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HD Overdrive: Corsair's Accelerator SSD Cache
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Date: May 18, 2012
Section:Storage
Author: Joel Hruska
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Introduction
Solid State Drives are a fabulous way to boost a system's performance, but for all their strong points, they aren't an easy upgrade for a lot of people. Performance can vary significantly between manufacturers, only the most expensive drives can replace the need for an HDD in an enthusiast / data-heavy system, and reinstalling a full suite of software from scratch is a major headache.

Corsair's Accelerator Series family of SSDs is designed to reduce the barriers to the SSD option by offering a solution that's accessible without the need to wipe your existing HDD or create a storage plan that ensures you make the best possible use of a small SSD, while leaving the bulk of your data on a rotating platter. With a cache accelerator, you can theoretically enjoy the best of both worlds. This is made possible thanks to specialized caching algorithms developed by Nvelo. Their software, dubbed Dataplex, monitors the data a user accesses on the HDD and caches commonly used bits of data to boost performance.

Corsair claims that "Using an Accelerator Series solid-state cache drive can boost your system's read and write performance up to 5x compared to using a hard drive alone. Just add the cache drive to your system, download and install the intelligent caching software, and start enjoying faster boot times and quicker file access." We'll investigate how well such claims hold up in the real world.


Installation and Registration
Corsair ships the drive with a 2.5" to 3.5" bay adapter and some mounting screws, but you can't just drop the new drive in your system and call it quits. First, you have to turn the drive over and write down the 28 character alphanumeric code. There's no prominent sticker that points this out, and while it is mentioned in the installation guide, we'd wager a fair number of enthusiasts don't bother to consult such literature when installing something as simple as an SSD. It doesn't help that the code is on the bottom of the disk and looks, at first glance, like a serial number.



Corsair's booklet instructs you to write the code inside the manual. Said manual is printed on glossy paper, which makes writing with pencil an exercise in futility; most ink will simply smear. We recommend writing the code on actual paper and think Corsair should've included a peel-off sticker.

Windows detects the SSD as a standard 60GB drive. At this point, you visit Corsair's website and download the software package. The key code has to be entered at two separate points -- once at Corsair's website, and once during the driver installation process. After that, the system reboots and the drive vanishes. It's even invisible to the Device Manager and the storage management utility inside Windows' Administrative Tools. There's a small, DOS-based status utility embedded in the Dataplex folder inside the Start Menu for checking drive status, however.



That's it. There are no user-configurable settings of any kind and currently no drive health monitoring utility.
 
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The (Considerable) Fine Print.
There are two types of fine print to discuss here. The first relates to license restrictions on the software, the second is the limitations on hardware.

License Restrictions:
There are some restrictions to the Dataplex software that are currently only listed OCZ's website -- Corsair hasn't added them. It states:
Disclaimer: Your Dataplex licensing key is only valid on one machine. Dataplex uses various components to identify a PC (memory, OS, CPU Id, BIOS, Ethernet card); if two or more components change, it is considered a different machine. If you wish to change only one component, Dataplex will automatically revalidate the license as long as there is an internet connection when the PC is rebooted. You must uninstall Dataplex to release the license prior to changing two or more components in your system. Licenses cannot be released after the system is no longer valid.
The reason we're quoting an OCZ disclaimer in a Corsair review is that, according to Nvelo, the same restrictions apply to Corsair customers. What this means is that if you change out too many components, your system may want to revalidate the driver. The  method of re-validation isn't clear -- presumably it means re-entering the same key code and having an active Internet connection.

Combined with the double-entry software code, this tips over the edge from annoying DRM to bad business decision. Nvelo's Dataplex software is legitimately great; it's the reason we now have a new use for SSDs that gives customers access to many of their benefits without the downsides or headaches. What the company is doing, however, isn't security—it's security theater.


Looks an awful lot like this

The term, coined by Bruce Schneier, describes security countermeasures designed to make people feel secure without doing anything to improve security. You've mandated the use of a product activation code -- normally a mechanism used to secure software -- and applied it to hardware. There are two massive flaws in this. First, it confuses the heck out of your customers, who are unused to having to provide a serial number in order to use hardware they've legally purchased. Forcing users to enter it twice is pointless--if I've got a code, I've got a code. Double-checking the same validation approach doesn't actually add security. Second, there's literally no logical reason to attach an activation code to a software product that needs hardware to function.



Without an appropriate SSD, your software is useless. The driver files Corsair provides already check to ensure a Corsair Accelerator SSD is installed. Since the Accelerator Series is reasonably priced compared to other 60GB SSDs, and given that few people have piles of old SSDs around that they aren't using, the group of users who might pirate and benefit from your software is extremely low.

Hardware Restrictions:
  • The target drive must be the primary boot drive. Only that drive can be cached.
  • Only MBR (Master Boot Record) partitions are supported. GPT partitions are not supported.
  • Due to the above, the Dataplex software can only be installed on a 2TB or smaller HDD.
  • The Windows system partition (the 100MB partition Vista and Windows 7 carve out at installation time) must be on the same HDD as the C:\Windows folder.
  • Multiple OS's are not supported.
  • Only one cache drive per system.
  • The cache drives cannot be RAIDed. A RAID array of mechanical HDDs can be interfaced with a Corsair Accelerator drive.
  • Once installed, the Dataplex software must be uninstalled properly before the drive is removed from the system. Failure to follow this procedure can result in a loss of data. An HDD synchronized with an Accelerator cache drive may not boot properly if the cache drive is suddenly removed.
Almost all of these criteria are corner cases. The one point that isn't a corner case, and that Nvelo unfortunately has no intention of addressing, is the users' total lack of control over what the drive caches and how data is evicted from the disk. Since the company's current drive information utility is lacking (to put it kindly), we asked whether updates to the drive status software or any degree of configurable control is in the works. According to Nvelo's David Lin:
It [the Dataplex software] is a Windows block-level filter driver, inserted as a lower filter to the driver stack for accelerated volumes. Dataplex also operates at the file system level to provide file awareness to further optimize system cache performance.  The software is fully transparent to existing software layers.  As it takes a sophisticated adaptive cache approach and learns over time what data is “hot”, the majority of the users will not need any specific SW controls.
After using the drive for a week, I agree with Lin that the overwhelming majority of users will never need to touch a button or twist a dial to ensure high performance from the cache drive. That doesn't mean some users wouldn't benefit from having a greater degree of flexibility. It's also unclear what happens with regard to Windows 8; Microsoft's new file system eschews the "Different drives = Different drive letters" approach in favor of presenting storage as a single pool.


The difference between Nvelo's cache software and other hybrid solutions

For those concerned about how the drive holds up under heavy load, let me say this. Up until now, my Steam installs resided on a separate hard drive. The restrictions on the Nvelo software forced me to migrate that data -- and since my Steam directory is huge and my primary HDD was nearly full, that process required the deletion and relocation of ~600GB of data.

I ran these operations concurrently, including simultaneous copies from C:\ to G:\ and vice versa. At one point, I had 10 file copies going in both directions with a movie playing off E:\. The copies completed flawlessly. The performance boost of having the SSD installed was reserved to files being copied from C:\ (which makes sense), and it eventually vanished as I tasked the mechanicals with more work than they could physically sustain at high speeds.

After all of this, I did have to reboot my system and relaunch a few programs before they sped up again, but the difference was minor.
 
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System Setup, Boot Times
I've been stuck using a 5400 RPM 1TB HDD for most of the past year after circumstances left my primary OS drive (an 80GB Intel SSD) unavailable. I've not gone through the process of switching back, which made my own thoroughly real-world system an ideal testbed for Corsair's Accelerator. I read, write, and transfer quite a bit of data and my Windows 7 install is none-too-pristine.

My current system is a Core i7-920 on a Gigabyte X58A-UD3R motherboard with 16GB of RAM and a GTX 480 installed. My system drive is a Samsung HD103SI, a 5400 RPM (yes, 5400) 1TB affair with an onboard 32MB cache. I ran PCMark 7's storage benchmark to examine storage-related performance in a variety of metrics, but a number of synthetic HDD tests behave oddly -- at least, on my own system -- when the cache accelerator is installed. Since the odd peaks and troughs such tests return don't reflect at all on real-world usage, I've elected not to include them.

Without further ado:

Boot Times:
Boot time is an easy place for an SSD to improve a system's responsiveness. I've subdivided boot time into two categories. The first -- boot-to-login -- is the amount of time it takes for the Windows Logon screen to display after the POST beep. The second, boot-to-desktop, is measured from POST beep to lag-free desktop and includes the boot-to-login measurement. There's a certain degree of subjectiveness to the latter, but not enough to impact the end result.



Knocking the boot-to-logon time in half was impressive on its own, but the Corsair cache drive knocks 80 percent off the hard drive's login-to-desktop processing time. Even if you only reboot once a week, these first few minutes are irritating out of all proportion to the amount of time they actually represent, there are few things more frustrating than watching a normally nimble system struggle to open a web browser while an army of squirrels has a knock-down dragout inside your case.

The boot time improvement is great, but I almost never reboot. Let's examine a few more scenarios.
 
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Application Load Tests, PCMark 7
Next up is a straight performance comparison between various applications and games. Performance was measured with both the hard drive alone and the Accelerator drive installed. One of the potential downsides of an SSD cache drive is that data can be evicted, leaving you dependent on just the hard drive again if you run a program you haven't used in awhile.



The gains are nearly 50% across the board. The performance gain is even greater than it looks -- most of these titles have launch screens that play short videos as part of the game's startup procedure. Since these videos play for a set amount of time regardless, the benefits of the SSD are showing directly where they matter most, specifically loading the game and getting into play.



Next, is PCMark 7. We ran the application's storage benchmark, which gives an overall figure, but also broke down some of the specific results in order to examine where the benefits are (or aren't). In this case, we've got comparative numbers for an OCZ Vertex 3 256GB running the same workload.



Performance in the specific workloads shows exactly the sort of gains we'd hoped it would. While the Vertex 3 remains the fastest solution overall, the hard drive + Corsair Accelerator are far more competitive than the hard drive alone. Having now spent about a week with the drive installed, I can say that there's no performance downside here. In a worst-case scenario, you're left with the same performance that you had before.
 
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Drive Reliability, Data Retention, and Price
For some readers, SSDs are still too new to be trusted, particularly given the shrinking level of data retention in modern Flash. For those concerned about long-term reliability, it probably doesn't help that Novaplex's included help file makes grim reference to the inadvisability of randomly removing the cache drive. We spoke to both Novelo and Corsair regarding these concerns.


How Dataplex keeps data..plexed.

The Dataplex software is specifically designed to work around failed cells, while the drive itself is overprovisioned. Dataplex caches both reads and writes, but the writes are synchronized aggressively with the hard drive. In the unlikely event that the Flash memory begins to fail in large quantities, Dataplex's driver will preemptively disable caching and write all data back to the hard drive before the problem becomes acute enough to potentially threaten user data.

Even a sudden drive contoller failure is unlikely to threaten any user data. Because writes are synchronized quickly, the only way for an SSD failure to kill the operating system (or a vital document/program) is if an update to that specific file is being performed at the exact instant the controller dies. Can this sort of thing happen? Sure. But it's pretty damn rare. In the overwhelming majority of cases, the sudden and irretrievable death of the SSD will result in a normal hard drive boot after the Dataplex software confirms that the cache drive has failed.

The idea that Corsair is selling a specific "cache accelerator" drive could give rise to fears that these drives are somehow made from substandard Flash, or aren't up to the challenge of being Real OS Drives. This is not the case. Without the Dataplex software, the 60GB Accelerator Series drive we've reviewed here is a perfectly ordinary SSD with the same three-year warranty as other Corsair SSDs and competitive read/write performance.

The 60GB Accelerator Series drive we've reviewed today is currently $89.99 at NewEgg. That's in line with the upper-range of 60-64GB drives NewEgg carries, and while a 60GB SSD can be had for less, the difference between the cheapest standalone SSDs and the Corsair Accelerator is only $20. Would we pay $20 for Dataplex's software? Absolutely. In fact, we'd pay more.
 
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Conclusion

Performance Summary: The Corsair Accelerator 60GB drive makes a dramatic difference in the day-to-day, real-world performance of a hard drive. While we very much want to see a version of the software that allows for a certain degree of user configuration, we'll be the first to say that the drive's defaults are well-balanced. Both Corsair and Nvelo take robust data protection seriously, and the software caching algorithms reflect that.

While the technical limitations are a tad frustrating, we're hopeful that the company will modify its policies in the future. Certainly it'll have to make adjustments for Windows 8 in any case.

The hassle of software validation is the only true downside to this product and for now, the hassle is worth it. What we hope is that Nvelo will sincerely reconsider its position after examining what, exactly, it thinks such headaches protect it from. Dataplex is a rare piece of software that really does require specific hardware to make it work properly and there just aren't enough SSDs lying around unused to make pirating the product useful.

We'd recommend the Corsair Accelerator to anyone looking for a low-cost way to boost I/O performance without the hassle of a full system reinstall. You won't get all the benefits of a pure SSD, but you'll get most of them -- and for a very reasonable price.


  • Brings HDD performance up to nearly SSD levels
  • Priced competitively
  • Compatible with most HDD setups.
  • Fire-and-forget configuration makes setup simple
  • Designed to boost performance without risking data integrity
  • Ridiculous validation system inconveniences users, provides no practical benefit. 
  • Technical limitations limit deployment in certain cases.
  • No option to tweak cache priority.


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