a nice job of providing a quick look at best and worst case scenarios with regard to SSD performance, best case being larger sequential transfers and worse case being small, random access and transfers.
CrystalDiskMark does a really nice job of exploiting the strengths and weaknesses of Intel's new PCIe SSD solution. On top, we see the drive's pure sequential performance competes with the likes of OCZ's Z-Drive R4, even edging it out in overall write throughput. However, drop that files size down to 512K and read throughput takes a nosedive, though still fairly robust with write throughput unaffected. Drop down to a tiny 4K transfer with a shallow queue depth and the Intel SSD 910 takes a knee. Conversely however, scale up to a queue depth of 32 with that same 4K transfer payload and Intel's SSD 910 earns top marks. It's here that we begin to see just how this new PCI Express solution from Intel is tuned. In short, when all SSD controller resources on the drive are exercised, the SSD 910 will stretch its legs. A client-tuned SSD this product surely is not. The SSD 910 appears to be tuned for big iron workloads and access patterns.
|IOMeter Test Results|
As we've noted in our previous SSD coverage, though IOMeter is clearly a well-respected industry standard drive benchmark, we're not completely comfortable with it for testing SSDs. The fact of the matter is, though our actual results with IOMeter appear to scale properly, it is debatable whether or not certain access patterns, as they are presented to and measured on an SSD, actually provide a valid example of real-world performance for the average end user. That said, we do think IOMeter is a gauge for relative available bandwidth with a given storage solution. In addition there are certain higher-end workloads you can invoke on a drive with IOMeter, that you really can't with any other benchmark tool available currently.
In the following tables, we're showing two sets of access patterns; our Workstation pattern, with an 8K transfer size, 80% reads (20% writes) and 80% random (20% sequential) access and our Database access pattern of 4K transfers, 67% reads (34% writes) and 100% random access.
As we saw in a few of the previous benchmarks, random read performance is not the SSD 910's strong suit. It's only as the IO queue depth begins to scale that Intel's solution starts to join the hunt.
Our database access pattern showed much of the same performance grouping as we saw in the Workstation setup. However, with a higher write workload and smaller 4K transfers, the Intel SSD 910 begins to show signs of strength. Still Fusion-io's ioDrive and OCZ's Z-Drive far and away lead the pack in this test pattern.
The workload you see represented in this graph has become a bit "industry standard" as of late, though we'd offer that it still should be taken with a grain of salt. Again, what we're looking at here is one set access pattern that is concurrently sprayed across the drive volume by IOMeter until the drive reaches its saturation point. In this IOMeter run, we should note that drives were formatted, blank and were allowed to sit idle for several hours before invoking a test, so that each drive's maintenance algorithms had a chance to maximize performance.
This access condition is clearly where Intel's SSD 910 shines. We didn't have access to the OCZ Z-Drive R4 here unfortunately but we'd offer it would likely be a close race. With a full write-only workload, small transfer sizes and a high queue depth, the Intel SSD 910 actually takes the top spot here by a comfortable ~ 15% margin.
|ATTO Disk Benchmark|
|ATTO is another synthetic disk benchmark that measures transfer speeds across a specific volume length. It measures raw transfer rates for both reads and writes and graphs them out in an easily interpreted chart. We chose .5kb through 8192kb transfer sizes and a queue depth of 10 over a total max volume size of 256MB. ATTO's workloads are sequential in nature and measure raw bandwidth, rather than IO response time, access latency etc. This test was performed on blank, formatted drives with default NTFS partitions in Windows 7 x64.
In our ATTO testing, the Intel SSD 910 offers up an admirable performance curve, in line for the most part with its datasheet specifications for raw read/write bandwidth. The SSD 910 actually out-performs all other solutions here with the exception of OCZ's Z-Drive R4 product, which is able to push close to the 3GB/sec mark for reads and well in excess of 2.5GB/sec for writes in this test. We think of ATTO as sort of a best-case test condition for most storage solutions around here; so think of these plots as pretty much the best foot forward for each of the products we tested.
|Performance Summary and Conclusion|
|Performance Summary: Intel's 800GIB SSD 910 PCI Express SSD offered solid performance under most test conditions, while occasionally offering break-out numbers under higher queue depth workloads, as we saw in our CrystalDiskMark and some IOMeter tests. In our ATTO benchmark test, the SSD 910 was the second fastest card we've tested to date, only exceeded by the more expensive OCZ Z-Drive R4. Write performance was especially strong for Intel's new PCIe SSD, where the drive even occasionally edged-out the OCZ product.
Intel's PCI Express-based SSD 910 is an interesting storage solution. Clearly, the product is tuned for very specific usage models, primarily those found in datacenter server environments or other high concurrent transaction rate, enterprise applications. Further, the SSD 910 also isn't really tuned to handle high-end workstation requirements, though in some cases its sequential transfer speeds could be attractive. To use a completely worn-out cliche', the Intel SSD 910 is aiming for the "cloud."
Over-used, marketing buzz words aside, the Intel SSD 910 demonstrated performance characteristics that we feel position the device as a very promising solution for high endurance datacenter server use. At under $5 per GB, the device is actually reasonably priced for a PCI Express SSD, relatively speaking. Performance with Intel's SSD 910, under high queue-depths with a healthy mix of write transactions, as you'd see in a typical database server workload, is excellent. And with a 7 - 14 Petabyte Lifetime Endurance figure, with wear leveling across all NAND modules, there's really no way to point at this storage subsystem as being a significant point of failure risk, at least no more so than other subsystems in your environment.
The only real letdown for us, is the drive's lack of on-board hardware RAID, requiring a software RAID implementation for any setup currently. And of course, it would be nice if the SSD 910 was bootable, though admittedly, you certainly can find more useful things to do with this high-end SSD, beyond running an OS on it.
Regardless, with Intel's track record in SSD reliability, we can see the SSD 910 enjoying a pretty robust uptake curve in the enterprise and datacenter arenas, once the company has seeded enough of these boards in the market for environment and life testing. It's good to see Intel with a bit of skin in this game. Might we see workstation or "prosumer" solutions next?
Intel SSD 910 800GB PCI Express SSD